CNTs modified geopolymer microspheres loaded with Cu-La bimetallic composites and its photocatalytic performance

CNTs modified geopolymer microspheres loaded with Cu-La bimetallic composites and its photocatalytic performance | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article CNTs modified geopolymer microspheres loaded with Cu-La bimetallic composites and its photocatalytic performance Xiaomin Zhang, Bo Yu, Jing Yang, lianhong zhang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7126019/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract CNTs-modified geopolymer microspheres (GM x wt%CNTs ) were synthesized by adding carbon nanotubes (CNTs) into the geopolymer precursors. And, the Cu-La supported modified geopolymer photocatalysts (1.0%CuO/7.5%La 2 O 3 @GM x wt%CNTs ) were prepared by using GM x wt%CNTs as the carrier. Photocatalytic experiments showed that 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs had the highest photocatalytic activity when CNTs were doped at 0.5 wt%, and the degradation rate of 30 mg/L TCH solution reached 89.51% when irradiated with visible light for 100 min, and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs had good salt resistance, recycling stability and universality, and the free radical capture experiments found that h + was the main active species in this photocatalytic system, with •O 2− was the secondary active species. Characterization analysis showed that by doping CNTs, the conductivity of the material was increased and the resistance of charge transfer at the interface of the material was reduced, which improved the separation efficiency of photogenerated electron-hole pairs, and enabled the catalysts to exhibit a stronger response to visible light. In addition, the CNTs-modified microspheres possessed a more porous structure and larger specific surface area, which provided more active sites for photocatalytic reactions. Geopolymer microspheres Photocatalysis Heterojunction Carbon nanotube Tetracycline hydrochloride Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 1. Introduction The study of the photocatalytic process began in 1972 when scientist Fujishima made the initial discovery that TiO 2 could break down water to create hydrogen when exposed to UV light(Abou-Gamra et al. 2016). Nevertheless, there are still many significant issues with the practical use of photocatalysis in wastewater treatment, such as low utilization of solar energy (Bora et al. 2017), limited photocatalyst recovery(Yaghoubi et al. 2024 ), high cost(Prieto-Rodriguez et al. 2012 ), and vulnerability to secondary pollutants(Sun et al. 2025 ), among others. Therefore, research on inexpensive(Ahmad et al. 2023 ), effective, environmentally friendly(Ravi et al. 2025), and easily recyclable photocatalysts is extremely important(Liu et al. 2023 ). Geopolymer, a new kind of three-dimensional inorganic polymer material, was first identified and named by French scientist Professor Davidovits in 1978(Davidovits 1989 ). Its raw materials are inexpensive and readily available, typically consisting of silicate salts like fly ash, gangue, slag, and metakaolin(Ambikakumari Sanalkumar et al. 2021, Xing et al. 2024 ). It is consists of a porous three-dimensional skeleton of aluminium-oxygen tetrahedra and silica-oxygen tetrahedra alternately connected with shared oxygen atoms.(Kočí et al. 2022), which has excellent ion exchange(Clausi et al. 2023 , Medri et al. 2022 ), stability(Han et al. 2024 , Shumuye et al. 2024 ), and adsorption(Sarmento et al. 2006 ). Because of their low cost(Ji et al. 2021 ), low CO 2 emission, low energy consumption(Ma et al. 2023 ), and environmental friendliness(Maiti et al. 2020 ), geopolymers have drawn a lot of attention recently in a variety of fields(Bai et al. 2024 ), including heavy metal fixation(Ji et al. 2019), adsorbent materials(Wei et al. 2023 ), membrane materials, photocatalytic materials(Dong et al. 2022 ), etc. In particular, geopolymers have been widely used as a new type of catalytic material in various catalytic reactions(Muñoz et al. 2017 ). To overcome the drawbacks of traditional nano-polymers, which are prone to secondary pollution(Sarkar et al. 2020 , Yan et al. 2023), have a low recycling rate, and are easily agglomerated, photocatalytic active factors are introduced into the geopolymer skeleton(Baig et al. 2017 , Ranjbar et al. 2020), this will have a synergistic effect with the geopolymer, improving the photocatalyst's recycling rate, lowering reaction costs, and providing more active sites for the photocatalytic reaction(Barbarey et al. 2024 , Botti et al. 2022 ). For loaded photocatalysts, more efficient separation of photogenerated carriers can be achieved by enhancing the electrical conductivity of the carrier so that the carrier has the role of transporting photogenerated electrons(Torralvo et al. 2018 ), allowing it to act as an electron acceptor and increasing the electron migration rate(Hasija et al. 2021 , Zainudin et al. 2010 ). By doping graphene, Zhang et al(Zhang et al. 2017 ). created conductive graphene-based geopolymer-loaded CuO composites for the first time. They discovered that graphene's exceptional charge-trapping capability can increase the conductivity of the geopolymer carrier, which in turn speeds up the separation of photogenerated electron-hole pairs and boosts photocatalytic activity. A new conductive carbon fiber/fly ash-based geopolymer composite was created and synthesized by Pan et al(He et al. 2020 ). It was discovered that the conductive carbon fibers were evenly embedded in the geopolymer matrix and that doping the carbon fibers increased the conductivity of the geopolymer to 8.44 S/m, 44,000 times higher than that of the geopolymer without the carbon fiber. Additionally, the carbon fibers were able to efficiently capture and transfer the photogenerated electrons in the photocatalytic reaction system, which could increase the separation rate of photogenerated electron-hole pairs and boost photocatalytic performance. Because each of the C atoms in carbon nanotubes (CNTs) has an unpaired electron in the P orbital, these carbon isotope isomers are arranged in cylindrical nanostructures and have exceptional electrical conductivity(Li 2021 , Wang et al. 2017 , Wieland et al. 2021 ). Because of their high specific surface area and exceptional electrical conductivity(Phin et al. 2020 ), carbon nanotubes (CNTs) may quickly absorb photogenerated electrons from semiconductor photocatalysts in a photocatalyst system(Mateen et al. 2023 ), increasing the pace at which photogenerated light-generated carriers are separated(Amaya-Galván et al. 2025 , Wang et al. 2024 , Zhang et al. 2018a ). CNTs-modified geopolymer microspheres (GM CNTs ) were prepared by doping CNTs into the geopolymer precursor, so that the microspheres would have the role of transporting electrons to improve the electron mobility. In this study, the Cu-La supported modified geopolymer photocatalyst (1.0%CuO/7.5%La 2 O 3 @ GMxwt%CNTs ) were prepared by constructing heterojunctions using ion-exchange properties of microspheres and van der Waals forces with La(NO 3 ) 3 as the La source and Cu(NO 3 ) 2 as the Cu source. The degradation of 50 mL of TCH solution at a concentration of 30 mg/L, catalyzed by visible light, was used to assess the photocatalytic activity. 2. Experimental section 2.1 Materials Metakaolin: (Guangzhou Changyu Chemical Co., Ltd, model 1305, white powder) The chemical composition of metakaolin was analyzed by X-ray fluorescence characterization. Its chemical composition is mainly SiO 2 , Al 2 O 3 , CaO, and Na 2 O, and contains traces of MgO, Fe 2 O 3 , K 2 O, etc. Alkali exciter: (Jiashan Yourui Refractories Co., Ltd.) water glass (liquid sodium silicate) with an initial modulus of 3.26, which is adjusted to 1.2 by adding NaOH and deionized water. 2.2 Preparation of GM x wt%CNTs CNTs modified geopolymer microspheres (GM x wt%CNTs ) were prepared by using suspension-dispersion technique using metakaolin and alkali exciters as precursors by doping CNTs into the precursors in the following experimental steps: A certain mass of CNTs was doped into the metakaolin and stirred to make a homogeneous mixture, and then 8.5 g of alkali exciter was added into the precursor and stirred for 15 min to make a full reaction to form a geopolymer slurry. The slurry was slowly dripped into hot dimethicone oil (80°C) at a stirring speed of 800 r/min and stirred for 10 min, and the slurry was subjected to shear force in the stirred hot silicone oil, and microspheres were formed through suspension-dispersion. Then the beaker containing microspheres and dimethicone oil was moved to an 80°C oven to fully cure and maintain for 24h, and then filtered to separate the GM x wt% CNTs , washed with cyclohexane several times to fully remove the silicone oil on the surface of microspheres, and then moved to a 70°C oven to dry for 12h, and then calcinated by a tube furnace at 500°C for 2h (argon atmosphere). Then wash with deionized water several times to fully wash away the NaOH on the surface of the microspheres, and then put into the oven at 60°C to dry for 12h. Finally, the microspheres were sieved with 100 and 300 mesh sieves to obtain 100 ~ 300 mesh GM CNTs , respectively. 2.3 Preparation of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs Using GM CNTs as carriers, a certain amount of Cu(NO 3 ) 2 was weighed and dissolved in 20 mL of deionized water and sonicated for 15 min, and then 0.5 g of 7.5% La 2 O 3 @GM was added to the Cu(NO 3 ) 2 solution, which was stirred for 6 h at room temperature, and Cu 2+ was loaded onto the 7.5% La 2 O 3 @GM by using the ion-exchange properties of the microspheres and the effect of van der Waals' force on its surface. Then the Cu(NO 3 ) 2 loaded photocatalytic composite of 7.5% La 2 O 3 @GM (Cu(NO 3 ) 2 /7.5% La 2 O 3 @GM) was obtained by evaporation with stirring in a water bath at 80°C. Finally, the Cu(NO 3 ) 2 /7.5% La 2 O 3 @GM was moved to a muffle furnace and calcined at 500°C for 5 h to obtain the geopolymer-loaded Cu-La bimetallic photocatalytic composites 1.0% CuO/7.5% La 2 O 3 @GM x wt% CNTs . 2.4 Characterization analysis X-ray diffraction (XRD): characterizing the crystal structure of the catalyst; Low-temperature nitrogen adsorption-desorption isothermal curve (BET): testing the specific surface area and other information of the catalyst; X-ray photoelectron spectroscopy (XPS): testing the surface element composition, valence and other information of the catalyst; Scanning electron microscopy (SEM): characterizing the surface morphology of the catalyst; Transmission electron microscopy (TEM): characterizing the microscopic morphology, particle size and distribution of catalysts; UV-vis diffuse reflectance spectroscopy (UV-vis DRS): testing the wavelength range of light absorbed by the catalyst and additional information; Photoluminescence spectroscopy (PL): characterizing the photogenerated electron-hole recombination rate of the catalyst; Infrared spectroscopy (FT-IR): analyzing the characteristic functional groups of catalysts and other information. 2.5 Photocatalytic activity To assess the photocatalytic activity of the samples, the photocatalytic degradation of TCH solution was selected in this paper. To do this, 50 mL of a specific concentration of TCH (30 mg/L) solution was pipetted precisely using a measuring cylinder and then added to the photocatalytic reaction device. Next, 0.1 g of photocatalyst was weighed into the photocatalytic device that was equipped with the TCH solution, and simultaneously, the electronic stirrer was activated. Photocatalysis starts with 30 min of light avoidance to bring the reaction to adsorption-desorption equilibrium, and then a xenon lamp is switched on at the end of the dark adsorption, while condensate is passed through. Then 8 mL of reaction solution was taken in a 10 mL centrifuge tube every 20 min, and the supernatant was taken in a 10 mm cuvette by centrifugation at 4000 r/min, and the absorbance (A t ) of the photocatalytic reaction solution was measured at the moment t at the wavelength of maximum absorption of the TCH (λ = 357 nm), using a visible spectrophotometer. The degradation rate of the TCH solution was calculated by Eq. ( 1 ). The proposed first-order kinetic constants of the photocatalytic reaction were calculated from Eq. ( 2 ). Where η is the degradation rate of the TCH solution, A 0 is the initial absorbance of the TCH solution, A t is the absorbance of the TCH solution at time t, k is kinetic constant (min − 1 ), C t is the concentration of TCH solution at time t, and C 0 is the concentration of TCH solution at the initial time. 3. Results and discussion 3.1 Microscope analysis The SEM images of the catalysts 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs are shown in Fig.1(a) and Fig.1(b). Both materials showed high sphericity, dense and compact microsphere structures, and rough surfaces containing a large number of pore structures. However, by comparison, it was found that the surface roughness of the geopolymer microspheres doped with CNTs was larger and contained more pore structures, suggesting that the doping of CNTs could improve the morphological structure of the microspheres and give the material a larger specific surface area, which could provide richer active sites for the photocatalytic reaction. Figure 1(c) shows the elemental mapping of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs . The C, Cu, and La elements are uniformly dispersed, which indicates that CNTs, Cu, and La elements are highly dispersed in the microspheres. The distribution of grains on the surface of the photocatalytic microspheres and the crystal spacing were analyzed by TEM characterization to determine the presence of CuO and La 2 O 3 in 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs and their distribution. As shown in Fig. 2(a), the microsphere surface was loaded with a large number of grains with uniform distribution, indicating that CuO and La 2 O 3 were uniformly dispersed on the microsphere surface. The crystallographic spacing of the corresponding grains in the two selected regions in Fig. 2(b) are 0.311 nm and 0.273 nm, respectively, with 0.311 nm attributed to the {101} crystallographic plane of La 2 O 3 (Huang et al. 2019) , and 0.273 nm attributed to the {110} crystallographic plane of CuO(Zhang et al. 2018b), which confirms the presence of CuO and La 2 O 3 on the surface of the microspheres with a homogeneous distribution, and suggests that 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs photocatalytic composites have been successfully prepared. 3.2 EDS analysis To determine the elemental composition of the photocatalytic microsphere surface, the EDS energy spectrum of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs was tested. As shown in Fig. 3, the binding energies of 0.28 KeV, 0.52 KeV, 1.04 KeV, 1.48 KeV, 1.74 KeV, 2.14 KeV, 4.64 KeV, and 8.04 KeV corresponded to the elements C, O, Na, Al, Si, Au, La, and Cu, where the detection of elemental Au is attributed to the surface gold spraying of sample 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs (since non-conductive samples need to be surface sprayed to be tested), O, Na, Al and Si elements attributed to the solid inclusion in the geopolymer precursor biotite kaolinite, Cu and La elements are attributed to CuO and La 2 O 3 , and C is attributed to CNTs, and combined with other characterization analyses, O also corresponds to the O element in CuO and La 2 O 3 . 3.3 BET analysis The low-temperature N 2 adsorption-desorption curves of 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs are shown in Fig. 4(a), and the adsorption curves of the two materials increase slowly within the low-pressure section P/P 0 =0.025~0.85, which indicates that the amount of nitrogen adsorbed in the low-pressure stage is gradually increasing, and the adsorption curves rise steeply in the section P/P 0 =0.85 ~ 0.98, and the isothermal adsorption curve and the desorption curves in this stage form a typical H3 type hysteresis loop, which indicates the existence of a large number of mesopores in the geopolymer microspheres. According to the classification criteria of the standard isotherms for physical adsorption, the adsorption-desorption isothermal curves of 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs belonged to the isotherms of class IV, and there was no significant change in the adsorption-desorption isothermal curves of the two materials. Fig. 4(b) shows the pore size distribution curves of 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs . As shown, the pore size distribution of the two samples is in the range of 12 ~ 70 nm, which also indicates that a large number of mesopores exist in 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs . These pores, on the one hand, can allow the microspheres to have a large specific surface area and provide abundant active sites for this photocatalytic system, and on the other hand, they can reduce the mass-transfer resistance during the reaction process, so that the photocatalytic reactants and reaction products to pass through these pores quickly. Table 1 shows the specific surface area, pore volume, and pore size data of 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs . As shown in Table 1, 1.0%CuO/7.5%La 2 O 3 @GM has a specific surface area of 35.70 m 2 ⸱g -1 , a pore volume of 0.19 cm 3 ⸱g -1 and pore size of 18.00 nm, whereas 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs has a specific surface area of 41.41 m 2 ⸱g -1 , a pore volume of 0.21 cm 3 ⸱g -1 and a pore size of 33.09 nm. The pore diameter of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs is bigger than those of 1.0%CuO/7.5%La 2 O 3 @GM, which shows that the morphological structure of microspheres can be improved by doping CNTs, which gives them a larger specific surface area and can provide more active sites for the photocatalytic reaction system. Table 1 Specific surface area, pore volume, and pore size of 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs catalyst BET(m 2 ⸱g -1 ) pore volume(cm 3 ⸱g -1 ) pore size(nm) 1.0%CuO/7.5%La 2 O 3 @GM 35.70 0.19 18.00 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs 41.41 0.21 33.09 3.4 XPS analysis Fig. 5 shows the XPS spectra of GM、1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs . The elemental composition of the samples as well as the chemical valence states were analyzed. Figure 5(a) shows the total spectra of the three materials at binding energies of 74.0 eV, 102.0 eV, 531.0 eV, 835.0 eV, 934.0 eV, and 1072.0 eV corresponding to the elements of Al, Si, O, La, Cu, and Na in sample 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs . Fig. 5(b) shows the high-resolution spectrum of La 3d for 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs . There are more obvious spin-orbit splitting peaks in the high-resolution spectrum of La 3d, and the splitting peaks of each spin-orbit splitting peaks multiply and cleave into two splitting peaks, which corresponds to La 3d 5/2 and La 3d 3/2 in La 2 O 3 at the binding energies of 835.0 eV/838.5 eV and 851.9 eV/855.5 eV. Fig. 5(c) shows the Cu 2p high-resolution spectrum of c. The binding energies 933.2 eV and 953.2 eV correspond to Cu 2p 3/2 and Cu 2p 1/2, respectively, with a peak spacing of 19.9 eV and accompanied by two satellite peaks, which suggests the presence of Cu 2+ in the form of CuO(Li et al. 2023). Therefore, XPS analysis confirmed the presence of La 2 O 3 and CuO in the samples, indicating that the 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs photocatalytic composites were successfully prepared. 3.5 UV–vis DRS analysis The response properties of photocatalytic materials GM, 7.5%La 2 O 3 @GM, 1.0%CuO/7.5%La 2 O 3 @GM, and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs to light were investigated by UV-Vis DRS characterization. As shown in Fig. 6 (a), all four samples showed strong light absorption in the UV region, with 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs having stronger light absorption properties than 1.0%CuO/7.5%La 2 O 3 @GM in the visible region (400 ~ 800 nm). It can be seen that by doping CNTs into the geopolymer microspheres, the visible light absorption range of the catalyst can be significantly increased, making it more photoresponsive to the visible region, reducing the energy needed for electron migration and achieving the enhancement of its photocatalytic activity. Fig. 6 (b) shows the forbidden bandwidth of the catalyst calculated by Tauc's equation (Eq. 3), and the forbidden bandwidth of the semiconductor is obtained by linear extrapolation from Eq. Eg = 1240/ λg . As shown in Fig. 6 (b), the forbidden bandwidths of GM, 7.5%La 2 O 3 @GM, 1.0%CuO/7.5%La 2 O 3 @GM, and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs are calculated by linear extrapolation to be 3.28eV, 3.22eV, 1.80eV, 0.39eV, respectively. Therefore, the doping of CNTs in microspheres resulted in a certain magnitude reduction in the forbidden band width of catalyst 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs , which allowed it to be excited by longer wavelengths and had a stronger photoresponsivity, achieving the effect of improving its photocatalytic performance. Where α denotes the absorption coefficient, h denotes Planck's constant (1.6 × 10 −19 ), v denotes the optical frequency (Hz), A denotes the proportionality constant; E gap denotes the band gap width of the photocatalyst (eV). 3.6 PL analysis The PL spectra of GM, 7.5%La 2 O 3 @GM, 1.0%CuO/7.5%La 2 O 3 @GM, and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs were tested at an excitation wavelength of 250 nm, as shown in Fig. 7. The PL spectra of the photocatalytic materials were tested to investigate the separation of photogenerated carriers of the catalysts. The order of peak intensities in the PL spectra of the four materials is GM > 7.5%La 2 O 3 @GM > 1.0% CuO/7.5%La 2 O 3 @GM > 1.0%CuO/7.5%La2O3@GM 0.5%CNTs . Among them, 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs exhibit the weakest fluorescence intensity compared to the other three materials, which is attributed to the fact that the doping of CNTs in the geopolymer precursor increases the conductivity of the material and enhances the photogenerated carrier mobility rate to achieve the enhancement of the photocatalytic effect of the material. 3.7 EIS analysis Electrochemical impedance spectroscopy (EIS) responds to the charge transfer ability at the interface of photocatalytic materials. The smaller the arc radius of the EIS spectrum, the higher the conductivity and the lower the resistance of charge transfer at the interface of the sample, i.e., the higher the efficiency of photogenerated electron-hole separation. Therefore, to investigate the effect of CNTs doping on the conductivity of photocatalytic materials, the EIS spectra of 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs were characterized and analyzed. As shown in Fig. 8, the radius of arc of Nyquist curve of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs is smaller than that of 1.0%CuO/7.5%La 2 O 3 @GM, i.e., the conductivity of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs is lower than that of 1.0%CuO/7.5%La 2 O 3 @GM. 4. Evaluation of photocatalytic performance 4.1 Photocatalytic degradation of TCH The photocatalytic degradation performance of the four materials was analyzed by photocatalytic degradation of 50 mL of TCH solution at a concentration of 30 mg/L. The comparative photocatalytic performance plots of GM, nano-TiO 2 , 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs and the fitted plots of the proposed first-order kinetic constants for the degradation of TCH were tested, respectively, as shown in Fig. 9 (a) and (b). As shown in Fig. 9 (a), the strong and weak photocatalytic performances of the four photocatalytic materials for degrading TCH solution were in the order 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs >1.0%CuO/7.5%La 2 O 3 @GM > nano-TiO 2 > GM, 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs had the highest photocatalytic activity for degrading TCH solution, and the degradation rate of 50 mL of TCH solution with concentration of 30 mg/L could reach 89.51% when the reaction was carried out for 100 min. The adsorption rate of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs on TCH was 37.45% after 130 min of dark reaction, and the adsorption-desorption equilibrium was reached after 30 min of dark reaction. Figure 9 (b) shows the fitted results of the proposed primary kinetic constants for the degradation of TCH solution by the four catalysts, with the proposed primary kinetic constants of 0.00316 min − 1 , 0.00772 min − 1 , 0.01512 min − 1 , and 0.01893 min − 1 for GM, nano-TiO 2 , 1.0%CuO/7.5%La 2 O 3 @GM and 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs , the proposed first-order kinetic constants of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs were the largest indicating the fastest degradation rate to TCH solution and the proposed first-order kinetic constants were 1.25 times higher than that of 1.0% CuO/7.5%La 2 O 3 @GM. 4.2 Effect of CNTs doping on the photocatalytic performance of 1.0%CuO/7.5%La 2 O 3 @GM x wt%CNTs To investigate the optimal doping amount of CNTs, a total of 1.0% CuO/7.5% La 2 O 3 @GM x wt% CNTs were tested for photocatalytic degradation of TCH at doping amounts of 0.1 wt%, 0.3 wt%, 0.5 wt% and 0.7 wt%, respectively. The experimental results are shown in Fig. 10 (a) of The photocatalytic activity of 1.0%CuO/7.5%La 2 O 3 @GM 0.5%CNTs was highest when the CNTs were doped at 0.5 wt%, and the degradation rate of TCH solution was 89.51% when the photocatalytic reaction lasted for 100 min. Figure 10 (b) shows the fitted plot of the proposed first-order kinetic constants for 1.0% CuO/7.5%La 2 O 3 @GM x wt% CNTs photocatalytic degradation of TCH, and the proposed first-order kinetic constants for 1.0% CuO/7.5%La 2 O 3 @GM 0.5% CNTs degradation of TCH were the largest when the doping amount of CNTs was 0.5 wt%. Therefore, the experimental results showed that the optimum doping amount of CNTs was 0.5 wt%. The effect of coexisting anions Cl − , NO 3− , PO 4 3− , SO 4 2− , and CO 3 2− on the photocatalytic activity was investigated by adding 1 mmol of NaCl, NaNO 3 , Na 3 PO 4 , Na 2 SO 4 , and Na 2 CO 3 , respectively, to the TCH solution. As shown in Fig. 11 , the photocatalytic activity of 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs was enhanced when PO 4 3− and CO 3 2− were present in this system, which was attributed to the fact that the PO 4 3− and CO 3 2− made the TCH solution alkaline, which favored the production of more •OH under alkaline conditions and enhanced the photocatalytic performance of the system. However, these co-existing anions had little effect on the system, and therefore the 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs showed good salt resistance. 4.4 Evaluation of Recycling Stability To investigate the stability and recyclability of the photocatalytic material 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs , the stability of 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs was investigated by centrifuging, washing and vacuum drying the samples at the end of the photocatalytic reaction and repeating the photocatalytic performance evaluation experiment under the same experimental conditions. As shown in Fig. 12 , the degradation rate of 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs on TCH solution can still reach 72.35% after 4 photocatalytic recycling, and it exhibits good stability. However, the degradation rate of the material to the TCH solution decreased somewhat after 4 cycles, which may be due to some loss of the catalyst in the process of recycling, or since the fact that some of the undegraded TCH molecules adsorbed on the surface of the microspheres in the photocatalytic reaction remained on the surface of the catalyst after recycling, which led to the decrease of the active sites of the catalyst. 4.5 Universal Performance Evaluation The practical application value of photocatalyst 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs was explored by evaluating the photocatalytic performance of the photocatalytic materials for different organic pollutants. The photocatalytic degradation performance of the photocatalytic materials was investigated for TCH, MB, MR, and MG, respectively, according to the photocatalytic performance evaluation method in Section 2.5 . The experimental results are shown in Fig. 13 . The degradation rates of 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs on TCH, MB, MR and MG were 89.51%, 94.86%, 88.27% and 92.24%, and the photocatalytic material 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs showed good photocatalytic degradation of these four organic pollutants, which indicates that the material has excellent universality and has certain application value. 4.6 Active Species Detection Experiment To investigate the catalytic mechanism of 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs photocatalytic degradation of TCH, IPA, EDTA-2Na, and ASA were added as •OH, h + , and •O 2− radical trapping agents, respectively, to the system degrading TCH solution. As shown in Fig. 14 , the photocatalytic degradation of TCH solution did not decrease significantly when the •OH radical capture agent IPA was added to the photocatalytic reaction system, but when the h + and •O 2− radical capture agents EDTA-2Na and ASA were added to the photocatalytic reaction system, the degradation rate of the sample to TCH solution decreased more. The degradation rate of the sample to the TCH solution decreased more, and the effect size of these three radical trappers was EDTA-2Na > ASA > IPA, indicating that h + was the main active species and •O 2− was the secondary active species in this system. 4.7 Photocatalytic Mechanism Analysis The photocatalytic mechanism of 1.0% CuO/7.5%La 2 O 3 @GM 0.5%CNTs is shown in Fig. 15 . Since La 2 O 3 and CuO form a type I heterojunction, h + on La 2 O 3 VB can jump to VB of CuO, and e − on La 2 O 3 CB will jump to CB of CuO. The CNTs in the geopolymer microspheres can act as electron acceptors, and e − can be migrated from the CB of CuO to the CNTs, and the e − migrated to the CNTs reacts with the O 2 molecules adsorbed on the photocatalytic microspheres to generate •O 2− , and the h + on the CuO VB reacts with the H 2 O adsorbed on the photocatalytic microspheres to generate -OH and H + , the h + , •O 2− and •OH with strong oxidative properties achieve the oxidative decomposition of TCH molecules. The conductivity of the microspheres was increased by the introduction of CNTs so that they acted as electron acceptors and provided channels for the migration of photogenerated electrons, which inhibited the recombination of photogenerated carriers and improved the photocatalytic activity of the samples. In addition, the specific surface area and pore structure of the photocatalytic materials were improved by doping CNTs, and the multi-porous structure and excellent adsorption of the microspheres provided more active sites for the photocatalytic reaction, and the three-dimensional skeleton structure of the geopolymer contained Bronsted acidic sites (Si-O-H + ), which could be combined with h + to generate •OH, which has the effect of promoting the effective separation of h + and e −(Wang et al. 2018) . Thus, the photocatalytic activity of the composites was further enhanced by the doping of CNTs in the geopolymer microspheres. 5. Conclusion In this paper, CNTs-modified geopolymer microspheres (GM x wt%CNTs ) were prepared by a suspension-dispersion technique using metakaolin and alkali exciters as raw materials, and carbon nanotubes (CNTs) were doped into the precursor to improve the electrical conductivity and morphology structure of geopolymers. Then the photocatalytic material 1.0%CuO/7.5%La 2 O 3 @GM x wt%CNTs was prepared in the carrier of GM x wt%CNTs .The photocatalytic activity was evaluated by visible-light catalytic degradation of TCH solution, and the effect of the optimal doping amount of CNTs (wt%) on the photocatalytic performance was explored. The experimental results showed that the photocatalytic activity of 1.0%CuO/7.5%La 2 O 3 @GM x wt%CNTs was optimal when the doping amount of CNTs was 0.5 wt%, and the degradation performance of CNTs could reach 89.51% of 50 mL of 30 mg/L TCH solution within 100 min under the irradiation of can be light, and the proposed first-order kinetic constant of its degradation of TCH was 1.25 times higher than that of undoped CNTs. The CNTs-modified microspheres have a more porous structure and larger specific surface area, which can provide more active sites for the photocatalytic reaction. After doping CNTs into the geopolymer precursor, the conductivity of the samples increased, the photocatalytic materials showed stronger absorption of visible light, the forbidden bandwidth decreased from 1.80 to 0.39 eV, and the recombination of the photogenerated electron-hole pairs was significantly inhibited. As a result, the 1.0%CuO/7.5%La 2 O 3 @GM 0.5% CNTs exhibited higher photocatalytic activity. Declarations Acknowledgements This work was financially supported by the Local Science and Technology Development Fund Projects Guided by the Central Government of China (2021ZYD0060), the Science and Technology Project of Southwest Petroleum University (2021JBGS03), the Chengdu International Science and Technology Cooperation Fund （2020GH0200069HZ）. Funding Open access funding provided by Science and Technology Project of Southwest Petroleum University (2021JBGS03). This research was supported by Chengdu International Science and Technology Cooperation Fund （2020GH0200069HZ）. Authors’ Contributions All authors contributed to the conception and design of the study.Methodology, software, validation, investigation, data curation, formal analysis, and writing-original draft were conducted by Xiaomin Zhang, with revisions provided by all authors.Bo Yu and Jing yang contributed to theresources, data Curation, visualization, investigation, and formal analysis. Lianhong Zhangcontributed to the methodology, funding acquisition, resources, writing-review & editing, and project administration. The first draft of the manuscript was written by Xiaomin Zhang, and all authors reviewed, provided feedback, and approved the final version of the manuscript. Corresponding author Correspondence to Lianhong Zhang. Ethical approval This is not applicable. Consent to participate This is not applicable. Consent to publish This is not applicable. 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Int J Hydrog Energy 42:20589–20598 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 03 Aug, 2025 Reviewers invited by journal 03 Aug, 2025 Editor invited by journal 24 Jul, 2025 Editor assigned by journal 18 Jul, 2025 First submitted to journal 17 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7126019","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494841985,"identity":"e9d32ff8-9baa-4ac7-a651-f726508ec990","order_by":0,"name":"Xiaomin Zhang","email":"","orcid":"","institution":"Southwest Petroleum University SWPU: Southwest Petroleum University","correspondingAuthor":false,"prefix":"","firstName":"Xiaomin","middleName":"","lastName":"Zhang","suffix":""},{"id":494841986,"identity":"2c6c2842-1559-47ad-b1d1-9181ff6f3e03","order_by":1,"name":"Bo Yu","email":"","orcid":"","institution":"Southwest Petroleum University SWPU: Southwest Petroleum University","correspondingAuthor":false,"prefix":"","firstName":"Bo","middleName":"","lastName":"Yu","suffix":""},{"id":494841987,"identity":"cf51ba39-52dd-4e88-87c6-628c9827f45a","order_by":2,"name":"Jing Yang","email":"","orcid":"","institution":"SWPU: Southwest Petroleum University","correspondingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Yang","suffix":""},{"id":494841988,"identity":"fdd2f7a3-c7d0-4a59-a81a-32ba17ffe009","order_by":3,"name":"lianhong zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFUlEQVRIiWNgGAWjYDACCRBRIAFlVEjIybM3Nj78QFCLAUzLGRtjw57DzcYShLVAGYxtaYkNN9LbBHjw6JCf3fzs4RcDC3lz6eZjD7+wHWZsnPmwDajfTk63AbsWxjnHzI1lDCQMd845lm4sw3OYmV06se1BAUOysdkB7FqYJRLMpCUMJBg33MgBMiQOszHOTmwH+u1A4jYcWtgk0r+BtNhDtBgc5mG4ebBNggePFh6JHDPJDwYSiSAtkh8S0iQYbjDi1yIhkVMmDQzk5A030tKkGQ7YGBj2JAID2QC3X+RnpG+T/FFRZ7vhRvIxyZ//JOrnsx9/+PBDhZ0cLi3gIOBBZ0BiCg9g/IHOGAWjYBSMglGADAA+M1tGwBxWdAAAAABJRU5ErkJggg==","orcid":"","institution":"Southwest Petroleum University SWPU: Southwest Petroleum University","correspondingAuthor":true,"prefix":"","firstName":"lianhong","middleName":"","lastName":"zhang","suffix":""}],"badges":[],"createdAt":"2025-07-15 04:10:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7126019/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7126019/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88515268,"identity":"83999924-9ec8-4680-909e-de4936b0593b","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":344756,"visible":true,"origin":"","legend":"\u003cp\u003e(a) (b) SEM images of \u003ca href=\"mailto:1.0%25CuO/7.5%25La2O3@GM\"\u003e1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003c/a\u003e and \u003ca href=\"mailto:1.0%25CuO/7.5%[email protected]%25CNTs\"\u003e1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/a\u003e, (c) Element mapping diagram of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/249a15b57a8b0f917f82da93.jpg"},{"id":88515269,"identity":"d3330357-fb97-4080-93c2-11313785febf","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":136548,"visible":true,"origin":"","legend":"\u003cp\u003eTEM images of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/2d7de8405118710ad9507e9f.jpg"},{"id":88515266,"identity":"b0c9eac6-2d27-4cd9-a545-88891f6ea401","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":22100,"visible":true,"origin":"","legend":"\u003cp\u003eThe EDS energy spectrum of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/123e97d19efdab48e0c0558e.jpg"},{"id":88515267,"identity":"101580fd-6ff0-4a62-9fb6-0b5a1816eb9c","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":116839,"visible":true,"origin":"","legend":"\u003cp\u003eLow temperature N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isothermal curves for 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e(a); pore size distribution curves (b)\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/c60a7a7310c8ea8291b03407.jpg"},{"id":88516342,"identity":"c97acc17-918c-41e6-bde8-d658c1a352bd","added_by":"auto","created_at":"2025-08-07 08:54:19","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":170041,"visible":true,"origin":"","legend":"\u003cp\u003eXPS gross spectra of different materials (a); fine spectra of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e La3d (b), Cu 2p (c)\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/8b6b0e79231a7210cce1da51.jpg"},{"id":88516340,"identity":"b66ffc63-92d1-41e9-9410-4c7eb0671ace","added_by":"auto","created_at":"2025-08-07 08:54:19","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":94074,"visible":true,"origin":"","legend":"\u003cp\u003eUV-Vis spectra of GM, 7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e (a); Tauc plot (b)\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/515c4e524e8e06ff3656315b.jpg"},{"id":88516727,"identity":"f03e5734-c3ed-44fa-9a51-50a6a0c420d9","added_by":"auto","created_at":"2025-08-07 09:02:19","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":33721,"visible":true,"origin":"","legend":"\u003cp\u003ePL spectra of GM, 7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, and \u003ca href=\"mailto:1.0%25CuO/7.5%[email protected]%25CNTs\"\u003e1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/a\u003e\u003c/p\u003e","description":"","filename":"Picture7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/7162842137867bfbcb25d22b.jpg"},{"id":88515283,"identity":"1667e39a-a145-446f-adfc-7d94746169c8","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":21726,"visible":true,"origin":"","legend":"\u003cp\u003eEIS spectra of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Picture8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/99371425a5be1eb49aef0cf6.jpg"},{"id":88515273,"identity":"68732e47-556c-4b8e-b904-5c36f4bf9ace","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":103935,"visible":true,"origin":"","legend":"\u003cp\u003ePhotocatalytic degradation of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e, 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, nano-TiO\u003csub\u003e2\u003c/sub\u003e and GM TCH solution performance plot (a); fitted plot of fitted first order kinetic constants for degraded TCH solution (b)\u003c/p\u003e","description":"","filename":"Picture9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/b843ef9d1fcd2b15541a56e7.jpg"},{"id":88517637,"identity":"6c37e2e1-71b5-464f-b249-7977522bab0f","added_by":"auto","created_at":"2025-08-07 09:10:19","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":97465,"visible":true,"origin":"","legend":"\u003cp\u003ePerformance plot of photocatalytic degradation of TCH solution with 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e at different CNTs doping (a); fitted plot of the proposed first-order kinetic constants of the degraded TCH solution (b)\u003c/p\u003e","description":"","filename":"Picture10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/b169b09631e863255a7e5844.jpg"},{"id":88516345,"identity":"6e97511b-c8cf-4aa1-9349-25b378997ff1","added_by":"auto","created_at":"2025-08-07 08:54:19","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":26753,"visible":true,"origin":"","legend":"\u003cp\u003ePlot of the effect of coexisting anions on 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e photocatalytic performance\u003c/p\u003e","description":"","filename":"Picture11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/bc405a1abf03d8c35aaf7e01.jpg"},{"id":88515277,"identity":"129951cb-738f-48f2-9d64-04aea777650c","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":31101,"visible":true,"origin":"","legend":"\u003cp\u003e1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e photocatalytic degradation of TCH solution cycling performance graphs\u003c/p\u003e","description":"","filename":"Picture12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/276f130825ae38db5d006ea4.jpg"},{"id":88516350,"identity":"1ecfca38-f52a-499f-81f4-11dcdfab5c3c","added_by":"auto","created_at":"2025-08-07 08:54:19","extension":"jpg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":23286,"visible":true,"origin":"","legend":"\u003cp\u003e1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e photocatalytic degradation performance of different organic pollutants\u003c/p\u003e","description":"","filename":"Picture13.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/0e9eb919839f6db7f94d9753.jpg"},{"id":88516731,"identity":"46f1fb00-3374-483b-aeab-824f541ba804","added_by":"auto","created_at":"2025-08-07 09:02:19","extension":"jpg","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":19904,"visible":true,"origin":"","legend":"\u003cp\u003eVisible photocatalytic degradation of TCH by 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e in the presence of different radical trappers performance map\u003c/p\u003e","description":"","filename":"Picture14.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/1ee18d1f59b23413cf00d0ba.jpg"},{"id":88515281,"identity":"4be3137c-6773-47c6-8032-ea7a891aca01","added_by":"auto","created_at":"2025-08-07 08:46:19","extension":"jpg","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":60808,"visible":true,"origin":"","legend":"\u003cp\u003ePhotocatalytic mechanism diagram of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Picture15.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/e52f85672a46e84f41b2ee14.jpg"},{"id":89062852,"identity":"8f4c1193-9b6b-4657-a9fc-64b300ae51b9","added_by":"auto","created_at":"2025-08-14 09:47:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2238414,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7126019/v1/5f6441f4-979c-44e1-88ec-79385865225a.pdf"}],"financialInterests":"","formattedTitle":"CNTs modified geopolymer microspheres loaded with Cu-La bimetallic composites and its photocatalytic performance","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe study of the photocatalytic process began in 1972 when scientist Fujishima made the initial discovery that TiO\u003csub\u003e2\u003c/sub\u003e could break down water to create hydrogen when exposed to UV light(Abou-Gamra et al. 2016). Nevertheless, there are still many significant issues with the practical use of photocatalysis in wastewater treatment, such as low utilization of solar energy (Bora et al. 2017), limited photocatalyst recovery(Yaghoubi et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), high cost(Prieto-Rodriguez et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), and vulnerability to secondary pollutants(Sun et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), among others. Therefore, research on inexpensive(Ahmad et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), effective, environmentally friendly(Ravi et al. 2025), and easily recyclable photocatalysts is extremely important(Liu et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Geopolymer, a new kind of three-dimensional inorganic polymer material, was first identified and named by French scientist Professor Davidovits in 1978(Davidovits \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Its raw materials are inexpensive and readily available, typically consisting of silicate salts like fly ash, gangue, slag, and metakaolin(Ambikakumari Sanalkumar et al. 2021, Xing et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). It is consists of a porous three-dimensional skeleton of aluminium-oxygen tetrahedra and silica-oxygen tetrahedra alternately connected with shared oxygen atoms.(Koč\u0026iacute; et al. 2022), which has excellent ion exchange(Clausi et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, Medri et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), stability(Han et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2024\u003c/span\u003e, Shumuye et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), and adsorption(Sarmento et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eBecause of their low cost(Ji et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), low CO\u003csub\u003e2\u003c/sub\u003e emission, low energy consumption(Ma et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), and environmental friendliness(Maiti et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), geopolymers have drawn a lot of attention recently in a variety of fields(Bai et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), including heavy metal fixation(Ji et al. 2019), adsorbent materials(Wei et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), membrane materials, photocatalytic materials(Dong et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), etc. In particular, geopolymers have been widely used as a new type of catalytic material in various catalytic reactions(Mu\u0026ntilde;oz et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). To overcome the drawbacks of traditional nano-polymers, which are prone to secondary pollution(Sarkar et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2020\u003c/span\u003e, Yan et al. 2023), have a low recycling rate, and are easily agglomerated, photocatalytic active factors are introduced into the geopolymer skeleton(Baig et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, Ranjbar et al. 2020), this will have a synergistic effect with the geopolymer, improving the photocatalyst's recycling rate, lowering reaction costs, and providing more active sites for the photocatalytic reaction(Barbarey et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2024\u003c/span\u003e, Botti et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFor loaded photocatalysts, more efficient separation of photogenerated carriers can be achieved by enhancing the electrical conductivity of the carrier so that the carrier has the role of transporting photogenerated electrons(Torralvo et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), allowing it to act as an electron acceptor and increasing the electron migration rate(Hasija et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Zainudin et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). By doping graphene, Zhang et al(Zhang et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). created conductive graphene-based geopolymer-loaded CuO composites for the first time. They discovered that graphene's exceptional charge-trapping capability can increase the conductivity of the geopolymer carrier, which in turn speeds up the separation of photogenerated electron-hole pairs and boosts photocatalytic activity. A new conductive carbon fiber/fly ash-based geopolymer composite was created and synthesized by Pan et al(He et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). It was discovered that the conductive carbon fibers were evenly embedded in the geopolymer matrix and that doping the carbon fibers increased the conductivity of the geopolymer to 8.44 S/m, 44,000 times higher than that of the geopolymer without the carbon fiber. Additionally, the carbon fibers were able to efficiently capture and transfer the photogenerated electrons in the photocatalytic reaction system, which could increase the separation rate of photogenerated electron-hole pairs and boost photocatalytic performance.\u003c/p\u003e\u003cp\u003eBecause each of the C atoms in carbon nanotubes (CNTs) has an unpaired electron in the P orbital, these carbon isotope isomers are arranged in cylindrical nanostructures and have exceptional electrical conductivity(Li \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Wang et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, Wieland et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Because of their high specific surface area and exceptional electrical conductivity(Phin et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), carbon nanotubes (CNTs) may quickly absorb photogenerated electrons from semiconductor photocatalysts in a photocatalyst system(Mateen et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), increasing the pace at which photogenerated light-generated carriers are separated(Amaya-Galv\u0026aacute;n et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2025\u003c/span\u003e, Wang et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2024\u003c/span\u003e, Zhang et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2018a\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eCNTs-modified geopolymer microspheres (GM\u003csub\u003eCNTs\u003c/sub\u003e) were prepared by doping CNTs into the geopolymer precursor, so that the microspheres would have the role of transporting electrons to improve the electron mobility. In this study, the Cu-La supported modified geopolymer photocatalyst (1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@\u003csub\u003eGMxwt%CNTs\u003c/sub\u003e) were prepared by constructing heterojunctions using ion-exchange properties of microspheres and van der Waals forces with La(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e as the La source and Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e as the Cu source. The degradation of 50 mL of TCH solution at a concentration of 30 mg/L, catalyzed by visible light, was used to assess the photocatalytic activity.\u003c/p\u003e"},{"header":"2. Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Materials\u003c/h2\u003e\n \u003cp\u003eMetakaolin: (Guangzhou Changyu Chemical Co., Ltd, model 1305, white powder) The chemical composition of metakaolin was analyzed by X-ray fluorescence characterization. Its chemical composition is mainly SiO\u003csub\u003e2\u003c/sub\u003e, Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, CaO, and Na\u003csub\u003e2\u003c/sub\u003eO, and contains traces of MgO, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, K\u003csub\u003e2\u003c/sub\u003eO, etc.\u003c/p\u003e\n \u003cp\u003eAlkali exciter: (Jiashan Yourui Refractories Co., Ltd.) water glass (liquid sodium silicate) with an initial modulus of 3.26, which is adjusted to 1.2 by adding NaOH and deionized water.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Preparation of GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e\u003c/h2\u003e\n \u003cp\u003eCNTs modified geopolymer microspheres (GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e) were prepared by using suspension-dispersion technique using metakaolin and alkali exciters as precursors by doping CNTs into the precursors in the following experimental steps: A certain mass of CNTs was doped into the metakaolin and stirred to make a homogeneous mixture, and then 8.5 g of alkali exciter was added into the precursor and stirred for 15 min to make a full reaction to form a geopolymer slurry. The slurry was slowly dripped into hot dimethicone oil (80\u0026deg;C) at a stirring speed of 800 r/min and stirred for 10 min, and the slurry was subjected to shear force in the stirred hot silicone oil, and microspheres were formed through suspension-dispersion. Then the beaker containing microspheres and dimethicone oil was moved to an 80\u0026deg;C oven to fully cure and maintain for 24h, and then filtered to separate the GM\u003csub\u003ex wt% CNTs\u003c/sub\u003e, washed with cyclohexane several times to fully remove the silicone oil on the surface of microspheres, and then moved to a 70\u0026deg;C oven to dry for 12h, and then calcinated by a tube furnace at 500\u0026deg;C for 2h (argon atmosphere). Then wash with deionized water several times to fully wash away the NaOH on the surface of the microspheres, and then put into the oven at 60\u0026deg;C to dry for 12h. Finally, the microspheres were sieved with 100 and 300 mesh sieves to obtain 100\u0026thinsp;~\u0026thinsp;300 mesh GM\u003csub\u003eCNTs\u003c/sub\u003e, respectively.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Preparation of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/h2\u003e\n \u003cp\u003eUsing GM\u003csub\u003eCNTs\u003c/sub\u003e as carriers, a certain amount of Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e was weighed and dissolved in 20 mL of deionized water and sonicated for 15 min, and then 0.5 g of 7.5% La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM was added to the Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e solution, which was stirred for 6 h at room temperature, and Cu\u003csup\u003e2+\u003c/sup\u003e was loaded onto the 7.5% La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM by using the ion-exchange properties of the microspheres and the effect of van der Waals\u0026apos; force on its surface. Then the Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e loaded photocatalytic composite of 7.5% La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM (Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/7.5% La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM) was obtained by evaporation with stirring in a water bath at 80\u0026deg;C. Finally, the Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/7.5% La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM was moved to a muffle furnace and calcined at 500\u0026deg;C for 5 h to obtain the geopolymer-loaded Cu-La bimetallic photocatalytic composites 1.0% CuO/7.5% La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt% CNTs\u003c/sub\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Characterization analysis\u003c/h2\u003e\n \u003cp\u003eX-ray diffraction (XRD): characterizing the crystal structure of the catalyst; Low-temperature nitrogen adsorption-desorption isothermal curve (BET): testing the specific surface area and other information of the catalyst; X-ray photoelectron spectroscopy (XPS): testing the surface element composition, valence and other information of the catalyst; Scanning electron microscopy (SEM): characterizing the surface morphology of the catalyst; Transmission electron microscopy (TEM): characterizing the microscopic morphology, particle size and distribution of catalysts; UV-vis diffuse reflectance spectroscopy (UV-vis DRS): testing the wavelength range of light absorbed by the catalyst and additional information; Photoluminescence spectroscopy (PL): characterizing the photogenerated electron-hole recombination rate of the catalyst; Infrared spectroscopy (FT-IR): analyzing the characteristic functional groups of catalysts and other information.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5 Photocatalytic activity\u003c/h2\u003e\n \u003cp\u003eTo assess the photocatalytic activity of the samples, the photocatalytic degradation of TCH solution was selected in this paper. To do this, 50 mL of a specific concentration of TCH (30 mg/L) solution was pipetted precisely using a measuring cylinder and then added to the photocatalytic reaction device. Next, 0.1 g of photocatalyst was weighed into the photocatalytic device that was equipped with the TCH solution, and simultaneously, the electronic stirrer was activated. Photocatalysis starts with 30 min of light avoidance to bring the reaction to adsorption-desorption equilibrium, and then a xenon lamp is switched on at the end of the dark adsorption, while condensate is passed through. Then 8 mL of reaction solution was taken in a 10 mL centrifuge tube every 20 min, and the supernatant was taken in a 10 mm cuvette by centrifugation at 4000 r/min, and the absorbance (A\u003csub\u003et\u003c/sub\u003e) of the photocatalytic reaction solution was measured at the moment t at the wavelength of maximum absorption of the TCH (\u0026lambda;\u0026thinsp;=\u0026thinsp;357 nm), using a visible spectrophotometer. The degradation rate of the TCH solution was calculated by Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The proposed first-order kinetic constants of the photocatalytic reaction were calculated from Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u003cimg src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAARQAAABmCAYAAAAK7W4HAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAAFiUAABYlAUlSJPAAABQHSURBVHhe7dz/a9vG/wfwpz+/l03xfioljMi/jBYCm1tGSQsNrMqyMhh0k1n3Q6DQVlkpvNe1CU7KGN1GnX4ZlC6xSwNhsMopgf6UbE6hP8ymsNYbNm3ZL5Ep/SE/STPb/oD7/DCfkM6SLNty6javB/gH35315SS9dHc6OcYYYyCEkAj8n5hACCGdooBCCIkMBRRCSGQooBBCIkMBhRASGQoohJDIUEAhhESGAgohJDIUUAghkaGAQgiJDAUUQkhkKKAQQiJDAYUQEhkKKISQyFBAIYREhgIKISQyFFAIIZGhgEIIicwrHVDm5uYQi8Vcn1KpJBYDAFSrVaRSKczMzIhZr4RcLoexsTHf/Q9rZmYGsVgMtVpNzIpcO8ePhFcqlZDL5cTkQLVaDXNzc7AsS8xyY6+wTCbDALBisShmuWQyGSZJEtN1XcxqYpomU1VVTN4ymUym5f74KRaLTJZlpmmamBWKaZpMkqRQv1dVlZmmKSZ3LOyxbIeu60yW5cBlmqbJ0uk0kySJAWCapvnuV9iyuq63LMMZhsEURRGTO6bruu95bhgG0zTNd3383K9UKmKWbdsHFH4CBFWSU5hl9gq/oP0OeBimabJkMhkqKIiy2SwD0LKuisUiA8AymYyY1bEo671SqTBN0xiAwGXyukomk8wwDPuCSiaTTUEgbNnV1VV7nYZhMEmSWDqddi3LKZlMtqzvsHRd970ZZrNZJssyAxB4flUqFSZJUtP+c9s6oPAT3y9ie+GV3skF2S1d1+2LwDAMMTu0SqXCALBsNitmBZJlOfBk4/jFKsuymNWxVseyE3w7/ZbJ1+msa8MwGICmIBC2rKIoLJlM2t/5NnjJZDJtHyM//JgHnTd8e1sd40wm41vGe09eEa1OQkVR2jrpdV1nyWQykou6E7Is2+vvNqBpmhZ4pxHxYNYq+PK7Lg+8rcqH5XcsM5mM7zpM0wysJ79lMkdr0Hnxc4qiMAB23bVTVrxg/bahWCz6XrSdUBTFt3XiJG6fFx54vOo90kFZPoi2d+9eWJYFy7IwOTmJWCyGgYEB5PN58ScvTLVaRaFQwLlz58QsX1evXsX3338PVVUBACsrK2KRnllbW0MikcCtW7cAAPl8vvUAWYAjR46gXq+H3oelpSXIsoxUKiVmuSwuLmJ6etqu16WlJbFIpI4fP46rV682nVuWZWFsbAwHDx50pYf122+/oV6vQ5ZlMQujo6MAgHv37gFtlg3Dsiz873//w08//SRmdaRUKqFQKODQoUNiVkeGhoYgyzKuXr0qZkX3lKdWq2FwcBDZbBblchnXrl3DhQsXcPDgQayurmJgYACTk5NdXQRRunPnDgBg9+7dYpanUqmEer2OkZERnD59GgBw6dIlsVjPXL9+HRMTExgeHoaiKG0FAy/j4+MAgLt374pZTcIGX8uysLCwgKNHj+Lo0aOQJAmFQgHValUsGpl4PI5ffvnFFVR4MDl79mzLAOjnyZMnAIC3335bzLI9fvwYaLOsoiiua+DZs2cAgLfeestOu3DhAr7++mvE43E7rRu3b98G2jjXw0gkEiiXy01P+yILKJubm0ilUvZGr6+v4+LFi0ilUhgfH8eJEydQr9fx559/ij+1lUqlpseEQZ9uHiH+/vvvAICRkRExy9ONGzfwzTffAI3fyLKMer3edGfshWq1io2NDfvimJiYAABcvnxZKNmeZDKJQqEgJjfJ5XKQJAlHjx4Vs1xWVlaQSqUwNDSEeDxub2+7jyjb5Qwq/PF4N8EEAO7fvy8mNeHnUDtlz5w5g3K5jFKphFqthnw+D03T7OCxtrYGSZLsgB+FR48eAULQ6pZfyyuygCJemB9//LErwu7fvx8A8ODBA0cpt5GRETTGdUJ9xHW2o1AoQJIkMdlTrVbD+vq66wTlwcWr2Re1XC7nah2kUinIsgzDMLC2tuYq2w5+fMS7jFOtVsPCwoLrpPdz+fJlnDx50v7+5ZdfAgAWFhZ63jKNx+NYXl7GqVOnsHfv3q6CSS+Nj48jm83iww8/tLuQFy9eBBp1/dVXX+GLL74AGi2tVCqFWCyGRCLR8bEul8uA43hH6e+//3Z9jyygvIz27dsnJnm6cuUKpqenXWmpVAqSJNl3m17hdzGxdcADzPXr113pndjc3BSTbLxbdfz4cTHLJZ/PI5FIYHh42E4bGhqyx5sWFxcdpaNnWRZUVUU2m8WjR4+2pOXYqZMnT+Kvv/4CYwzz8/P2hT45OYlbt27Z348dO4ZyuQzTNHHu3Dl88MEHgcH/RRBbZ30VULayyxOWZVnI5/OYmppqWn+9Xgca3SEvzpme4rb67atYbmVlBfV6HW+88Yar3KlTp4BGS6tXYxSWZeHSpUtQVRVDQ0NitsvS0hIKhULT/iwvLwMB403OepibmxOzQ3GOmZw8ebJpTKUTvEkfhJdpp6yfubk5jI6O2gG5VquhUCjgxIkTiMfjdsvvypUrwi/7S18FlK3s8oS1uLiIVCrVtG7GGIrFIgBgeXm56c6Rz+dx8+ZNu+yBAwdcZXbs2AFFUZo+O3bssMvwC9owjKZ1M8agKArgM0YxNjYmJrXt3r17qNfr9iC0n1KphI2NjabtY4zBNE1IkuQ53lSr1XDgwAF7/+7fv99UphWvAVivgdp2DQ4OAh5NejgGUnmZdsp6qVaruH//Ps6fP2+n8Vbjnj17HCWDu6cvQlOgFJ8jd4tPFhNnSfql95LfM37G/nveHmb3W03N5vMMxIlOsiy7ntNnMpnAORFedF0PnBPA69Q5z8GZ3grfdr/5NHzeSyuapgUeV34cxGVpmuaqk2Lj1QAvfseyl/NQvLaZNWavOuu8nbIi0zSZoihNx4AfQ+e2IcQcES98G8R1eAm7Dl534sS7vmqhbCV+dw/CxwWCWkJnzpwBhIHHWq0GwzBcYzSDg4NYX1+3v4cxOzuL2dlZMdk2MjKCZDIJOMYo8vk8Dhw4AAAtuxF8e726M2trazAMA2fPnhWzXPgYT9AYC88Tx5vW19dd80R27twJwzDaugufP3/edwA2Ho9jfn5eTA4lHo8jnU43PRqt1Wool8tIp9P2WEc7ZUXXrl3DxMRE0zHYuXMn4PEQQywXxuHDh4EWY2Xt+uOPPwAA7777rit92waUd955B2g0172USiVMTk7i9ddfD3xC8c8//wAA6vU6Pv/8c9RqNfvAOQ/+rl27YBiG/T2I1ZgQ2Kq8c7umpqawtraGVCoFXdeB/5oorma0k2VZKJfLvoH1+vXrkCTJ92JF44JRVRUDAwOezX3OmTcxMWGP+RiGgV27dtl5vL6iPPH9WJZlDyiKFy33xRdfIJlMQlVVWJZl728ymbSfxHRSluNB26uOh4aGoCgKbt68Ccuy7G7tp59+KhZt6ZNPPgEAPH36VMxy4U+RNjY2WgZ1wzCQTCZdg/BAmHZxm/y6Nn7pvRTUpOXbI3ZVnHnOj9cy+PLFzw8//MDEqg3bDWGOrgj/+DVBxfXysnyafBD+kprYZGWOqdWtjpW4bq/yXnXJy8KjXr3SWItj2S6/4+aFd5sA2C/yBXVf2ikrvjgoci5PlmW2uroqFgmt1dR7sS74MfISNPXeuxZ7oN8CCmuMEfj12bvBK9zZZ9Ubr8pvhTABRVVV33d5+EnslRclcZzJq964VseSBAvzcmBYmYCXA7dtlweNR52GYXg+JekGf9fB2XR//vy53Zd90UqlEpaXlzE9Pd3Ut7ca0+fDTGTr1uHDh/H8+XP7++bmJmRZ7micgAQbHh6GrutIp9NiVlssy8LNmzf93zMSI0yv9GMLhXXwfyhhOZ/QBN15e8HZvRLr2zRNJsuyb/OX19lWbCuvF05ssTiFOZakNV3XA598BTH76Q+W+jWgsEY5SZI8xxO64eyrt9qGqPH1OgNDsVhkUuMf1/y6M93+gVO7nGMsQedG2GNJWisWi76B249hGCybzfqeN9yWBRR+N/K7M/aC84JudWEXi0WmqqrnIO2rIJvNMkVRfPe/H7Vz/Eh/iLH/7maEENK1bT0oSwiJFgUUQkhkKKAQQiJDAYUQEhkKKISQyFBAIYREhgIKISQyFFAIIZGhgEIIiQwFFEJIZCigEEIiQwGFEBIZCiiEkMhQQCGERIYCCiEkMhRQCCGRoYBCCIkMBRRCSGQooBBCIkMBhRASGQoohJDIUEAhhESGAgohJDIUUAghkaGAQgiJDAUUQkhkKKAQQiJDAYUQEhkKKISQyFBAIYREhgIKISQyFFAIIZGhgEIIiQwFFEJIZLZtQLEsC7lcDolEAqVSScx+qZRKJUxOTmJsbEzM6kq1WkUqlcLMzIyY1XMzMzOIxWKo1WpiVqRyuRzGxsZ6eg6USiXkcjkxOVAnv+kLbJvKZrMsmUwyAKxYLIrZL41KpcLS6TQDwBRFEbM7lslkmCRJTNd1MYsxxlixWGSqqjJJkhgAe/26rjPTNJmmaeJPQjNNk0mSFLgMXdeZoij2uiVJYqqqsmKxyCqVCstkMuJPfBWLRSbLcuD6OqXrelMd8vrhdSfLMstms64yrHFsVVVlpmmKWX1r2wYU1rhoXvaAwkUZUNLpNJMkiVUqFTGLmaZpX8iaprnKrK6u2nndbEs2m2UAPNdfqVSYLMtMkiSWyWSYYRiMNbZL13UmyzID0FZAYY3fJ5PJSIOKrutMVVVXGl+PJElMURR7e3l9irLZbFd1udUooFBAcSkWiwxA012VOS4Gv3xO0zSGLhq/six77kulUmGSJPkGO+bYRq/ft1KpVBgAz9ZCu/iyeMDjstks0zTN1ergAdQviCqK0naAfFE6P+qvAAoozfhd0wvvWnndSUV+y2hF13XfgBUmmDHGmGEYHdcF74p0281QFKWpdcIa55wXHoS98nmdiMGpH23bQVk/sVjM9ZmbmxOLvBTEQedqtYqxsTHEYjEkEglUq1XxJ6hWqygUCjh37pyYBcuy8N133wEATp48KWY38VpGGEtLS5BlGalUypW+traGcrkMSZKa8kRDQ0P46KOPxORQjhw5gnq9jpWVFTErtFKphEKhgEOHDolZOH/+vJgEAHjzzTcBAK+99pqYhX379gEAFhcXxay+QwFFsLq6CgDIZDIwTdP3BOh3KysruHXrFgzDwNOnT5HL5TA7O4tsNgvDMDA1NSX+BHfu3AEA7N69W8xyXWDDw8OuPC9hgo4oKKD9+OOPgOPiaqWT9QPA+Pg4AODu3btiVmi3b98GfOqxlffee09MwtDQEABgeXlZzOo/YpNlOxG7PHzA0asfGwYffwj7ibKrBY8uD9+/dDrtSucDpyK/dOZokovriFJQd6PTwdZO8K5Vp/jvvfbDj6ZpgXXLj02n5+ZWoRZKQ7VaxbFjx5DJZELdgb2MjIygMS4V6jMyMiIuoifef/99MQloNM2dCoUCJElypXG9ng9Sq9WwsLAATdMQj8fFbBiGISb1DF9/p/tcLpcBx3JaqdVqyOfzmJ+fF7Oa/Pvvv2JSX6GAAuDnn3/GoUOHcObMmY6DyasibJciarxLdfz4cTHrhdnc3BSTeiKdTmN+ft7u2gR58OCBmNRXKKAAGBwcBAB89tlnHd+V0Ljji4O6QR+xheAklo294AHi0dFRAMDGxoaY1TXLsnDp0iWoqup7USmKAgB49uyZmBUKr8OoZxN3K5/PY2BgoOVA88uCAkpj8Gx+fh71eh2qqorZAIDJycmWwSbKLo+iKE0fHvheBH5BG4bRsh5EpVIpMBjeu3cP9Xodp0+fFrNs/KnN+vq6mNVSIpGArutgjGF0dBSTk5NikReiWq3i8ePHobo63P79+8Wk/iIOqmwn4qAsH3gU51kYhsHQ5/MAvAZMxf3j+ACfmI7GYLEf/juxfrysrq7aA4itJmbJssySyaSY7MKn4yPEPBTmmO/BZ886tTqWfD+DygThg7JBv+evTIRFg7Ivofn5eSSTSSwsLCCfzwONu6ssywAAWZb75u7WC7wV4ieTyUCSJFf9eKlWq3jy5AmGh4eRSCRQKBQwNTWFWCwmFsXa2hoMw8DZs2fFLJd4PG7fyScnJz3n0XD5fB579uwBAPz66684fPiwK1+WZTx8+NCV5mRZFuB4XNsuvj6/MZhqtYqpqSl8++23YhZyuZznvj18+BCSJPX/GJ8YYbYTVVWb7rjOR798CjZPC7rjvEh8mre4jXz/nHdC0zTtR7DiFHM+E1ZsuTjx6e+83pxlDcNgmUymqQUjy7JvC0VRFCZJkpjsi88a5e/yOO/YlcbLdM4WjFfryCuNM02TwaO1146gKfy8/vjrAc6PX0uNb1M7LZoXZdsGFH4BOj9+6f0cUHi3xvnxSnPuh/PjvHB4fqsT1zRN+6U1vhzn274iv4DCu5JeeUEMw2DpdNruWqDxxq6maU3HyCt4eKVxq6urDD7BoB2Kx9R7wzDsYOz38VrvyzT1ftsGlHb0c0CJmizLTWMO3fILKHzMqp0JYO3SNM2zxeQ3DsP/kqHbbfJ7ObATQQGw39AYCnFZWlqCYRg9/3Mfy7ICJ7JF5eDBg01PpQzD8JxvUyqVsLy8jOnp6a63aXh4GLquI51Oi1lt4VMLXppXQMQIQ5o5n/K8LHeKbgT9H0on+B1W13X7js27ZVHcwVuRZdn1JE9ssTDH2JLYTemWruue6wuDjwl121raShRQQuIDmV5jBK+iTOMf27z69O3iwcN5YfE/GNoqfIzCa53FYpFJjX+I68XFWywWfbtYfiqVSiR1v9Vi7L/KJqRJqVTCjRs3IMuy5yPOV0Eul8Pdu3cxOzsbONGQhEMBhRASGRqUJYREhgIKISQyFFAIIZGhgEIIiQwFFEJIZP4f1VPn9WwjzKkAAAAASUVORK5CYII=\"\u003e\u003c/p\u003e\n \u003cp\u003eWhere \u0026eta; is the degradation rate of the TCH solution, A\u003csub\u003e0\u003c/sub\u003e is the initial absorbance of the TCH solution, A\u003csub\u003et\u003c/sub\u003e is the absorbance of the TCH solution at time t, k is kinetic constant (min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), C\u003csub\u003et\u003c/sub\u003e is the concentration of TCH solution at time t, and C\u003csub\u003e0\u003c/sub\u003e is the concentration of TCH solution at the initial time.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003ch2\u003e3.1 Microscope analysis\u003c/h2\u003e\n\u003cp\u003eThe SEM images of the catalysts 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e are shown in Fig.1(a) and Fig.1(b). Both materials showed high sphericity, dense and compact microsphere structures, and rough surfaces containing a large number of pore structures. However, by comparison, it was found that the surface roughness of the geopolymer microspheres doped with CNTs was larger and contained more pore structures, suggesting that the doping of CNTs could improve the morphological structure of the microspheres and give the material a larger specific surface area, which could provide richer active sites for the photocatalytic reaction. Figure 1(c) shows the elemental mapping of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e. The C, Cu, and La elements are uniformly dispersed, which indicates that CNTs, Cu, and La elements are highly dispersed in the microspheres.\u003c/p\u003e\n\u003cp\u003eThe distribution of grains on the surface of the photocatalytic microspheres and the crystal spacing were analyzed by TEM characterization to determine the presence of CuO and La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e and their distribution. As shown in Fig. 2(a), the microsphere surface was loaded with a large number of grains with uniform distribution, indicating that CuO and La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u0026nbsp;\u003c/sub\u003ewere uniformly dispersed on the microsphere surface. The crystallographic spacing of the corresponding grains in the two selected regions in Fig. 2(b) are 0.311 nm and 0.273 nm, respectively, with 0.311 nm attributed to the {101} crystallographic plane of La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003csub\u003e(Huang et al. 2019)\u003c/sub\u003e, and 0.273 nm attributed to the {110} crystallographic plane of CuO(Zhang et al. 2018b), which confirms the presence of CuO and La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e on the surface of the microspheres with a homogeneous distribution, and suggests that 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e photocatalytic composites have been successfully prepared.\u003c/p\u003e\n\u003ch2\u003e3.2 EDS analysis\u003c/h2\u003e\n\u003cp\u003eTo determine the elemental composition of the photocatalytic microsphere surface, the EDS energy spectrum of\u0026nbsp;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e was tested. As shown in Fig. 3, the binding energies of 0.28 KeV, 0.52 KeV, 1.04 KeV, 1.48 KeV, 1.74 KeV, 2.14 KeV, 4.64 KeV, and 8.04 KeV corresponded to the elements C, O, Na, Al, Si, Au, La, and Cu, where the detection of elemental Au is attributed to the surface gold spraying of sample 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e (since non-conductive samples need to be surface sprayed to be tested), O, Na, Al and Si elements attributed to the solid inclusion in the geopolymer precursor biotite kaolinite, Cu and La elements are attributed to CuO and La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, and C is attributed to CNTs, and combined with other characterization analyses, O also corresponds to the O element in CuO and La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e\n\u003ch2\u003e3.3 BET analysis\u003c/h2\u003e\n\u003cp\u003eThe low-temperature N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption curves of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and\u0026nbsp;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e are shown in Fig. 4(a), and the adsorption curves of the two materials increase slowly within the low-pressure section P/P\u003csub\u003e0\u003c/sub\u003e=0.025~0.85, which indicates that the amount of nitrogen adsorbed in the low-pressure stage is gradually increasing, and the adsorption curves rise steeply in the section P/P\u003csub\u003e0\u003c/sub\u003e=0.85 ~ 0.98, and the isothermal adsorption curve and the desorption curves in this stage form a typical H3 type hysteresis loop, which indicates the existence of a large number of mesopores in the geopolymer microspheres. According to the classification criteria of the standard isotherms for physical adsorption, the adsorption-desorption isothermal curves of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and\u0026nbsp;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e belonged to the isotherms of class IV, and there was no significant change in the adsorption-desorption isothermal curves of the two materials. Fig. 4(b) shows the pore size distribution curves of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and\u0026nbsp;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e. As shown, the pore size distribution of the two samples is in the range of 12 ~ 70 nm, which also indicates that a large number of mesopores exist in 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and\u0026nbsp;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e. These pores, on the one hand, can allow the microspheres to have a large specific surface area and provide abundant active sites for this photocatalytic system, and on the other hand, they can reduce the mass-transfer resistance during the reaction process, so that the photocatalytic reactants and reaction products to pass through these pores quickly.\u003c/p\u003e\n\u003cp\u003eTable 1 shows the specific surface area, pore volume, and pore size data of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and\u0026nbsp;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e. As shown in Table 1, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM has a specific surface area of 35.70 m\u003csup\u003e2\u003c/sup\u003e⸱g\u003csup\u003e-1\u003c/sup\u003e, a pore volume of 0.19 cm\u003csup\u003e3\u003c/sup\u003e⸱g\u003csup\u003e-1\u003c/sup\u003e and pore size of 18.00 nm, whereas 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e has a specific surface area of 41.41 m\u003csup\u003e2\u003c/sup\u003e⸱g\u003csup\u003e-1\u003c/sup\u003e, a pore volume of 0.21 cm\u003csup\u003e3\u003c/sup\u003e⸱g\u003csup\u003e-1\u003c/sup\u003e and a pore size of 33.09 nm. The pore diameter of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e is bigger than those of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, which shows that the morphological structure of microspheres can be improved by doping CNTs, which gives them a larger specific surface area and can provide more active sites for the photocatalytic reaction system.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eSpecific surface area, pore volume, and pore size of\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"99%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 39.3939%;\"\u003e\n \u003cp\u003ecatalyst\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 16.1616%;\"\u003e\n \u003cp\u003eBET(m\u003csup\u003e2\u003c/sup\u003e⸱g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.2727%;\"\u003e\n \u003cp\u003epore volume(cm\u003csup\u003e3\u003c/sup\u003e⸱g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17.1717%;\"\u003e\n \u003cp\u003epore size(nm)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 39.3939%;\"\u003e\n \u003cp\u003e1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.1616%;\"\u003e\n \u003cp\u003e35.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27.2727%;\"\u003e\n \u003cp\u003e0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17.1717%;\"\u003e\n \u003cp\u003e18.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 39.3939%;\"\u003e\n \u003cp\u003e1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16.1616%;\"\u003e\n \u003cp\u003e41.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 27.2727%;\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 17.1717%;\"\u003e\n \u003cp\u003e33.09\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e3.4 XPS analysis\u003c/h2\u003e\n\u003cp\u003eFig. 5 shows the XPS spectra of GM、1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e. The elemental composition of the samples as well as the chemical valence states were analyzed. Figure 5(a) shows the total spectra of the three materials at binding energies of 74.0 eV, 102.0 eV, 531.0 eV, 835.0 eV, 934.0 eV, and 1072.0 eV corresponding to the elements of Al, Si, O, La, Cu, and Na in sample 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e.\u0026nbsp;Fig. 5(b) shows the high-resolution spectrum of La 3d for 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e. There are more obvious spin-orbit splitting peaks in the high-resolution spectrum of La 3d, and the splitting peaks of each spin-orbit splitting peaks multiply and cleave into two splitting peaks, which corresponds to La 3d 5/2 and La 3d 3/2 in La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e at the binding energies of 835.0 eV/838.5 eV and 851.9 eV/855.5 eV. Fig. 5(c) shows the Cu 2p high-resolution spectrum of c. The binding energies 933.2 eV and 953.2 eV correspond to Cu 2p 3/2 and Cu 2p 1/2, respectively, with a peak spacing of 19.9 eV and accompanied by two satellite peaks, which suggests the presence of Cu\u003csup\u003e2+\u003c/sup\u003e in the form of CuO(Li et al. 2023). Therefore, XPS analysis confirmed the presence of La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and CuO in the samples, indicating that the 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e photocatalytic composites were successfully prepared.\u003c/p\u003e\n\u003ch2\u003e3.5 UV\u0026ndash;vis DRS analysis\u003c/h2\u003e\n\u003cp\u003eThe response properties of photocatalytic materials GM, 7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e to light were investigated by UV-Vis DRS characterization. As shown in Fig. 6 (a), all four samples showed strong light absorption in the UV region, with 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e having stronger light absorption properties than 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM in the visible region (400 ~ 800 nm).\u0026nbsp;It can be seen that by doping CNTs into the geopolymer microspheres, the visible light absorption range of the catalyst can be significantly increased, making it more photoresponsive to the visible region, reducing the energy needed for electron migration and achieving the enhancement of its photocatalytic activity. Fig. 6 (b) shows the forbidden bandwidth of the catalyst calculated by Tauc\u0026apos;s equation (Eq. 3), and the forbidden bandwidth of the semiconductor is obtained by linear extrapolation from Eq. Eg = 1240/\u003cem\u003e\u0026lambda;g\u003c/em\u003e. As shown in Fig. 6 (b), the forbidden bandwidths of GM, 7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e are calculated by linear extrapolation to be 3.28eV, 3.22eV, 1.80eV, 0.39eV, respectively. Therefore, the doping of CNTs in microspheres resulted in a certain magnitude reduction in the forbidden band width of catalyst 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e, which allowed it to be excited by longer wavelengths and had a stronger photoresponsivity, achieving the effect of improving its photocatalytic performance.\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\"\u003e\u003c/p\u003e\n\u003cp\u003eWhere \u003cem\u003e\u0026alpha;\u003c/em\u003e denotes the absorption coefficient, \u003cem\u003eh\u0026nbsp;\u003c/em\u003edenotes Planck\u0026apos;s constant (1.6 \u0026times; 10\u003csup\u003e\u0026minus;19\u003c/sup\u003e), \u003cem\u003ev\u003c/em\u003e denotes the optical frequency (Hz), A denotes the proportionality constant; E\u003csub\u003egap\u0026nbsp;\u003c/sub\u003edenotes the band gap width of the photocatalyst (eV).\u003c/p\u003e\n\u003ch2\u003e3.6 PL analysis\u003c/h2\u003e\n\u003cp\u003eThe PL spectra of GM, 7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e were tested at an excitation wavelength of 250 nm, as shown in Fig. 7. The PL spectra of the photocatalytic materials were tested to investigate the separation of photogenerated carriers of the catalysts. The order of peak intensities in the PL spectra of the four materials is GM \u0026gt; 7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM \u0026gt; 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM \u0026gt; 1.0%CuO/7.5%La2O3@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e.\u0026nbsp;Among them, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e exhibit the weakest fluorescence intensity compared to the other three materials, which is attributed to the fact that the doping of CNTs in the geopolymer precursor increases the conductivity of the material and enhances the photogenerated carrier mobility rate to achieve the enhancement of the photocatalytic effect of the material.\u003c/p\u003e\n\u003ch2\u003e3.7 EIS analysis\u003c/h2\u003e\n\u003cp\u003eElectrochemical impedance spectroscopy (EIS) responds to the charge transfer ability at the interface of photocatalytic materials. The smaller the arc radius of the EIS spectrum, the higher the conductivity and the lower the resistance of charge transfer at the interface of the sample, i.e., the higher the efficiency of photogenerated electron-hole separation. Therefore, to investigate the effect of CNTs doping on the conductivity of photocatalytic materials, the EIS spectra of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e were characterized and analyzed. As shown in Fig. 8, the radius of arc of Nyquist curve of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e is smaller than that of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM, i.e., the conductivity of\u0026nbsp;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e is lower than that of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM.\u003c/p\u003e"},{"header":"4. Evaluation of photocatalytic performance","content":"\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Photocatalytic degradation of TCH\u003c/h2\u003e\u003cp\u003eThe photocatalytic degradation performance of the four materials was analyzed by photocatalytic degradation of 50 mL of TCH solution at a concentration of 30 mg/L. The comparative photocatalytic performance plots of GM, nano-TiO\u003csub\u003e2\u003c/sub\u003e, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e and the fitted plots of the proposed first-order kinetic constants for the degradation of TCH were tested, respectively, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a) and (b). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a), the strong and weak photocatalytic performances of the four photocatalytic materials for degrading TCH solution were in the order 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e \u0026gt;1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u0026thinsp;\u0026gt;\u0026thinsp;nano-TiO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;GM, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e had the highest photocatalytic activity for degrading TCH solution, and the degradation rate of 50 mL of TCH solution with concentration of 30 mg/L could reach 89.51% when the reaction was carried out for 100 min. The adsorption rate of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e on TCH was 37.45% after 130 min of dark reaction, and the adsorption-desorption equilibrium was reached after 30 min of dark reaction. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e9\u003c/span\u003e (b) shows the fitted results of the proposed primary kinetic constants for the degradation of TCH solution by the four catalysts, with the proposed primary kinetic constants of 0.00316 min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 0.00772 min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 0.01512 min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 0.01893 min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for GM, nano-TiO\u003csub\u003e2\u003c/sub\u003e, 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e, the proposed first-order kinetic constants of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e were the largest indicating the fastest degradation rate to TCH solution and the proposed first-order kinetic constants were 1.25 times higher than that of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Effect of CNTs doping on the photocatalytic performance of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e\u003c/h2\u003e\u003cp\u003eTo investigate the optimal doping amount of CNTs, a total of 1.0% CuO/7.5% La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt% CNTs\u003c/sub\u003e were tested for photocatalytic degradation of TCH at doping amounts of 0.1 wt%, 0.3 wt%, 0.5 wt% and 0.7 wt%, respectively. The experimental results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e10\u003c/span\u003e (a) of The photocatalytic activity of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e was highest when the CNTs were doped at 0.5 wt%, and the degradation rate of TCH solution was 89.51% when the photocatalytic reaction lasted for 100 min. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e10\u003c/span\u003e(b) shows the fitted plot of the proposed first-order kinetic constants for 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt% CNTs\u003c/sub\u003e photocatalytic degradation of TCH, and the proposed first-order kinetic constants for 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5% CNTs\u003c/sub\u003e degradation of TCH were the largest when the doping amount of CNTs was 0.5 wt%. Therefore, the experimental results showed that the optimum doping amount of CNTs was 0.5 wt%.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe effect of coexisting anions Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e, NO\u003csup\u003e3\u0026minus;\u003c/sup\u003e, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e, SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, and CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e on the photocatalytic activity was investigated by adding 1 mmol of NaCl, NaNO\u003csub\u003e3\u003c/sub\u003e, Na\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, and Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, respectively, to the TCH solution. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e11\u003c/span\u003e, the photocatalytic activity of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e was enhanced when PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e and CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e were present in this system, which was attributed to the fact that the PO\u003csub\u003e4\u003c/sub\u003e \u003csup\u003e3\u0026minus;\u003c/sup\u003e and CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e made the TCH solution alkaline, which favored the production of more \u0026bull;OH under alkaline conditions and enhanced the photocatalytic performance of the system. However, these co-existing anions had little effect on the system, and therefore\u003c/p\u003e\u003cp\u003ethe 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e showed good salt resistance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\u003ch2\u003e4.4 Evaluation of Recycling Stability\u003c/h2\u003e\u003cp\u003eTo investigate the stability and recyclability of the photocatalytic material 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e, the stability of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e was investigated by centrifuging, washing and vacuum drying the samples at the end of the photocatalytic reaction and repeating the photocatalytic performance evaluation experiment under the same experimental conditions. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e12\u003c/span\u003e, the degradation rate of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e on TCH solution can still reach 72.35% after 4 photocatalytic recycling, and it exhibits good stability. However, the degradation rate of the material to the TCH solution decreased somewhat after 4 cycles, which may be due to some loss of the catalyst in the process of recycling, or since the fact that some of the undegraded TCH molecules adsorbed on the surface of the microspheres in the photocatalytic reaction remained on the surface of the catalyst after recycling, which led to the decrease of the active sites of the catalyst.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\u003ch2\u003e4.5 Universal Performance Evaluation\u003c/h2\u003e\u003cp\u003eThe practical application value of photocatalyst 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e was explored by evaluating the photocatalytic performance of the photocatalytic materials for different organic pollutants. The photocatalytic degradation performance of the photocatalytic materials was investigated for TCH, MB, MR, and MG, respectively, according to the photocatalytic performance evaluation method in Section \u003cspan refid=\"Sec7\" class=\"InternalRef\"\u003e2.5\u003c/span\u003e. The experimental results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e13\u003c/span\u003e. The degradation rates of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e on TCH, MB, MR and MG were 89.51%, 94.86%, 88.27% and 92.24%, and the photocatalytic material 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e showed good photocatalytic degradation of these four organic pollutants, which indicates that the material has excellent universality and has certain application value.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\u003ch2\u003e4.6 Active Species Detection Experiment\u003c/h2\u003e\u003cp\u003eTo investigate the catalytic mechanism of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e photocatalytic degradation of TCH, IPA, EDTA-2Na, and ASA were added as \u0026bull;OH, h\u003csup\u003e+\u003c/sup\u003e, and \u0026bull;O\u003csup\u003e2\u0026minus;\u003c/sup\u003e radical trapping agents, respectively, to the system degrading TCH solution. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e14\u003c/span\u003e, the photocatalytic degradation of TCH solution did not decrease significantly when the \u0026bull;OH radical capture agent IPA was added to the photocatalytic reaction system, but when the h\u003csup\u003e+\u003c/sup\u003e and \u0026bull;O\u003csup\u003e2\u0026minus;\u003c/sup\u003e radical capture agents EDTA-2Na and ASA were added to the photocatalytic reaction system, the degradation rate of the sample to TCH solution decreased more. The degradation rate of the sample to the TCH solution decreased more, and the effect size of these three radical trappers was EDTA-2Na\u0026thinsp;\u0026gt;\u0026thinsp;ASA\u0026thinsp;\u0026gt;\u0026thinsp;IPA, indicating that h\u003csup\u003e+\u003c/sup\u003e was the main active species and \u0026bull;O\u003csup\u003e2\u0026minus;\u003c/sup\u003e was the secondary active species in this system.\u003c/p\u003e\u003cp\u003e4.7 Photocatalytic Mechanism Analysis\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe photocatalytic mechanism of 1.0% CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e15\u003c/span\u003e. Since La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and CuO form a type I heterojunction, h\u003csup\u003e+\u003c/sup\u003e on La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e VB can jump to VB of CuO, and e\u003csup\u003e\u0026minus;\u003c/sup\u003e on La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e CB will jump to CB of CuO. The CNTs in the geopolymer microspheres can act as electron acceptors, and e\u003csup\u003e\u0026minus;\u003c/sup\u003e can be migrated from the CB of CuO to the CNTs, and the e\u003csup\u003e\u0026minus;\u003c/sup\u003e migrated to the CNTs reacts with the O\u003csub\u003e2\u003c/sub\u003e molecules adsorbed on the photocatalytic microspheres to generate \u0026bull;O\u003csup\u003e2\u0026minus;\u003c/sup\u003e, and the h\u003csup\u003e+\u003c/sup\u003e on the CuO VB reacts with the H\u003csub\u003e2\u003c/sub\u003eO adsorbed on the photocatalytic microspheres to generate -OH and H\u003csup\u003e+\u003c/sup\u003e, the h\u003csup\u003e+\u003c/sup\u003e, \u0026bull;O\u003csup\u003e2\u0026minus;\u003c/sup\u003e and \u0026bull;OH with strong oxidative properties achieve the oxidative decomposition of TCH molecules. The conductivity of the microspheres was increased by the introduction of CNTs so that they acted as electron acceptors and provided channels for the migration of photogenerated electrons, which inhibited the recombination of photogenerated carriers and improved the photocatalytic activity of the samples. In addition, the specific surface area and pore structure of the photocatalytic materials were improved by doping CNTs, and the multi-porous structure and excellent adsorption of the microspheres provided more active sites for the photocatalytic reaction, and the three-dimensional skeleton structure of the geopolymer contained Bronsted acidic sites (Si-O-H\u003csup\u003e+\u003c/sup\u003e), which could be combined with h\u0026thinsp;+\u0026thinsp;to generate \u0026bull;OH, which has the effect of promoting the effective separation of h\u003csup\u003e+\u003c/sup\u003e and e\u003csup\u003e\u0026minus;(Wang et al. 2018)\u003c/sup\u003e. Thus, the photocatalytic activity of the composites was further enhanced by the doping of CNTs in the geopolymer microspheres.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn this paper, CNTs-modified geopolymer microspheres (GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e) were prepared by a suspension-dispersion technique using metakaolin and alkali exciters as raw materials, and carbon nanotubes (CNTs) were doped into the precursor to improve the electrical conductivity and morphology structure of geopolymers. Then the photocatalytic material 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e was prepared in the carrier of GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e.The photocatalytic activity was evaluated by visible-light catalytic degradation of TCH solution, and the effect of the optimal doping amount of CNTs (wt%) on the photocatalytic performance was explored. The experimental results showed that the photocatalytic activity of 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e was optimal when the doping amount of CNTs was 0.5 wt%, and the degradation performance of CNTs could reach 89.51% of 50 mL of 30 mg/L TCH solution within 100 min under the irradiation of can be light, and the proposed first-order kinetic constant of its degradation of TCH was 1.25 times higher than that of undoped CNTs. The CNTs-modified microspheres have a more porous structure and larger specific surface area, which can provide more active sites for the photocatalytic reaction. After doping CNTs into the geopolymer precursor, the conductivity of the samples increased, the photocatalytic materials showed stronger absorption of visible light, the forbidden bandwidth decreased from 1.80 to 0.39 eV, and the recombination of the photogenerated electron-hole pairs was significantly inhibited. As a result, the 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5% CNTs\u003c/sub\u003e exhibited higher photocatalytic activity.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgements\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by the Local Science and Technology Development Fund Projects Guided by the Central Government of China (2021ZYD0060), the Science and Technology Project of Southwest Petroleum University (2021JBGS03), the Chengdu International Science and Technology Cooperation Fund\u0026nbsp;（2020GH0200069HZ）.\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eOpen access funding provided by Science and Technology Project of Southwest Petroleum University (2021JBGS03). This research was supported by Chengdu International Science and Technology Cooperation Fund\u0026nbsp;（2020GH0200069HZ）.\u003c/p\u003e\n\u003cp\u003eAuthors\u0026rsquo; Contributions\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the conception and design of the study.Methodology, software, validation,\u0026nbsp;investigation, data curation, formal analysis, and writing-original draft were conducted by Xiaomin Zhang, with revisions provided by all authors.Bo Yu and Jing yang contributed to theresources, data Curation, visualization, investigation, and formal analysis. Lianhong Zhangcontributed to the methodology, funding acquisition, resources, writing-review \u0026amp; editing, and project administration.\u0026nbsp;The first draft of the manuscript was written by Xiaomin Zhang, and all authors reviewed, provided feedback, and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003eCorresponding author\u003c/p\u003e\n\u003cp\u003eCorrespondence to Lianhong Zhang.\u003c/p\u003e\n\u003cp\u003eEthical approval\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003eConsent to participate\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003eConsent to publish\u003c/p\u003e\n\u003cp\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003eCompeting Interests\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003eData Availability Statement\u003c/p\u003e\n\u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbou-Gamra ZM, Ahmed MA (2016) Synthesis of mesoporous TiO\u003csub\u003e2\u003c/sub\u003e-curcumin nanoparticles for photocatalytic degradation of methylene blue dye. 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Int J Hydrog Energy 42:20589\u0026ndash;20598\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Geopolymer microspheres, Photocatalysis, Heterojunction, Carbon nanotube, Tetracycline hydrochloride","lastPublishedDoi":"10.21203/rs.3.rs-7126019/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7126019/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCNTs-modified geopolymer microspheres (GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e) were synthesized by adding carbon nanotubes (CNTs) into the geopolymer precursors. And, the Cu-La supported modified geopolymer photocatalysts (1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e) were prepared by using GM\u003csub\u003ex wt%CNTs\u003c/sub\u003e as the carrier. Photocatalytic experiments showed that 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e had the highest photocatalytic activity when CNTs were doped at 0.5 wt%, and the degradation rate of 30 mg/L TCH solution reached 89.51% when irradiated with visible light for 100 min, and 1.0%CuO/7.5%La\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e@GM\u003csub\u003e0.5%CNTs\u003c/sub\u003e had good salt resistance, recycling stability and universality, and the free radical capture experiments found that h\u003csup\u003e+\u003c/sup\u003e was the main active species in this photocatalytic system, with \u0026bull;O\u003csup\u003e2\u0026minus;\u003c/sup\u003e was the secondary active species. Characterization analysis showed that by doping CNTs, the conductivity of the material was increased and the resistance of charge transfer at the interface of the material was reduced, which improved the separation efficiency of photogenerated electron-hole pairs, and enabled the catalysts to exhibit a stronger response to visible light. In addition, the CNTs-modified microspheres possessed a more porous structure and larger specific surface area, which provided more active sites for photocatalytic reactions.\u003c/p\u003e","manuscriptTitle":"CNTs modified geopolymer microspheres loaded with Cu-La bimetallic composites and its photocatalytic performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-07 08:46:14","doi":"10.21203/rs.3.rs-7126019/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-08-03T07:43:24+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-03T07:24:58+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2025-07-24T10:30:50+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-18T05:40:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2025-07-17T05:11:40+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4996e7d9-a401-4a90-9df3-744459930f63","owner":[],"postedDate":"August 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-08-07T08:46:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-07 08:46:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7126019","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7126019","identity":"rs-7126019","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}