Degradation of Phenol by Photocatalysis Using TiO2/Montmorillonite Composites Under UV Light

Degradation of Phenol by Photocatalysis Using TiO2/Montmorillonite Composites Under UV Light | 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 Degradation of Phenol by Photocatalysis Using TiO 2 /Montmorillonite Composites Under UV Light Huijuan Li, Yeting Yao, Xiaoyan Yang, Xusheng Zhou, Ran Lei, Shufang He This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-848926/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Composites of Titanium (IV) oxide combined with montmorillonite (MMT) with various TiO 2 /MMT were prepared for photocatalysis application. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance UV–visible spectroscopy. The main influential factors such as the TiO 2 /MMT dose, calcined temperature and pH value of the solution were studied. The main intermediates of phenol degradation were determined by High Performance Liquid Chromatography (HPLC). The results showed that the average size of TiO 2 nanoparticles was decreased from 22.51 nm to 10.66 nm through the immobilization on MMT. The components in the interlayer domain were replaced by titanium pillars, and the pillaring reaction proceeded in the interlayer domain, and the basic skeleton of MMT was unchanged, and also TiO 2 was dispersed on the surface of the MMT. When the initial concentration of phenol is 10 mg/L, the phenol solution pH is 6 and the UV light irradiation time is 240 min, the phenol degradation rate of 30%TiO 2 /MMT composite is 89.8%, which is better than MMT (11.5%) and pure TiO 2 (58.8%). It shows that TiO 2 loaded on MMT improves its photocatalytic activity. The phenol reaction process detected by HPLC showed that it had undergone through hydroquinone and benzoquinone, and finally converted into maleic acid and carbon dioxide and small molecules. The possible photocatalysis mechanism is presented. Toxicology Montmorillonite Titanium dioxide Sol-gel method Phenol degradation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction Phenol and its derived compounds are one of the most toxic, and are used widely in petrochemical, chemical, and pharmaceutical industries. When they enter into the natural waters will cause serious pollution and great harm to environment. Drinking water containing phenols may cause severe renal insufficiency, convulsions, and even death (Ruikun Wang 2019). Phenol degradation techniques include adsorption, extraction, electrolysis and photocatalytic oxidation (Lingeswarran Muniandy 2014). Among them, TiO 2 -based catalysts can handle with higher concentrations of phenol-containing wastewater, mild reaction conditions, high treatment efficiency and no secondary pollution, and is widely used as photoelectric conversion, photochemical synthesis, and photocatalytic oxidation of environmental pollutants (Paulina Górska 2009; Ali Gundogdu et al. 2012 ). However, poor adsorption, narrow absorption spectrum and difficult recovery of nanoparticles of TiO 2 limit its application in water treatment (Sreenivasan Koliyat Parayil 2012). Montmorillonite (MMT) is a layered aluminosilicate mineral, its theoretical molecular formula is N z+ χ/z M 6 2+ [Si 8 − χ Al χ ]O 20 (OH) 4 ·nH 2 O. The unit is composed of two layers of silicon-oxygen tetrahedron with a layer of aluminum-oxygen octahedron. It belongs to a 2:1 type structure with swellable hydrous aluminosilicate. The special crystal structure makes montmorillonite have ion exchange capacity and dispersion suspension stability. It possesses layered structures, larger interlayer distance, specific surface area and thermal stability, which can be obtained through physical and chemical methods such as pillaring, insertion replacement and ion exchange (Hassan Ouachtak 2021). Y. X. Liu studied the commercially available montmorillonite KSF as photoactive reagent and utilized for BPA photodegradation, and found that the BPA degradation increased with the concentration of clays in the range of 0.5 g/L to 5 g/L. The photodegradation rate of BPA is fitted well into the Langmuir-Hinshelwood equation (Y. X. Liu 2008). K. Mogyorósi et al prepared clay mineral intercalated TiO 2 nanoparticles, and found that calcination was not necessary for nanocomposites preparation that had high specific surface areas and well-crystallized anatase contents and thus could be used as an efficient photocatalyst(K. Mogyoro´si 2003). Daimei Chen et al. synthesized TiO 2 pillared montmorillonite and investigated as methylene blue photocatalytic activity, the prepared TiO 2 /MMT composites exhibited superior photocatalyic property and the maximum removal efficiency was up to 98% within 90 min (Daimei Chen 2012). In this paper, TiO 2 /MMT composites were prepared by a sol-gel method. The phenol solution was used as model degradation molecular. The effects of TiO 2 loading amount, calcination temperature and solution pH on the degradation of phenol by TiO 2 /MMT composites were investigated. FTIR, XRD and SEM techniques were used to characterize the prepared composites. Experimental 1.1. Materials The montmorillonite (MMT) was supplied from Xinghe County, Inner Mongolia, China (purity 85%, the major compositions is: SiO 2 , 78%; Al 2 O 3 ,11.63%; MgO, 3.71%; Fe 2 O 3 , 2.81% and CaO is 2.03%). (C 4 H 9 O) 4 Ti, (CR, Sinopharm Chemical Reagent (Shanghai) Co., Ltd .; The components of MMT are shown in Table.1; Phenol, AR, Chengdu Kelong Chemical Reagent Factory; Sodium Chloride, AR, Chengdu Kelong Chemical Reagent Factory; 4-Aminoantipyrine, CR, Shanghai Qiangshun Chemical Reagent Co., Ltd.; Potassium ferricyanide, CR, Shanghai Qiangshun Chemical Reagent Co., Ltd .; 1.2 Sample preparation (1) Modification of montmorillonite (MMT) Montmorillonite (Ca-MMT, 100g) was dispersed into 1000 mL 1.0 mol/L NaCl solution, and stirred for 2 h at 60℃ water bath. Then, the resulting suspension was separated by centrifugation and washed with distilled water until no Cl - (using 0.1 mol/L AgNO 3 test), dried at 110℃ for 24 h, ground, sodium montmorillonite (Na-MMT) can be obtained after 100 mesh. (2) Preparation of TiO 2 TiO 2 was synthesized through sol-gel method. 5 mL Tetrabutyl titanate was dissolved in 7 mL anhydrous ethanol under vigorous stirring. At the same time, the above solution was dropwise added to a mixture with 15 mL ethanol, 8 mL deionized water and 2 mL acetic acid to make a solution. Under vigorously stirring conditions, the viscosity of the mixed solution turns more and more and then changed into a sol. The product was aged for 24 h, dried at 110 ℃ for 24h and finally at different temperature for 4h. (3) Preparation of TiO 2 /MMT The TiO 2 sol was mixed with a certain percent of modified Na-MMT aqueous suspension. In this mixed suspension. The beaker was rinsed with absolute ethanol and thoroughly stirred to prepare TiO 2 /MMT. Aging for 24h, the sol was dried at 110℃ for 24 h, and then placed in a muffle furnace (Shanghai Chongming Experimental Instrument Factory) and calcined at a certain temperature (300–600℃) for 4 h, a modified TiO 2 /MMT is obtained (named as TiO 2 /MMT, which is the mass percentage of TiO 2 and MMT, such as 40% TiO 2 /MMT means that the TiO 2 mass is 0.4 and the MMT mass is 1.00). 1.3 Characterization The as-prepared samples were characterized by different techniques. The crystalline phases of the TiO 2 /MMT composites were investigated with X-ray diffraction (XRD, Rigaku D/Max 2000, Cu Kα radiation source with wavelength of λ = 0.15418 at 40 kV and 30 mA). The Fourier transform infrared (FT-IR) spectra were recorded on a Spectrum 100 spectrometer (BRUKER TENSOR27). Transmission electron microscopy (TEM, JEOL LEM-100CXII) and scanning electron microscope (SEM, S-3000N, Hitachi, Japan) was used to observe the microstructure of as-prepared composites. Using BaSO 4 as the reflectance sample, the UV–vis diffuse reflectance spectra were recorded with a HITACHI U-3010 spectrometer. 1.4 Photocatalytic degradation of phenol The photocatalytic activities of the produced TiO 2 /MMT composites were measured by degrading phenol. In each experiment, 0.2 g photocatalyst was added to 100 mL solution (10 mg/L, the initial pH is 6, if the pH needs change, adjust with acetic acid and ammonia). of the pollutants and stirred in dark for 30 min in order to reach an adsorption-desorption equilibrium. Then, the suspension was irradiated with a UV light source (300 W, Optima wavelength 365 nm). During the irradiation period, an aliquot of 2.0 mL suspension was collected at regular 30 min intervals, centrifuged to remove the photocatalyst, the aliquots were immediately centrifuged and analyzed using UV–vis spectrometer (UV-1800, Shimadzu). In order to quantify the evolution of intermediate products, the extinction coefficients of maleic acid (MA), fumaric acid (FA), hydroquinone (HQ), catechol (CC), benzoquinone (BQ), and phenol (PhOH) were measured independently. The concentrations of phenolic compounds were calculated using high performance liquid chromatography (HPLC, PerkinElmer Altus 30) equipped with a Sinochrom ODS-BP column (3.5 µm; 4.6×250 mm) and a 220/240 pump, and also equipped with a Spectra 100 UV–Vis detector to identify the degradation products as an evaluation of the photocatalytic activity of the synthesized TiO 2 /MMT composites. A mobile phase composition of methanol / NaH 2 PO 4 (with 0.5 mol/L) ratio was 70:30. The mobile phase was delivered at a flow rate of 1.0 mL /min and the detection wavelength was set at 254 nm. The 10 uL solutions were filtered on a 0.45 µm cellulosic filter before injected into the HPLC chromatography. Results And Discussion 2.1 XRD results 2 The XRD pattern of the as-prepared pure MMT, TiO 2 and 30%TiO 2 /MMT catalysts are shown in Fig. 1. For pure montmorillonite, the diffraction peak at 2θ = 19.77°,21.85° and 26.76° attribute to the Si-O-Si diffraction peak of Na-montmorillonite, the Si-O-Al and the (101) of quartz, respectively. The original montmorillonite sample (MMT) shows a series of reflections at 2θ = 18.64° with d003 = 0.448 nm and 2θ = 19.77° with d100 = 0.449 nm, respectively. According to the JCPDS card (NO. 00-003-0010), it is corresponding to Na-montmorillonite (Hongjuan Sun 2015). The diffraction peaks of TiO 2 at 2θ = 25.2°, 38.1°, 47.7° and 54.4° correspond to those of anatase (101), (004), (105) and (204), respectively. At the same time, there is a rutile characteristic diffraction peak (2θ = 27.43°) for pure TiO 2 (600 ℃, 4 h) and 30%TiO 2 /MMT (700 ℃, 4 h) which suggests that the montmorillonite as a carrier can increase TiO 2 phase transition temperature, and make it still anatase phase after calcined at 600 ℃. The positions of the characteristic diffraction peaks of montmorillonite in the 30%TiO 2 /MMT composite calcined at different temperatures has no obvious change, and the peak strength is weaker. It can be seen that the introduction of TiO 2 do not change the structure of montmorillonite. The diffraction peaks of TiO 2 /MMT at 2θ = 26.76° and 31.02° are obviously weakened or even disappeared compared with the original montmorillonite, which indicates that the original Si-O-Al bond was destroyed, and a new Si-O-Ti bond is constructed after replaced the aluminum ion in the interlayer (Lila Djouadi 2018). The average crystal size of the particles can be estimated from the widths of TiO 2 /MMT composites reflections by using the Scherrer formula, d = 0.89·λ/(β·cosθ), where λ (1.5413 Å) is the wavelength, θ is the Bragg angle (°), d is the average crystallite size (nm) and β is the full width at half-maximum. The calculated data of the five TiO 2 -based catalysts are followed in Table 2 . Table 2 Crystalline size of TiO 2 in different samples Sample d/nm TiO 2 (600℃,4h) 22.51 30%TiO 2 /MMT (400℃,4h) 6.61 30%TiO 2 /MMT (500℃,4h) 7.68 30%TiO 2 /MMT (600℃,4h) 10.66 30%TiO 2 /MMT (700℃,4h) 29.50 It can be seen from Table.2, The grain size of TiO 2 reduces from 22.51 nm to 10.66 nm for pure TiO 2 and 30%TiO 2 /MMT calcined at 600℃ for 4h, indicating that the particle size of TiO 2 pillared montmorillonite decreased effectively. And the crystalline size of TiO 2 in 30% TiO 2 /MMT composites calcined at different temperatures also gradually increased with the temperature. 2.2 SEM and TEM Figure 2 shows SEM images of raw montmorillonite (a) and TEM images of pure TiO 2 (b) and 30% TiO 2 /MMT (c) composites calcined at 600 ℃ for 4h. The raw montmorillonite shows larger particle aggregates with a flower-like layer structure, the flaky structure is relatively close. For the pure TiO 2 , the particles is relatively uniform, with some agglomeration, which may be related to the higher calcination temperature, the particle size is about 19 nm. For the 30% TiO 2 /MMT (600℃, 4h) composite, it can be observed the larger platelets and layer structure of montmorillonite clearly. Since the TiO 2 nanoparticles were intercalated, the layer space was enlarged and the structural layers of montmorillonite were separated (R. Djellabi 2014 ). Although the montmorillonite layers were still largely parallel, they lost long-range order in the c direction after TiO 2 intercalation. Which is consistent with the disappearance of the (001) reflection in the XRD patterns(Ping Zhang 2009). The lattice fringe image of the original montmorillonite sample shows that the structural layers are orderly with a layer space of 2.84 nm. And there are a lot of small aggregates, which are probably broken platelets and agglomerates of TiO 2 crystallites caused by the hydrolysis of surface Ti(OC 4 H 9 ) 4 (Boualem Damardji 2008). TiO 2 particle size is about 10 nm by calculation, which is consistent with the data calculated by Scherrer formula in XRD. At the same time, TiO 2 pillared montmorillonite decreases its particle size from 19 nm to 10 nm, while the layered structure of montmorillonite remains unchanged, which also make TiO 2 /MMT composites keep good adsorption efficiency of montmorillonite, and then enhance the phenol degradation activity of TiO 2 /MMT. 2.3 FT-IR characterization Figure 3 presents FT-IR spectra of different samples of TiO 2 , MMT and TiO 2 /MMT dried at 110℃ and calcined at 600 ℃ for 4h, respectively. For the purified MMT, the broad band at 3422 cm − 1 is due to the stretching vibration of the hydroxyl group and the interlayer water molecules. And the weak peak at 3624 cm − 1 is attributed to -OH stretching vibration of Al-O-H. Bands at 1645 cm − 1 and 1468 cm − 1 are caused by the bending vibration of the hydroxyl group and the interlayer water molecules. The vibration peak at 1079 cm − 1 is caused by the antisymmetric stretching vibration of Si-O-Si in montmorillonite, which caused by the strong hydration of Ca, Mg and Al plasma strengthens the hydrogen bond between the surface of montmorillonite layer and water, weakens and disappears the band of Si-O bond, resulting in the changing of Si-O and Si-O-Si into a single peak (Ke Chen 2001). Bands at 845 cm − 1 and 794 cm − 1 attribute to the bending vibration peak of Mg 2+ -OH and the hydroxyl vibration of MgAl-OH, respectively. And also bands at 521 cm − 1 , 474 cm − 1 and 916 cm − 1 are suggested to the bending vibration of Si-O-Al, Si-O-Si and octahedral Al-O(OH)-Al in montmorillonite independently. The broad peak at 587 cm − 1 is attributed to Ti-O bond vibration, which indicates that TiO 2 is amorphous. After TiO 2 modified MMT, interlayer water and hydroxyl increased, which restricted the vibration of structural hydroxyl Al-OH. The peak at 3621 cm − 1 lost, and the two peaks at 1021 and 917 cm − 1 appeared, it shows that the composition of the interlayer of montmorillonite changed after TiO 2 was introduced, and the in-plane stretching vibration peaks of Ti-O-C and Si-O-Si generated (Lingling Yuan 2011; Chihiro Ooka et al. 2003 ). Also at 796 cm − 1 , the absorption of the hydroxyl vibration peak of MgAl-OH weakened, which may be related to the removal of hydroxyl as octahedron Ti hydrated ions into the interlayer. At the same time, the strength of 521 cm − 1 peak in the composite is obviously weakened and widened, which is the superposition of Ti-O and Si-O absorption peaks. The results show that the strength of Si-O bond is also affected by titanium in lay. For the 30% TiO 2 /MMT calcined at 600℃ for 2h, 3422 cm − 1 and 916 cm − 1 disappear, while 1468 cm − 1 peak strength decreases, indicating that interlayer water lost. The vibration peak of Ti-O becomes narrow at 600 cm − 1 , indicating the TiO 2 crystal phase formed. At the same time, the 1070 cm − 1 peak of 30% TiO 2 /MMT changed into a single peak, which seems that the basic framework of MMT remained unchanged and remained the original structure. For the 30%TiO 2 /MMT calcined at different temperatures, it can be seen that the peaks at 3625 cm − 1 , 1030 cm − 1 and 845 cm − 1 gradually disappear, and the peaks of 3431 and 1648 cm − 1 gradually decrease, which is caused by the evaporation of interlayer water (V. Makrigianni 2015). 2.4 UV-ViS Figure 4 shows diffuse reflectance UV-Vis spectra of 30% TiO 2 /MMT calcined from 400–700℃. It can be seen from the Fig. 4 that the absorption band of pure TiO 2 at 200–400 nm belongs to the electron coordinated by the titanium coordinated oxygen atom to the empty orbit of the central titanium atom, the characteristic absorption formed by OB 2p →TiB 3dB charge transfer, in which the tetrahedron at 248 nm. The characteristic peak of coordination titanium, the absorption peak around 337 nm was the absorption peak of octahedral coordination titanium(Aydin Hassani 2015). The peaks of 30% TiO 2 /MMT composites calcined at different temperatures around 433 and 504 nm are Fe-O absorption peaks of Fe 2 O 3 , because of the used montmorillonite content of 2.8% Fe 2 O 3 . At the same time, 30% TiO 2 /MMT composites calcined at different temperatures have a strong light absorption performance. The value Eg was deliberate from the UV–visible pattern of the titled TiO 2 /MMT by extrapolating the line through the k axis and it is exposed in Fig. 4. The wavelength maxima had 409.6 nm (pure TiO 2 ), 427.1 nm (30%TiO 2 /MMT, 400℃), 434.7 nm (30%TiO 2 /MMT, 500℃), 418.4nm (30%TiO 2 /MMT, 600℃), and 451.5nm (30%TiO 2 /MMT, 700℃), respectively. Since the photoabsorption performance of the photocatalyst is positively related to the photocatalytic degradation activity of phenol, it was confirmed that the 30% TiO 2 /MMT(600℃,2h) prepared by the sol-gel method has the best photocatalytic activity for phenol degradation. 2.5 Photocatalytic activity 2.5.1 Effect of TiO 2 loading amount on TiO 2 /MMT Figure 5 shows the phenol removal efficiency under UV light over MMT, TiO 2 and different loading of TiO 2 on TiO 2 /MMT calcined at 600℃ for 4h. The results showed that the photolysis of phenol in the absence of photocatalyst is only 1.5%, which can be neglected. And the phenol degradation is 11.5% over MMT which shows that MMT has a certain adsorption capacity for phenol solution, but the adsorption activity was very low. It has 58.5% photocatalysis activity over pure TiO 2 . Also, for different amount loading of TiO 2 /MMT, the results indicated that the photo degradation efficiency of phenol increased with TiO 2 content until 30%TiO 2 , then decreased after more TiO 2 loading. Because TiO 2 was the active center of the photocatalytic reaction, when its loading is less, the phenol degradation is low. When the loading of TiO 2 was overdose, photo-generated electrons and holes were generated under light conditions, and the photo-generated electrons and holes recombine to form a composite band, which affects the formation of hydroxyl active groups, reduces the utilization of ultraviolet light, causes degradation efficiency reduced. It was concluded that the photocatalytic activity of 30% TiO 2 /MMT composites has the best phenol degradation performance under ultraviolet light. Theoretically, the adsorption and degradation activity of TiO 2 /MMT composites on phenol was the sum of the phenol adsorption on montmorillonite and photodegradation over pure TiO 2 . However, it can be seen from the Fig. 5, the phenol adsorption rate of montmorillonite to 11.5% and the degradation rate of TiO 2 was 58.8% after 240 minutes under UV light, the sum of the two was only 70.3%, which is significantly lower than the 30%TiO 2 /MMT composite (89.75%). On the one hand, the loading of montmorillonite may increase the crystalline phase transition temperature of TiO 2 to a certain extent; it still maintains the anatase phase structure at 600℃. And also increases the degree of TiO 2 dispersion and makes its particles smaller, which contributed to improving the phenol degradation over TiO 2 /MMT composites(Hongjuan Sun 2015). 2.4.2 Effect of calcined temperature Figure 6 shows the phenol photocatalytic degradation over 30%TiO 2 /MMT composites calcined at different temperatures (from 300 to 700℃). For the 30%TiO 2 /MMT composites calcined from 300℃ to 600℃, it can be seen that the degradation rate gradually increased with roasting temperature. When calcined at 600℃, the phenol degradation rate reached 89.75%, but is only 15.08% when the roasting temperature is 700℃, decreased significantly. Therefore, in this catalytic reaction system, the optimal calcination temperature of 30% TiO 2 /MMT photocatalytic composite is 600℃. 2.5.2 The effect of the initial pH The solution pH is one of the important parameters that can markedly affect the photocatalytic process. In the present work, the effect of the initial pH on the phenol photocatalytic degradation efficiency was studied in the pH range of 2–12 (Fig. 7). In this experiment, acetic acid and ammonia are usually used to adjust the pH value of the solution. The results indicated that the degree of photodegradation efficiency increased with the pH values from 2 to 6 and then decreased. It can be seen from Fig. 7 that the photocatalytic performance of the reaction solution under slightly acidic conditions was significantly higher than that obtained under slightly alkaline conditions, the pH value will change the interfacial charge of the TiO 2 /MMT, thereby changing the dispersion of the particles in the solution, and affecting the adsorption behavior of the montmorillonite matrix on the catalyst surface. In the photocatalyst reaction, the electrons were excited from the valence band to the conduction band, forming electrons (e − ) and holes (h + ). The highly active holes consume OH − in water during the reaction and oxidize them to have strong oxidative active๒OH, then e − and h + undergo redox reactions with substances dispersed in water; As the pH value increases, the concentration of OH − in the solution sharply increases, then the concentration of · OH increased significantly, the conduction electrons reacted with the adsorbed O 2 to form O 2 − , which could also generate · OH with H 2 O, so the degradation efficiency increased with the pH value. However, too high a concentration of · OH will cause a decrease in photocatalytic activity (Chunquan Li 2021). Therefore, the photocatalytic effect was better under suitable pH conditions, which has a high photocatalytic degradation rate under acidic conditions. 2.5.2 The effect of 30%TiO 2 /MMT (600℃,4h) dosage Catalyst dosage is an important parameter in heterogeneous photocatalytic reaction. In order to determine the effect of catalyst dosage on the phenol photodegradation, experiments were carried out by varying the amount of 30%TiO 2 /MMT from 0.1 to 0.4 g (Fig. 8). Increasing the amount of photocatalyst from 0.1 g to 0.2 g resulted in increasing the photodegradation efficiency from 42.25–89.96% at the reaction time of 240 min, respectively. By adding the catalyst dosage, promoted the production of reactive species. However, more catalyst dosage would also induce greater aggregation of the catalysts and added the turbidity of the solution, reduce the degree of light penetration through the solution and thereby leading to a reduction in the phenol degradation efficiency. Therefore, 0.2 g 30%TiO 2 /MMT photocatalysts is the best amount for phenol photocatalytic reaction(Shivatharsiny Rasalingama 2014). 2.5.3 High performance liquid chromatography -(HPLC) analysis HPLC was employed to identify the degradation products in order to evaluate the catalytic activities over the pure TiO 2 (600°C, 4 h) and 30% TiO 2 /MMT (600°C, 4 h) photocatalysts. Under our experimental conditions, benzoquinone (BQ), hydroquinone (HQ), maleic acid (MA), and fumaric acid (FA) have been identified as intermediates. It should be noted that the four compounds comprising were produced in significant amounts during photocatalytic degradation with the two photocatalysts. For the pure TiO 2 , the phenol concentration gradually decreased with the reaction time. It found that the four materials (HQ, BQ, MA and FA) are the main aromatic compounds produced by phenol conversion. The highest concentration of the four materials are detected at 210 min and then decreased gradually, also the MA and FA keep the higher concentration than BQ and HQ, which mightbe caused by the BQ and HQ can turn into MA and FA or the phenol itself will be further converted into maleic acid and fumaric acid, and the residual phenol concentration was 27.17 mg/L after reaction for 420 min. During the phenol photocatalytic degradation over TiO 2 , phenol is gradually degraded in the progress of the reaction, and most of it is directly mineralized into CO 2 and water (Asma Turki 2014). For the 30% TiO 2 /MMT catalyst, with the extension of the photocatalytic reaction time, the phenol concentration in the residual solution decreased significantly. After 420 min reaction, the residual phenol concentration was 9.36 mg/L. Total benzoquinone (HQ), hydroquinone (BQ), maleic acid and fumaric acid (FA + MA) produced by the photocatalytic degradation system of 30%TiO 2 /MMT. Compared with the pure TiO 2 system, 30%TiO 2 /MMT had more phenol photo-degradation efficiency, and the total amount of intermediate products detected is larger than that in the TiO 2 system. The larger amount of HQ + BQ is due to the higher selectivity of 30%TiO 2 /MMT in the phenol conversion. The loading of montmorillonite makes๒OH produced by TiO 2 easier to attack the para position of phenol. Hydroquinone is produced and further converted into p-benzoquinone. The amount of butadionic acid (FA + MA) detected in the reaction system of 30%TiO 2 /MMT for phenol degradation was higher than that of pure TiO 2 . Considering the production of HQ + BQ and FA + MA amount produced in this system, their concentration increased first and then decreased. It is speculated that the reaction course of the montmorillonite loading system may be the rapid phenol mineralization to produce CO 2 + H 2 O. The amount of acid produced was small, or is rapidly converted to CO 2 under these catalytic conditions (Xiaobo Wang 2014). The conversion of phenol calculated by liquid chromatography data was 45.7% (TiO 2 ) and 81.9% (30%TiO 2 /MMT), respectively. It was found that the sum of the carbon content of the intermediate substances was much lower than the degradation rate caused by phenol. It is possible that a large amount of carbon was converted into carbon dioxide, leaving the reaction system. In addition, it can be seen from Fig. 10 that almost all the intermediate products of phenol degradation are converted into small molecular substances. With reference to high-performance liquid reaction data and a large amount of literature, it is concluded that under this experimental condition, the reaction mechanism of phenol degradation may be like this: The good photocatalytic activity of the 30%TiO 2 /MMT composites can be ascribed to the following reasons. The photocatalytic mechanism of 30%TiO 2 /MMT composites is showed in Fig. 10. TiO 2 in the interlayer of MMT could increase the surface area of TiO 2 /MMT composites,and adding the adsorption efficiency of phenol༌thus promoting the photodegradation efficiency of 30%TiO 2 /MMT. Secondly, TiO 2 loaded on the surface of MMT and improved its disperse, also enlarged the amount of exposed activates for reactions. When the composite photocatalyst is irradiated by sunlight, the electrons (e − ) in the valence band (VB) of TiO 2 will be excited by energy and transfer to the conduction band (CB) to generate photogenerated electrons, which will generate photogenerated holes (hv + ), Photogenerated holes and electrons will combine with water and dissolved oxygen in water to form superoxide radical (· O 2 − ) and hydroxyl radical (· OH). The two radicals can oxidize phenol to HQ + HQ, and then convert into FA + MA, and finally mineralize into small molecules of H 2 O and CO 2 . Conclusions 1)TiO 2 /MMT composites were prepared by sol–gel method. The experiment results indicate 30%TiO 2 /MMT (600℃,4h) has relatively higher photocatalytic activities than other catalysts. A certain amount of TiO 2 (TiO 2 /MMT = 30%) is highly dispersed on MMT surface, and also TiO 2 can cause the layer silicate of MMT to behave as barriers layer of preventing TiO 2 powders from agglomeration and reduce its particle size from 22.51 to 7.68 nm. Besides, the best photoactivity of 30%TiO 2 /MMT composites can be due to its smaller particle size, its layer structure and the red shift of the onset absorption edge in the UV–Visible DRS. 2)The initial concentration of phenol was 10 mg/L, the initial pH of the solution was 6, the amount of catalyst used was 2 g/L, and the ultraviolet irradiation time was 240min. Under the condition of, the degradation rate of phenol was 89.8%. For phenol with an initial concentration of 50 mg/L, the phenol conversion detected by liquid chromatography reached 81.9% at 420 min. The phenol degradation rate was much higher than that of pure TiO 2 (45.7%) under the same conditions, indicating that the loading of montmorillonite significantly enhanced the photocatalytic degradation of phenol by TiO 2 . Declarations Acknowledgement: The present study was supported by the Joint Project of Basic Agricultural Research Fund of Yunnan Province (2018FG001-051). The manuscript does not applicable for ethical approval and consent to participate. This study was supported in part by grants from the Joint Project of Basic Agricultural Research Fund of Yunnan Province (2018FG001-051). And all the authors consent to publish. The authors declare that they have no competing interests. All data generated or analyzed during this study are included in this published article. The authors’ contributions are followed as: Huijuan Li contributed to the conception of the study and wrote the manuscript; Yeting Yao contributed significantly to analysis and manuscript preparation Xiaoyan Yang contributed to make the graphs in the manuscript. Xusheng Zhou performed the experiment; Ran Lei performed the data analyses; Shufang He helped perform the analysis with constructive discussions. References Gundogdu A, Duran C, Basri Senturk H, Soylak M, Ozdes D, Serencam H, Imamoglu M (2012) Adsorption of Phenol from Aqueous Solution on a Low-Cost Activated Carbon Produced from Tea Industry Waste: Equilibrium, Kinetic, and Thermodynamic Study [J]. Chem Eng Data 57:2733–2743. https://doi.org/10.1021/je300597 Aydin Hassani A, Khataee S, Karaca (2015) Photocatalytic degradation of ciprofloxacin by synthesized TiO 2 nanoparticles on montmorillonite: Effect of operation parameters and artificial neural network modeling [J]. J Mol Catal A: Chem 409:149–161. http://dx.doi.org/10.1016/j.molcata.2015.08.020 Asma Turki C, Guillard, Frédéric Dappozze, Zouhaier Ksibi ,GillesBerhault, Hafedh Kochkar, Phenol photocatalytic degradation over anisotropic TiO 2 nanomaterials: Kinetic study adsorption isotherms and formal mechanisms [J] (2015) Appl Catal B 163:404–413. http://dx.doi.org/10.1016/j.apcatb.2014.08.010 Boualem Damardji HK, Duclaux L, David B (2009) Preparation of TiO 2 -pillared montmorillonite as photocatalyst Part I. Microwave calcination, characterisation, and adsorption of a textile azo dye [J]. Appl Clay Sci 44:201–205. . 10.1016/j.clay.2008.12.010 Chihiro Ooka H, Yoshida M, Horio K, Suzuki T, Hattori (2003) Adsorptive and photocatalytic performance of TiO 2 pillared montmorillonite in degradation of endocrine disruptors having different hydrophobicity [J]. Appl Catal B 41:313–321. https://doi.org/10.1016/S0926-3373(02)00169-8 Li C, Zhu N, Yang S, He X, Zheng S, Sun Z, Dionysios D, Dionysiou, A review of clay based photocatalysts: Role of phyllosilicate mineral in interfacial assembly, microstructure control and performance regulation [J], Chemosphere, 2021 273., 129723, https://doi.org/10.1016/j.chemosphere.2021.129723 Chen D, Zhu Q, Zhou F, Deng X, Li F, Synthesis and photocatalytic performances of the TiO 2 pillared montmorillonite [J], Journal of Hazardous Materials,2012, 235–236, 186–193, http://dx.doi.org/10.1016/j.jhazmat.2012.07.038 Hassan Ouachtak AE, Guerdaoui RH, Akhouairi S, Haouti RE, Hafid N, Addi AA, Šljukic´ B, Diogo MF, Santos (2021) Mohamed Labd Taha, Highly efficient and fast batch adsorption of orange G dye from polluted water using superb organo-montmorillonite: Experimental study and molecular dynamics investigation. J Mol Liq 335:116560. https://doi.org/10.1016/j.matchemphys.2020.124125 Hongjuan S, Peng T, Liu B, Xian H (2015) Effects of montmorillonite on phase transition and size of TiO 2 nanoparticles in TiO 2 /montmorillonite nanocomposites [J]. Appl Clay Sci 114:440–446,. http://dx.doi.org/10.1016/j.clay.2015.06.026 Hongjuan S, Peng T, Liu B (2015) Haiyang Xian,Effects of montmorillonite on phase transition and size of TiO 2 nanoparticles in TiO 2 /montmorillonite nanocomposites [J]. Appl Clay Sci 114:440–446. http://dx.doi.org/10.1016/j.clay.2015.06.026 0169–1317 Mogyoro´si K, Dékány I, Fendler JH, Preparation and Characterization of Clay Mineral Intercalated Titanium Dioxide Nanoparticles[J], Langmuir 2003, 19, 2938–2946, https://doi.org/10.1021/la025969a Chen K, Li J, Wang W, Zhang Y, Wang X, Su H (2011) The preparation of vanadium-doped TiO 2 –montmorillonite nanocomposites and the photodegradation of sulforhodamine B under visible light irradiation [J]. Appl Surf Sci 257:7276–7285. doi: 10.1016/j.apsusc.2011.03.104 Lingeswarran Muniandy F, Adam AR, Mohamed E-P, Ng (2014) The synthesis and characterization of high purity mixed microporous/ mesoporous activated carbon from rice husk using chemical activation with NaOH and KOH [J]. Microporous Mesoporous Mater 197:316–323. http://dx.doi.org/10.1016/j.micromeso.2014.06.020 Lila Djouadi H, Khalaf HB, Boutoumi H, Kezzime A, Arturo Santaballa J, Canle M (2018) Degradation of aqueous ketoprofen by heterogeneous photocatalysis using Bi 2 S 3 /TiO 2 –Montmorillonite nanocomposites under simulated solar irradiation [J]. Appl Clay Sci 166:27–37. https://doi.org/10.1016/j.clay.2018.09.008 Yuan L, Huang D, Guo W, Yang Q, Yu J, TiO2/montmorillonite nanocomposite for removal of organic pollutant [J], Appl Clay Sci, 2011, 53, 272–278. doi: 10.1016/j.clay.2011.03.013 Ping Zhang Z, Mo L, Han X, Zhu B, Wang C, Zhang, Preparation and Photocatalytic Performance of Magnetic TiO 2 /Montmorillonite/Fe 3 O 4 Nanocomposites [J], Ind Eng Chem Res 2014, 53, 8057–8061, http: //dx.doi.org/10.1021/ie5001696 Paulina Górska A, Zaleska J, Hupka (2009) Photodegradation of phenol by UV/TiO 2 and Vis/N, C-TiO 2 processes: Comparative mechanistic and kinetic studies [J]. Sep Purif Technol 68:90–96. https://doi.org/10.1016/j.seppur.2009.04.012 Ruikun Wang Q, Ma Z, Zhao X, Ye Q, Jin, Zhenghui Zhao,Ji Liu, Adsorption of Surfactants on Coal Surfaces in the Coking Wastewater Environment: Kinetics and Effects on the Slurrying Properties of Coking Wastewater–Coal Slurry [J], Ind Eng Chem Res 2019, 58, 28, 12825–12834, https://doi.org/10.1021/acs.iecr.9b01829 Djellabi R, Ghorab MF, Cerrato G, Morandi S, Gatto S, Oldani V, Di Michele A, Bianchi CL (2014) Photoactive TiO 2 –montmorillonite composite for degradation of organic dyes in water [J]. J Photochem Photobiol A 295:57–63. https://doi.org/10.1016/j.jphotochem.2014.08.017 Parayil SK, Kibombo HS, Wu C-M, Peng R, Jonas Baltrusaitis b, Ranjit T. Koodali. Enhanced photocatalytic water splitting activity of carbon-modified TiO 2 composite materials synthesized by a green synthetic approach [J]. Int J Hydrogen Energy, 2012, 37, 8257–8267. https://doi.org/10.1016 /j.ijhydene.2012.02.067 Shivatharsiny Rasalingama HS, Kibombo C-M, Wu R, Peng J, Baltrusaitis, Ranjit T, Koodali. Competitive role of structural properties of titania–silica mixed oxides and a mechanistic study of the photocatalytic degradation of phenol [J]. Appl Catal B, 2014, 148–149, 394–405, http://dx.doi.org/10.1016/j.apcatb.2013.11.025 Makrigianni V, Giannakas A, Daikopoulos C, Deligiannakis Y, I. Konstantinou, Prepara tion, characterization and photocatalytic performance of pyrolytic-tire-char/TiO 2 composites, toward phenol oxidation in aqueous solutions, Applied Catalysis B: Environmental, 2015, 174, 244–252, http://dx.doi.org/10.1016/j.apcatb.2015.03.007 Wang X, Huang S, Zhu L, Tian X, Li S, Tang H, Correlation between the adsorption ability and reduction degree of graphene oxide and tuning of adsorption of phenolic compounds [J] (2014) Carbon 69:101–112. http://dx.doi.org/10.1016/j.carbon.2013.11.070 Liu YX, Zhang X, Guo L, Wu F (2008) N. S. Deng,Photodegradation of Bisphenol A in the Montmorillonite KSF Suspended Solutions [J],Ind. Eng Chem Res 47:7141–7146. https://doi.org/10.1021/ie800169c Tables Table 1 is not available with this version. Supplementary Files GraphicalAbstract.doc Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 18 Jan, 2022 Reviewers invited by journal 22 Sep, 2021 Editor invited by journal 15 Sep, 2021 First submitted to journal 25 Aug, 2021 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-848926","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":53785338,"identity":"67d08602-e206-4506-ad63-b8bf641eceeb","order_by":0,"name":"Huijuan 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1","display":"","copyAsset":false,"role":"figure","size":1442505,"visible":true,"origin":"","legend":"XRD patterns of 30%TiO2/MMT calcined at different temperatures a MMT b 400℃-30%TiO2/MMT c 500℃-30%TiO2/MMT d 600℃-30%TiO2/MMT \ne 700℃-TiO2/MMT f 600℃-TiO2\n","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/00c4e1c66f9bb10c85c9c7f6.png"},{"id":14022706,"identity":"99848b30-bca8-4b90-95e4-4a12f811b77f","added_by":"auto","created_at":"2021-09-27 15:24:22","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":158073,"visible":true,"origin":"","legend":"Shows SEM images of raw montmorillonite (a) and TEM images of pure TiO2 \n(b) and 30% TiO2/MMT (c) composites calcined at 600℃ for 4h\n","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/d77fbe9f15c701e8677c9cf6.png"},{"id":14022355,"identity":"2170acb9-8d54-49be-85ac-52a81b8ff9dc","added_by":"auto","created_at":"2021-09-27 15:21:22","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1163025,"visible":true,"origin":"","legend":"Infrared spectra of each catalyst and composite ：a 110-TiO2 b 110-MMT c 110-30TiO2 d 600-TiO2 e 600-MMT f 600-30-TiO2-MMT (a) IR spectra of 30% TiO2/MMT Composite (b) IR spectra of 30% TiO2/MMT at different temperatures: a 700℃ b 600℃ c 500℃ d 400℃ e 300℃","description":"","filename":"fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/f3102910eff6968865163e2e.png"},{"id":14022354,"identity":"60f7a83b-c369-49e7-b65c-cff233cacd48","added_by":"auto","created_at":"2021-09-27 15:21:22","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":575661,"visible":true,"origin":"","legend":"Diffuse reflectance UV-Vis spectra of different sample ","description":"","filename":"fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/05004d03c3ae0afbab98b802.png"},{"id":14022705,"identity":"78b3dbbd-5e6e-4699-9662-db6f7dbe53ba","added_by":"auto","created_at":"2021-09-27 15:24:22","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":719917,"visible":true,"origin":"","legend":"Phenol photocatalytic degradation over different photocatalysts calcined at different temperatures","description":"","filename":"fig5.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/32fdc5608dfededd0a41581a.png"},{"id":14022707,"identity":"fcc44be7-1715-4363-af33-d44cf0ddd5e7","added_by":"auto","created_at":"2021-09-27 15:24:22","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":458294,"visible":true,"origin":"","legend":"Phenol photocatalytic degradation rate over 30%TiO2/MMT composites calcined at different temperatures","description":"","filename":"fig6.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/3328fa5390cf117b49ea9d82.png"},{"id":14022347,"identity":"36a8cb82-c936-43a6-a15b-fc26259049a6","added_by":"auto","created_at":"2021-09-27 15:21:22","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":452586,"visible":true,"origin":"","legend":"Phenol degradation activity of 30% TiO2/MMT composites in different pH reaction solutions","description":"","filename":"fig7.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/4162235a3ac5962b1b267f79.png"},{"id":14022352,"identity":"88c4b441-3ede-478f-95c4-ff1fda14a702","added_by":"auto","created_at":"2021-09-27 15:21:22","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":410926,"visible":true,"origin":"","legend":"Phenol degradation activity of 30% TiO2/MMT photocatalytic composites with different dosages","description":"","filename":"fig8.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/d7bed6ea7d5b6eba7352f0d0.png"},{"id":14022357,"identity":"85c315e2-4176-4c59-a20c-818bf80c6e46","added_by":"auto","created_at":"2021-09-27 15:21:22","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":973823,"visible":true,"origin":"","legend":"HPLC chromatograms recorded during phenol decomposition under UV light on\n (a) TiO2 and (b) 30%TiO2/MMT photocatalysts\n","description":"","filename":"fig9.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/036f85d17651ed83787d52c2.png"},{"id":14022351,"identity":"7263ab5b-1309-4567-a390-f836cae9d2c2","added_by":"auto","created_at":"2021-09-27 15:21:22","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":227871,"visible":true,"origin":"","legend":"Possible reaction routes for phenol degradation over TiO2/MMT composites","description":"","filename":"fig10.png","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/3235b4183ee0056b60ea307c.png"},{"id":15675284,"identity":"e8c81df2-9b35-4799-b822-108de8d19777","added_by":"auto","created_at":"2021-11-18 14:27:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1985408,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/5086ca09-f4ea-4ee3-b615-a57e59aa7cc4.pdf"},{"id":14022348,"identity":"331fa9bd-c261-4d81-866c-68af217dd337","added_by":"auto","created_at":"2021-09-27 15:21:22","extension":"doc","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1217536,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.doc","url":"https://assets-eu.researchsquare.com/files/rs-848926/v1/d7d88cf3cb1a2d1019fbe755.doc"}],"financialInterests":"","formattedTitle":"\u003cp\u003eDegradation of Phenol by Photocatalysis Using TiO\u003csub\u003e2\u003c/sub\u003e/Montmorillonite Composites Under UV Light\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePhenol and its derived compounds are one of the most toxic, and are used widely in petrochemical, chemical, and pharmaceutical industries. When they enter into the natural waters will cause serious pollution and great harm to environment. Drinking water containing phenols may cause severe renal insufficiency, convulsions, and even death (Ruikun Wang 2019). Phenol degradation techniques include adsorption, extraction, electrolysis and photocatalytic oxidation (Lingeswarran Muniandy 2014). Among them, TiO\u003csub\u003e2\u003c/sub\u003e-based catalysts can handle with higher concentrations of phenol-containing wastewater, mild reaction conditions, high treatment efficiency and no secondary pollution, and is widely used as photoelectric conversion, photochemical synthesis, and photocatalytic oxidation of environmental pollutants (Paulina G\u0026oacute;rska 2009; Ali Gundogdu et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). However, poor adsorption, narrow absorption spectrum and difficult recovery of nanoparticles of TiO\u003csub\u003e2\u003c/sub\u003e limit its application in water treatment (Sreenivasan Koliyat Parayil 2012).\u003c/p\u003e\n\u003cp\u003eMontmorillonite (MMT) is a layered aluminosilicate mineral, its theoretical molecular formula is N\u003csup\u003ez+\u003c/sup\u003e\u003csub\u003e\u0026chi;/z\u003c/sub\u003eM\u003csub\u003e6\u003c/sub\u003e\u003csup\u003e2+\u003c/sup\u003e[Si\u003csub\u003e8\u0026thinsp;\u0026minus;\u0026thinsp;\u0026chi;\u003c/sub\u003eAl\u003csub\u003e\u0026chi;\u003c/sub\u003e]O\u003csub\u003e20\u003c/sub\u003e(OH)\u003csub\u003e4\u003c/sub\u003e\u0026middot;nH\u003csub\u003e2\u003c/sub\u003eO. The unit is composed of two layers of silicon-oxygen tetrahedron with a layer of aluminum-oxygen octahedron. It belongs to a 2:1 type structure with swellable hydrous aluminosilicate. The special crystal structure makes montmorillonite have ion exchange capacity and dispersion suspension stability. It possesses layered structures, larger interlayer distance, specific surface area and thermal stability, which can be obtained through physical and chemical methods such as pillaring, insertion replacement and ion exchange (Hassan Ouachtak 2021). Y. X. Liu studied the commercially available montmorillonite KSF as photoactive reagent and utilized for BPA photodegradation, and found that the BPA degradation increased with the concentration of clays in the range of 0.5 g/L to 5 g/L. The photodegradation rate of BPA is fitted well into the Langmuir-Hinshelwood equation (Y. X. Liu 2008). K. Mogyor\u0026oacute;si et al prepared clay mineral intercalated TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles, and found that calcination was not necessary for nanocomposites preparation that had high specific surface areas and well-crystallized anatase contents and thus could be used as an efficient photocatalyst(K. Mogyoro\u0026acute;si 2003). Daimei Chen et al. synthesized TiO\u003csub\u003e2\u003c/sub\u003e pillared montmorillonite and investigated as methylene blue photocatalytic activity, the prepared TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites exhibited superior photocatalyic property and the maximum removal efficiency was up to 98% within 90 min (Daimei Chen 2012).\u003c/p\u003e\n\u003cp\u003eIn this paper, TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites were prepared by a sol-gel method. The phenol solution was used as model degradation molecular. The effects of TiO\u003csub\u003e2\u003c/sub\u003e loading amount, calcination temperature and solution pH on the degradation of phenol by TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites were investigated. FTIR, XRD and SEM techniques were used to characterize the prepared composites.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cdiv class=\"Section2\" id=\"Sec2\"\u003e\n \u003ch2\u003e1.1. Materials\u003c/h2\u003e\n \u003cp\u003eThe montmorillonite (MMT) was supplied from Xinghe County, Inner Mongolia, China (purity 85%, the major compositions is: SiO\u003csub\u003e2\u003c/sub\u003e, 78%; Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e ,11.63%; MgO, 3.71%; Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, 2.81% and CaO is 2.03%). (C\u003csub\u003e4\u003c/sub\u003eH\u003csub\u003e9\u003c/sub\u003eO) \u003csub\u003e4\u003c/sub\u003eTi, (CR, Sinopharm Chemical Reagent (Shanghai) Co., Ltd .; The components of MMT are shown in Table.1; Phenol, AR, Chengdu Kelong Chemical Reagent Factory; Sodium Chloride, AR, Chengdu Kelong Chemical Reagent Factory; 4-Aminoantipyrine, CR, Shanghai Qiangshun Chemical Reagent Co., Ltd.; Potassium ferricyanide, CR, Shanghai Qiangshun Chemical Reagent Co., Ltd .;\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec3\"\u003e\n \u003ch2\u003e1.2 Sample preparation\u003c/h2\u003e\n \u003cp\u003e(1) Modification of montmorillonite (MMT)\u003c/p\u003e\n \u003cp\u003eMontmorillonite (Ca-MMT, 100g) was dispersed into 1000 mL 1.0 mol/L NaCl solution, and stirred for 2 h at 60℃ water bath. Then, the resulting suspension was separated by centrifugation and washed with distilled water until no Cl\u003csup\u003e-\u003c/sup\u003e (using 0.1 mol/L AgNO\u003csub\u003e3\u003c/sub\u003e test), dried at 110℃ for 24 h, ground, sodium montmorillonite (Na-MMT) can be obtained after 100 mesh.\u003c/p\u003e\n \u003cp\u003e(2) Preparation of TiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e was synthesized through sol-gel method. 5 mL Tetrabutyl titanate was dissolved in 7 mL anhydrous ethanol under vigorous stirring. At the same time, the above solution was dropwise added to a mixture with 15 mL ethanol, 8 mL deionized water and 2 mL acetic acid to make a solution. Under vigorously stirring conditions, the viscosity of the mixed solution turns more and more and then changed into a sol. The product was aged for 24 h, dried at 110 ℃ for 24h and finally at different temperature for 4h.\u003c/p\u003e\n \u003cp\u003e(3) Preparation of TiO\u003csub\u003e2\u003c/sub\u003e/MMT\u003c/p\u003e\n \u003cp\u003eThe TiO\u003csub\u003e2\u003c/sub\u003e sol was mixed with a certain percent of modified Na-MMT aqueous suspension. In this mixed suspension. The beaker was rinsed with absolute ethanol and thoroughly stirred to prepare TiO\u003csub\u003e2\u003c/sub\u003e/MMT. Aging for 24h, the sol was dried at 110℃ for 24 h, and then placed in a muffle furnace (Shanghai Chongming Experimental Instrument Factory) and calcined at a certain temperature (300\u0026ndash;600℃) for 4 h, a modified TiO\u003csub\u003e2\u003c/sub\u003e/MMT is obtained (named as TiO\u003csub\u003e2\u003c/sub\u003e/MMT, which is the mass percentage of TiO\u003csub\u003e2\u003c/sub\u003e and MMT, such as 40% TiO\u003csub\u003e2\u003c/sub\u003e/MMT means that the TiO\u003csub\u003e2\u003c/sub\u003e mass is 0.4 and the MMT mass is 1.00).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec4\"\u003e\n \u003ch2\u003e1.3 Characterization\u003c/h2\u003e\n \u003cp\u003eThe as-prepared samples were characterized by different techniques. The crystalline phases of the TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites were investigated with X-ray diffraction (XRD, Rigaku D/Max 2000, Cu K\u0026alpha; radiation source with wavelength of \u0026lambda;\u0026thinsp;=\u0026thinsp;0.15418 at 40 kV and 30 mA). The Fourier transform infrared (FT-IR) spectra were recorded on a Spectrum 100 spectrometer (BRUKER TENSOR27). Transmission electron microscopy (TEM, JEOL LEM-100CXII) and scanning electron microscope (SEM, S-3000N, Hitachi, Japan) was used to observe the microstructure of as-prepared composites. Using BaSO\u003csub\u003e4\u003c/sub\u003e as the reflectance sample, the UV\u0026ndash;vis diffuse reflectance spectra were recorded with a HITACHI U-3010 spectrometer.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec5\"\u003e\n \u003ch2\u003e1.4 Photocatalytic degradation of phenol\u003c/h2\u003e\n \u003cp\u003eThe photocatalytic activities of the produced TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites were measured by degrading phenol. In each experiment, 0.2 g photocatalyst was added to 100 mL solution (10 mg/L, the initial pH is 6, if the pH needs change, adjust with acetic acid and ammonia). of the pollutants and stirred in dark for 30 min in order to reach an adsorption-desorption equilibrium. Then, the suspension was irradiated with a UV light source (300 W, Optima wavelength 365 nm). During the irradiation period, an aliquot of 2.0 mL suspension was collected at regular 30 min intervals, centrifuged to remove the photocatalyst, the aliquots were immediately centrifuged and analyzed using UV\u0026ndash;vis spectrometer (UV-1800, Shimadzu).\u003c/p\u003e\n \u003cp\u003eIn order to quantify the evolution of intermediate products, the extinction coefficients of maleic acid (MA), fumaric acid (FA), hydroquinone (HQ), catechol (CC), benzoquinone (BQ), and phenol (PhOH) were measured independently. The concentrations of phenolic compounds were calculated using high performance liquid chromatography (HPLC, PerkinElmer Altus 30) equipped with a Sinochrom ODS-BP column (3.5 \u0026micro;m; 4.6\u0026times;250 mm) and a 220/240 pump, and also equipped with a Spectra 100 UV\u0026ndash;Vis detector to identify the degradation products as an evaluation of the photocatalytic activity of the synthesized TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites. A mobile phase composition of methanol / NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e (with 0.5 mol/L) ratio was 70:30. The mobile phase was delivered at a flow rate of 1.0 mL /min and the detection wavelength was set at 254 nm. The 10 uL solutions were filtered on a 0.45 \u0026micro;m cellulosic filter before injected into the HPLC chromatography.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results And Discussion","content":"\u003cdiv class=\"Section2\" id=\"Sec7\"\u003e\n \u003ch2\u003e2.1 XRD results\u003csub\u003e2\u003c/sub\u003e\u003c/h2\u003e\n \u003cp\u003eThe XRD pattern of the as-prepared pure MMT, TiO\u003csub\u003e2\u003c/sub\u003e and 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT catalysts are shown in Fig.\u0026nbsp;1. For pure montmorillonite, the diffraction peak at 2\u0026theta;\u0026thinsp;=\u0026thinsp;19.77\u0026deg;,21.85\u0026deg; and 26.76\u0026deg; attribute to the Si-O-Si diffraction peak of Na-montmorillonite, the Si-O-Al and the (101) of quartz, respectively. The original montmorillonite sample (MMT) shows a series of reflections at 2\u0026theta;\u0026thinsp;=\u0026thinsp;18.64\u0026deg; with d003\u0026thinsp;=\u0026thinsp;0.448 nm and 2\u0026theta;\u0026thinsp;=\u0026thinsp;19.77\u0026deg; with d100\u0026thinsp;=\u0026thinsp;0.449 nm, respectively. According to the JCPDS card (NO. 00-003-0010), it is corresponding to Na-montmorillonite (Hongjuan Sun 2015). The diffraction peaks of TiO\u003csub\u003e2\u003c/sub\u003e at 2\u0026theta;\u0026thinsp;=\u0026thinsp;25.2\u0026deg;, 38.1\u0026deg;, 47.7\u0026deg; and 54.4\u0026deg; correspond to those of anatase (101), (004), (105) and (204), respectively. At the same time, there is a rutile characteristic diffraction peak (2\u0026theta;\u0026thinsp;=\u0026thinsp;27.43\u0026deg;) for pure TiO\u003csub\u003e2\u003c/sub\u003e(600 ℃, 4 h) and 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT (700 ℃, 4 h) which suggests that the montmorillonite as a carrier can increase TiO\u003csub\u003e2\u003c/sub\u003e phase transition temperature, and make it still anatase phase after calcined at 600 ℃. The positions of the characteristic diffraction peaks of montmorillonite in the 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composite calcined at different temperatures has no obvious change, and the peak strength is weaker. It can be seen that the introduction of TiO\u003csub\u003e2\u003c/sub\u003e do not change the structure of montmorillonite. The diffraction peaks of TiO\u003csub\u003e2\u003c/sub\u003e/MMT at 2\u0026theta;\u0026thinsp;=\u0026thinsp;26.76\u0026deg; and 31.02\u0026deg; are obviously weakened or even disappeared compared with the original montmorillonite, which indicates that the original Si-O-Al bond was destroyed, and a new Si-O-Ti bond is constructed after replaced the aluminum ion in the interlayer (Lila Djouadi 2018). The average crystal size of the particles can be estimated from the widths of TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites reflections by using the Scherrer formula, d\u0026thinsp;=\u0026thinsp;0.89\u0026middot;\u0026lambda;/(\u0026beta;\u0026middot;cos\u0026theta;), where \u0026lambda; (1.5413 \u0026Aring;) is the wavelength, \u0026theta; is the Bragg angle (\u0026deg;), d is the average crystallite size (nm) and \u0026beta; is the full width at half-maximum. The calculated data of the five TiO\u003csub\u003e2\u003c/sub\u003e-based catalysts are followed in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable border=\"1\" id=\"Tab1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCrystalline size of TiO\u003csub\u003e2\u003c/sub\u003e in different samples\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ed/nm\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTiO\u003csub\u003e2\u003c/sub\u003e(600℃,4h)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22.51\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT (400℃,4h)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.61\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT (500℃,4h)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.68\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT (600℃,4h)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.66\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT (700℃,4h)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e29.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eIt can be seen from Table.2, The grain size of TiO\u003csub\u003e2\u003c/sub\u003e reduces from 22.51 nm to 10.66 nm for pure TiO\u003csub\u003e2\u003c/sub\u003e and 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT calcined at 600℃ for 4h, indicating that the particle size of TiO\u003csub\u003e2\u003c/sub\u003e pillared montmorillonite decreased effectively. And the crystalline size of TiO\u003csub\u003e2\u003c/sub\u003e in 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites calcined at different temperatures also gradually increased with the temperature.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec8\"\u003e\n \u003ch2\u003e2.2 SEM and TEM\u003c/h2\u003e\n \u003cp\u003eFigure 2 shows SEM images of raw montmorillonite (a) and TEM images of pure TiO\u003csub\u003e2\u003c/sub\u003e (b) and 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT (c) composites calcined at 600 ℃ for 4h. The raw montmorillonite shows larger particle aggregates with a flower-like layer structure, the flaky structure is relatively close. For the pure TiO\u003csub\u003e2\u003c/sub\u003e, the particles is relatively uniform, with some agglomeration, which may be related to the higher calcination temperature, the particle size is about 19 nm. For the 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT (600℃, 4h) composite, it can be observed the larger platelets and layer structure of montmorillonite clearly. Since the TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles were intercalated, the layer space was enlarged and the structural layers of montmorillonite were separated (R. Djellabi 2014 ). Although the montmorillonite layers were still largely parallel, they lost long-range order in the c direction after TiO\u003csub\u003e2\u003c/sub\u003e intercalation. Which is consistent with the disappearance of the (001) reflection in the XRD patterns(Ping Zhang 2009). The lattice fringe image of the original montmorillonite sample shows that the structural layers are orderly with a layer space of 2.84 nm. And there are a lot of small aggregates, which are probably broken platelets and agglomerates of TiO\u003csub\u003e2\u003c/sub\u003e crystallites caused by the hydrolysis of surface Ti(OC\u003csub\u003e4\u003c/sub\u003eH\u003csub\u003e9\u003c/sub\u003e)\u003csub\u003e4\u003c/sub\u003e (Boualem Damardji 2008). TiO\u003csub\u003e2\u003c/sub\u003e particle size is about 10 nm by calculation, which is consistent with the data calculated by Scherrer formula in XRD. At the same time, TiO\u003csub\u003e2\u003c/sub\u003e pillared montmorillonite decreases its particle size from 19 nm to 10 nm, while the layered structure of montmorillonite remains unchanged, which also make TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites keep good adsorption efficiency of montmorillonite, and then enhance the phenol degradation activity of TiO\u003csub\u003e2\u003c/sub\u003e/MMT.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec9\"\u003e\n \u003ch2\u003e2.3 FT-IR characterization\u003c/h2\u003e\n \u003cp\u003eFigure\u0026nbsp;3 presents FT-IR spectra of different samples of TiO\u003csub\u003e2\u003c/sub\u003e, MMT and TiO\u003csub\u003e2\u003c/sub\u003e/MMT dried at 110℃ and calcined at 600 ℃ for 4h, respectively. For the purified MMT, the broad band at 3422 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is due to the stretching vibration of the hydroxyl group and the interlayer water molecules. And the weak peak at 3624 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to -OH stretching vibration of Al-O-H. Bands at 1645 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1468 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are caused by the bending vibration of the hydroxyl group and the interlayer water molecules. The vibration peak at 1079 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is caused by the antisymmetric stretching vibration of Si-O-Si in montmorillonite, which caused by the strong hydration of Ca, Mg and Al plasma strengthens the hydrogen bond between the surface of montmorillonite layer and water, weakens and disappears the band of Si-O bond, resulting in the changing of Si-O and Si-O-Si into a single peak (Ke Chen 2001). Bands at 845 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 794 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attribute to the bending vibration peak of Mg\u003csup\u003e2+\u003c/sup\u003e-OH and the hydroxyl vibration of MgAl-OH, respectively. And also bands at 521 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 474 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 916 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are suggested to the bending vibration of Si-O-Al, Si-O-Si and octahedral Al-O(OH)-Al in montmorillonite independently. The broad peak at 587 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to Ti-O bond vibration, which indicates that TiO\u003csub\u003e2\u003c/sub\u003e is amorphous. After TiO\u003csub\u003e2\u003c/sub\u003e modified MMT, interlayer water and hydroxyl increased, which restricted the vibration of structural hydroxyl Al-OH. The peak at 3621 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e lost, and the two peaks at 1021 and 917 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appeared, it shows that the composition of the interlayer of montmorillonite changed after TiO\u003csub\u003e2\u003c/sub\u003e was introduced, and the in-plane stretching vibration peaks of Ti-O-C and Si-O-Si generated (Lingling Yuan 2011; Chihiro Ooka et al. \u003cspan class=\"CitationRef\"\u003e2003\u003c/span\u003e ). Also at 796 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the absorption of the hydroxyl vibration peak of MgAl-OH weakened, which may be related to the removal of hydroxyl as octahedron Ti hydrated ions into the interlayer. At the same time, the strength of 521 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peak in the composite is obviously weakened and widened, which is the superposition of Ti-O and Si-O absorption peaks.\u003c/p\u003e\n \u003cp\u003eThe results show that the strength of Si-O bond is also affected by titanium in lay. For the 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT calcined at 600℃ for 2h, 3422 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 916 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e disappear, while 1468 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peak strength decreases, indicating that interlayer water lost. The vibration peak of Ti-O becomes narrow at 600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, indicating the TiO\u003csub\u003e2\u003c/sub\u003e crystal phase formed. At the same time, the 1070 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peak of 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT changed into a single peak, which seems that the basic framework of MMT remained unchanged and remained the original structure. For the 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT calcined at different temperatures, it can be seen that the peaks at 3625 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1030 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 845 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e gradually disappear, and the peaks of 3431 and 1648 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e gradually decrease, which is caused by the evaporation of interlayer water (V. Makrigianni 2015).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec10\"\u003e\n \u003ch2\u003e2.4 UV-ViS\u003c/h2\u003e\n \u003cp\u003eFigure\u0026nbsp;4 shows diffuse reflectance UV-Vis spectra of 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT calcined from 400\u0026ndash;700℃. It can be seen from the Fig.\u0026nbsp;4 that the absorption band of pure TiO\u003csub\u003e2\u003c/sub\u003e at 200\u0026ndash;400 nm belongs to the electron coordinated by the titanium coordinated oxygen atom to the empty orbit of the central titanium atom, the characteristic absorption formed by OB\u003csub\u003e2p\u003c/sub\u003e\u0026rarr;TiB\u003csub\u003e3dB\u003c/sub\u003e charge transfer, in which the tetrahedron at 248 nm. The characteristic peak of coordination titanium, the absorption peak around 337 nm was the absorption peak of octahedral coordination titanium(Aydin Hassani 2015). The peaks of 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites calcined at different temperatures around 433 and 504 nm are Fe-O absorption peaks of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, because of the used montmorillonite content of 2.8% Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. At the same time, 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites calcined at different temperatures have a strong light absorption performance. The value Eg was deliberate from the UV\u0026ndash;visible pattern of the titled TiO\u003csub\u003e2\u003c/sub\u003e/MMT by extrapolating the line through the k axis and it is exposed in Fig.\u0026nbsp;4. The wavelength maxima had 409.6 nm (pure TiO\u003csub\u003e2\u003c/sub\u003e), 427.1 nm (30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT, 400℃), 434.7 nm (30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT, 500℃), 418.4nm (30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT, 600℃), and 451.5nm (30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT, 700℃), respectively. Since the photoabsorption performance of the photocatalyst is positively related to the photocatalytic degradation activity of phenol, it was confirmed that the 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT(600℃,2h) prepared by the sol-gel method has the best photocatalytic activity for phenol degradation.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec11\"\u003e\n \u003ch2\u003e2.5 Photocatalytic activity\u003c/h2\u003e\n \u003cdiv class=\"Section3\" id=\"Sec12\"\u003e\n \u003ch2\u003e2.5.1 Effect of TiO\u003csub\u003e2\u003c/sub\u003e loading amount on TiO\u003csub\u003e2\u003c/sub\u003e/MMT\u003c/h2\u003e\n \u003cp\u003eFigure\u0026nbsp;5 shows the phenol removal efficiency under UV light over MMT, TiO\u003csub\u003e2\u003c/sub\u003e and different loading of TiO\u003csub\u003e2\u003c/sub\u003e on TiO\u003csub\u003e2\u003c/sub\u003e/MMT calcined at 600℃ for 4h. The results showed that the photolysis of phenol in the absence of photocatalyst is only 1.5%, which can be neglected. And the phenol degradation is 11.5% over MMT which shows that MMT has a certain adsorption capacity for phenol solution, but the adsorption activity was very low. It has 58.5% photocatalysis activity over pure TiO\u003csub\u003e2\u003c/sub\u003e. Also, for different amount loading of TiO\u003csub\u003e2\u003c/sub\u003e/MMT, the results indicated that the photo degradation efficiency of phenol increased with TiO\u003csub\u003e2\u003c/sub\u003e content until 30%TiO\u003csub\u003e2\u003c/sub\u003e, then decreased after more TiO\u003csub\u003e2\u003c/sub\u003e loading. Because TiO\u003csub\u003e2\u003c/sub\u003e was the active center of the photocatalytic reaction, when its loading is less, the phenol degradation is low. When the loading of TiO\u003csub\u003e2\u003c/sub\u003e was overdose, photo-generated electrons and holes were generated under light conditions, and the photo-generated electrons and holes recombine to form a composite band, which affects the formation of hydroxyl active groups, reduces the utilization of ultraviolet light, causes degradation efficiency reduced. It was concluded that the photocatalytic activity of 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites has the best phenol degradation performance under ultraviolet light.\u003c/p\u003e\n \u003cp\u003eTheoretically, the adsorption and degradation activity of TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites on phenol was the sum of the phenol adsorption on montmorillonite and photodegradation over pure TiO\u003csub\u003e2\u003c/sub\u003e. However, it can be seen from the Fig.\u0026nbsp;5, the phenol adsorption rate of montmorillonite to 11.5% and the degradation rate of TiO\u003csub\u003e2\u003c/sub\u003e was 58.8% after 240 minutes under UV light, the sum of the two was only 70.3%, which is significantly lower than the 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composite (89.75%). On the one hand, the loading of montmorillonite may increase the crystalline phase transition temperature of TiO\u003csub\u003e2\u003c/sub\u003e to a certain extent; it still maintains the anatase phase structure at 600℃. And also increases the degree of TiO\u003csub\u003e2\u003c/sub\u003e dispersion and makes its particles smaller, which contributed to improving the phenol degradation over TiO\u003csub\u003e2\u003c/sub\u003e /MMT composites(Hongjuan Sun 2015).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"Section3\" id=\"Sec13\"\u003e\n \u003ch2\u003e2.4.2 Effect of calcined temperature\u003c/h2\u003e\n \u003cp\u003eFigure\u0026nbsp;6 shows the phenol photocatalytic degradation over 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites calcined at different temperatures (from 300 to 700℃). For the 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites calcined from 300℃ to 600℃, it can be seen that the degradation rate gradually increased with roasting temperature. When calcined at 600℃, the phenol degradation rate reached 89.75%, but is only 15.08% when the roasting temperature is 700℃, decreased significantly. Therefore, in this catalytic reaction system, the optimal calcination temperature of 30% TiO\u003csub\u003e2\u003c/sub\u003e /MMT photocatalytic composite is 600℃.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"Section3\" id=\"Sec14\"\u003e\n \u003ch2\u003e2.5.2 The effect of the initial pH\u003c/h2\u003e\n \u003cp\u003eThe solution pH is one of the important parameters that can markedly affect the photocatalytic process. In the present work, the effect of the initial pH on the phenol photocatalytic degradation efficiency was studied in the pH range of 2\u0026ndash;12 (Fig.\u0026nbsp;7). In this experiment, acetic acid and ammonia are usually used to adjust the pH value of the solution. The results indicated that the degree of photodegradation efficiency increased with the pH values from 2 to 6 and then decreased. It can be seen from Fig.\u0026nbsp;7 that the photocatalytic performance of the reaction solution under slightly acidic conditions was significantly higher than that obtained under slightly alkaline conditions, the pH value will change the interfacial charge of the TiO\u003csub\u003e2\u003c/sub\u003e/MMT, thereby changing the dispersion of the particles in the solution, and affecting the adsorption behavior of the montmorillonite matrix on the catalyst surface. In the photocatalyst reaction, the electrons were excited from the valence band to the conduction band, forming electrons (e\u003csup\u003e\u0026minus;\u003c/sup\u003e) and holes (h\u003csup\u003e+\u003c/sup\u003e). The highly active holes consume OH\u003csup\u003e\u0026minus;\u003c/sup\u003e in water during the reaction and oxidize them to have strong oxidative active๒OH, then e\u003csup\u003e\u0026minus;\u003c/sup\u003e and h\u003csup\u003e+\u003c/sup\u003e undergo redox reactions with substances dispersed in water; As the pH value increases, the concentration of OH\u003csup\u003e\u0026minus;\u003c/sup\u003e in the solution sharply increases, then the concentration of \u0026middot; OH increased significantly, the conduction electrons reacted with the adsorbed O\u003csub\u003e2\u003c/sub\u003e to form O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e, which could also generate \u0026middot; OH with H\u003csub\u003e2\u003c/sub\u003eO, so the degradation efficiency increased with the pH value. However, too high a concentration of \u0026middot; OH will cause a decrease in photocatalytic activity (Chunquan Li 2021). Therefore, the photocatalytic effect was better under suitable pH conditions, which has a high photocatalytic degradation rate under acidic conditions.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"Section3\" id=\"Sec15\"\u003e\n \u003ch2\u003e2.5.2 The effect of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT (600℃,4h) dosage\u003c/h2\u003e\n \u003cp\u003eCatalyst dosage is an important parameter in heterogeneous photocatalytic reaction. In order to determine the effect of catalyst dosage on the phenol photodegradation, experiments were carried out by varying the amount of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT from 0.1 to 0.4 g (Fig.\u0026nbsp;8). Increasing the amount of photocatalyst from 0.1 g to 0.2 g resulted in increasing the photodegradation efficiency from 42.25\u0026ndash;89.96% at the reaction time of 240 min, respectively. By adding the catalyst dosage, promoted the production of reactive species. However, more catalyst dosage would also induce greater aggregation of the catalysts and added the turbidity of the solution, reduce the degree of light penetration through the solution and thereby leading to a reduction in the phenol degradation efficiency. Therefore, 0.2 g 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT photocatalysts is the best amount for phenol photocatalytic reaction(Shivatharsiny Rasalingama 2014).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"Section3\" id=\"Sec16\"\u003e\n \u003ch2\u003e2.5.3 High performance liquid chromatography -(HPLC) analysis\u003c/h2\u003e\n \u003cp\u003eHPLC was employed to identify the degradation products in order to evaluate the catalytic activities over the pure TiO\u003csub\u003e2\u003c/sub\u003e (600\u0026deg;C, 4 h) and 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT (600\u0026deg;C, 4 h) photocatalysts. Under our experimental conditions, benzoquinone (BQ), hydroquinone (HQ), maleic acid (MA), and fumaric acid (FA) have been identified as intermediates. It should be noted that the four compounds comprising were produced in significant amounts during photocatalytic degradation with the two photocatalysts. For the pure TiO\u003csub\u003e2\u003c/sub\u003e, the phenol concentration gradually decreased with the reaction time. It found that the four materials (HQ, BQ, MA and FA) are the main aromatic compounds produced by phenol conversion. The highest concentration of the four materials are detected at 210 min and then decreased gradually, also the MA and FA keep the higher concentration than BQ and HQ, which mightbe caused by the BQ and HQ can turn into MA and FA or the phenol itself will be further converted into maleic acid and fumaric acid, and the residual phenol concentration was 27.17 mg/L after reaction for 420 min. During the phenol photocatalytic degradation over TiO\u003csub\u003e2\u003c/sub\u003e, phenol is gradually degraded in the progress of the reaction, and most of it is directly mineralized into CO\u003csub\u003e2\u003c/sub\u003e and water (Asma Turki 2014).\u003c/p\u003e\n \u003cp\u003eFor the 30% TiO\u003csub\u003e2\u003c/sub\u003e/MMT catalyst, with the extension of the photocatalytic reaction time, the phenol concentration in the residual solution decreased significantly. After 420 min reaction, the residual phenol concentration was 9.36 mg/L. Total benzoquinone (HQ), hydroquinone (BQ), maleic acid and fumaric acid (FA\u0026thinsp;+\u0026thinsp;MA) produced by the photocatalytic degradation system of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT. Compared with the pure TiO\u003csub\u003e2\u003c/sub\u003e system, 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT had more phenol photo-degradation efficiency, and the total amount of intermediate products detected is larger than that in the TiO\u003csub\u003e2\u003c/sub\u003e system. The larger amount of HQ\u0026thinsp;+\u0026thinsp;BQ is due to the higher selectivity of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT in the phenol conversion. The loading of montmorillonite makes๒OH produced by TiO\u003csub\u003e2\u003c/sub\u003e easier to attack the para position of phenol. Hydroquinone is produced and further converted into p-benzoquinone. The amount of butadionic acid (FA\u0026thinsp;+\u0026thinsp;MA) detected in the reaction system of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT for phenol degradation was higher than that of pure TiO\u003csub\u003e2\u003c/sub\u003e. Considering the production of HQ\u0026thinsp;+\u0026thinsp;BQ and FA\u0026thinsp;+\u0026thinsp;MA amount produced in this system, their concentration increased first and then decreased. It is speculated that the reaction course of the montmorillonite loading system may be the rapid phenol mineralization to produce CO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO. The amount of acid produced was small, or is rapidly converted to CO\u003csub\u003e2\u003c/sub\u003e under these catalytic conditions (Xiaobo Wang 2014).\u003c/p\u003e\n \u003cp\u003eThe conversion of phenol calculated by liquid chromatography data was 45.7% (TiO\u003csub\u003e2\u003c/sub\u003e) and 81.9% (30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT), respectively. It was found that the sum of the carbon content of the intermediate substances was much lower than the degradation rate caused by phenol. It is possible that a large amount of carbon was converted into carbon dioxide, leaving the reaction system. In addition, it can be seen from Fig. 10 that almost all the intermediate products of phenol degradation are converted into small molecular substances. With reference to high-performance liquid reaction data and a large amount of literature, it is concluded that under this experimental condition, the reaction mechanism of phenol degradation may be like this:\u003c/p\u003e\n \u003cp\u003eThe good photocatalytic activity of the 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites can be ascribed to the following reasons. The photocatalytic mechanism of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites is showed in Fig.\u0026nbsp;10. TiO\u003csub\u003e2\u003c/sub\u003e in the interlayer of MMT could increase the surface area of TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites,and adding the adsorption efficiency of phenol༌thus promoting the photodegradation efficiency of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT. Secondly, TiO\u003csub\u003e2\u003c/sub\u003e loaded on the surface of MMT and improved its disperse, also enlarged the amount of exposed activates for reactions. When the composite photocatalyst is irradiated by sunlight, the electrons (e\u003csup\u003e\u0026minus;\u003c/sup\u003e) in the valence band (VB) of TiO\u003csub\u003e2\u003c/sub\u003e will be excited by energy and transfer to the conduction band (CB) to generate photogenerated electrons, which will generate photogenerated holes (hv\u003csup\u003e+\u003c/sup\u003e), Photogenerated holes and electrons will combine with water and dissolved oxygen in water to form superoxide radical (\u0026middot; O\u003csub\u003e2\u003c/sub\u003e \u003csup\u003e\u0026minus;\u003c/sup\u003e) and hydroxyl radical (\u0026middot; OH). The two radicals can oxidize phenol to HQ\u0026thinsp;+\u0026thinsp;HQ, and then convert into FA\u0026thinsp;+\u0026thinsp;MA, and finally mineralize into small molecules of H\u003csub\u003e2\u003c/sub\u003eO and CO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003e1)TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites were prepared by sol\u0026ndash;gel method. The experiment results indicate 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT (600℃,4h) has relatively higher photocatalytic activities than other catalysts. A certain amount of TiO\u003csub\u003e2\u003c/sub\u003e (TiO\u003csub\u003e2\u003c/sub\u003e/MMT\u0026thinsp;=\u0026thinsp;30%) is highly dispersed on MMT surface, and also TiO\u003csub\u003e2\u003c/sub\u003e can cause the layer silicate of MMT to behave as barriers layer of preventing TiO\u003csub\u003e2\u003c/sub\u003e powders from agglomeration and reduce its particle size from 22.51 to 7.68 nm. Besides, the best photoactivity of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composites can be due to its smaller particle size, its layer structure and the red shift of the onset absorption edge in the UV\u0026ndash;Visible DRS.\u003c/p\u003e \u003cp\u003e2)The initial concentration of phenol was 10 mg/L, the initial pH of the solution was 6, the amount of catalyst used was 2 g/L, and the ultraviolet irradiation time was 240min. Under the condition of, the degradation rate of phenol was 89.8%. For phenol with an initial concentration of 50 mg/L, the phenol conversion detected by liquid chromatography reached 81.9% at 420 min. The phenol degradation rate was much higher than that of pure TiO\u003csub\u003e2\u003c/sub\u003e (45.7%) under the same conditions, indicating that the loading of montmorillonite significantly enhanced the photocatalytic degradation of phenol by TiO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present study was supported by the Joint Project of Basic Agricultural Research Fund of Yunnan Province (2018FG001-051).\u003c/p\u003e\n\u003cp\u003eThe manuscript does not applicable for ethical approval and consent to participate. This study was supported in part by grants from the Joint Project of Basic Agricultural Research Fund of Yunnan Province (2018FG001-051). And all the authors consent to publish. The authors declare that they have no competing interests. All data generated or analyzed during this study are included in this published article.\u003c/p\u003e\n\u003cp\u003eThe authors\u0026rsquo; contributions are followed as:\u003c/p\u003e\n\u003cp\u003eHuijuan Li contributed to the conception of the study and wrote the manuscript;\u003c/p\u003e\n\u003cp\u003eYeting Yao contributed significantly to analysis and manuscript preparation\u003c/p\u003e\n\u003cp\u003eXiaoyan Yang contributed to make the graphs in the manuscript.\u003c/p\u003e\n\u003cp\u003eXusheng Zhou performed the experiment;\u003c/p\u003e\n\u003cp\u003eRan Lei performed the data analyses;\u003c/p\u003e\n\u003cp\u003eShufang He helped perform the analysis with constructive discussions.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e\u003cspan\u003eGundogdu A, Duran C, Basri Senturk H, Soylak M, Ozdes D, Serencam H, Imamoglu M (2012) Adsorption of Phenol from Aqueous Solution on a Low-Cost Activated Carbon Produced from Tea Industry Waste: Equilibrium, Kinetic, and Thermodynamic Study [J]. Chem Eng Data 57:2733\u0026ndash;2743. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/je300597\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eAydin Hassani A, Khataee S, Karaca (2015) Photocatalytic degradation of ciprofloxacin by synthesized TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles on montmorillonite: Effect of operation parameters and artificial neural network modeling [J]. J Mol Catal A: Chem 409:149\u0026ndash;161. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.molcata.2015.08.020\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eAsma Turki C, Guillard, Fr\u0026eacute;d\u0026eacute;ric Dappozze, Zouhaier Ksibi ,GillesBerhault, Hafedh Kochkar, Phenol photocatalytic degradation over anisotropic TiO \u003csub\u003e2\u003c/sub\u003e nanomaterials: Kinetic study\u0026nbsp;\u003c/span\u003e\u003cspan\u003eadsorption isotherms and formal mechanisms [J] (2015) Appl Catal B 163:404\u0026ndash;413. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.apcatb.2014.08.010\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eBoualem Damardji HK, Duclaux L, David B (2009) Preparation of TiO\u003csub\u003e2\u003c/sub\u003e-pillared montmorillonite as photocatalyst Part I. Microwave calcination, characterisation, and adsorption of a textile azo dye [J]. Appl Clay Sci 44:201\u0026ndash;205. . 10.1016/j.clay.2008.12.010\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eChihiro Ooka H, Yoshida M, Horio K, Suzuki T, Hattori (2003) Adsorptive and photocatalytic performance of TiO\u003csub\u003e2\u003c/sub\u003e pillared montmorillonite in degradation of endocrine disruptors having different hydrophobicity [J]. Appl Catal B 41:313\u0026ndash;321. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S0926-3373(02)00169-8\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eLi C, Zhu N, Yang S, He X, Zheng S, Sun Z, Dionysios D, Dionysiou, A review of clay based photocatalysts: Role of phyllosilicate mineral in\u0026nbsp;\u003c/span\u003e\u003cspan\u003einterfacial assembly, microstructure control and performance regulation [J], Chemosphere, 2021 \u003cspan\u003e273., 129723, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.chemosphere.2021.129723\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eChen D, Zhu Q, Zhou F, Deng X, Li F, Synthesis and photocatalytic performances of the TiO\u003csub\u003e2\u003c/sub\u003e pillared montmorillonite [J], Journal of Hazardous Materials,2012, 235\u0026ndash;236, 186\u0026ndash;193, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.jhazmat.2012.07.038\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eHassan Ouachtak AE, Guerdaoui RH, Akhouairi S, Haouti RE, Hafid N, Addi AA, \u0026Scaron;ljukic\u0026acute; B, Diogo MF, Santos (2021) Mohamed Labd Taha, Highly efficient and fast batch adsorption of orange G dye from polluted water using superb organo-montmorillonite: Experimental study and molecular dynamics investigation. J Mol Liq 335:116560. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.matchemphys.2020.124125\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eHongjuan S, Peng T, Liu B, Xian H (2015) Effects of montmorillonite on phase transition and size of TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles in TiO\u003csub\u003e2\u003c/sub\u003e/montmorillonite nanocomposites [J]. Appl Clay Sci 114:440\u0026ndash;446,. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.clay.2015.06.026\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eHongjuan S, Peng T, Liu B (2015) Haiyang Xian,Effects of montmorillonite on phase transition and size of TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles in TiO\u003csub\u003e2\u003c/sub\u003e/montmorillonite nanocomposites [J]. Appl Clay Sci 114:440\u0026ndash;446. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.clay.2015.06.026\u003c/span\u003e\u003c/span\u003e 0169\u0026ndash;1317\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eMogyoro\u0026acute;si K, D\u0026eacute;k\u0026aacute;ny I, Fendler JH, Preparation and Characterization of Clay Mineral Intercalated Titanium Dioxide Nanoparticles[J], Langmuir 2003, 19, 2938\u0026ndash;2946, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/la025969a\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eChen K, Li J, Wang W, Zhang Y, Wang X, Su H (2011) The preparation of vanadium-doped TiO\u003csub\u003e2\u003c/sub\u003e\u0026ndash;montmorillonite nanocomposites and the photodegradation of sulforhodamine B under visible light irradiation [J]. Appl Surf Sci 257:7276\u0026ndash;7285. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.apsusc.2011.03.104\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eLingeswarran Muniandy F, Adam AR, Mohamed E-P, Ng (2014) The synthesis and characterization of high purity mixed microporous/ mesoporous activated carbon from rice husk using chemical activation with NaOH and KOH [J]. Microporous Mesoporous Mater 197:316\u0026ndash;323. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.micromeso.2014.06.020\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eLila Djouadi H, Khalaf HB, Boutoumi H, Kezzime A, Arturo Santaballa J, Canle M (2018) Degradation of aqueous ketoprofen by heterogeneous photocatalysis using Bi\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e3\u003c/sub\u003e/TiO\u003csub\u003e2\u003c/sub\u003e\u0026ndash;Montmorillonite nanocomposites under simulated solar irradiation [J]. Appl Clay Sci 166:27\u0026ndash;37. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.clay.2018.09.008\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eYuan L, Huang D, Guo W, Yang Q, Yu J, TiO2/montmorillonite nanocomposite for removal of organic pollutant [J], Appl Clay Sci, 2011, 53, 272\u0026ndash;278. doi:\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.clay.2011.03.013\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003ePing Zhang Z, Mo L, Han X, Zhu B, Wang C, Zhang, Preparation and Photocatalytic Performance of Magnetic TiO\u003csub\u003e2\u003c/sub\u003e/Montmorillonite/Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e Nanocomposites [J], Ind Eng Chem Res 2014, 53, 8057\u0026ndash;8061, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp: //dx.doi.org/10.1021/ie5001696\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003ePaulina G\u0026oacute;rska A, Zaleska J, Hupka (2009) Photodegradation of phenol by UV/TiO\u003csub\u003e2\u003c/sub\u003e and Vis/N, C-TiO\u003csub\u003e2\u003c/sub\u003e processes: Comparative mechanistic and kinetic studies [J]. Sep Purif Technol 68:90\u0026ndash;96. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.seppur.2009.04.012\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eRuikun Wang Q, Ma Z, Zhao X, Ye Q, Jin, Zhenghui Zhao,Ji Liu, Adsorption of Surfactants on Coal Surfaces in the Coking Wastewater Environment: Kinetics and Effects on the Slurrying Properties of Coking Wastewater\u0026ndash;Coal Slurry [J], Ind Eng Chem Res 2019, 58, 28, 12825\u0026ndash;12834, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acs.iecr.9b01829\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eDjellabi R, Ghorab MF, Cerrato G, Morandi S, Gatto S, Oldani V, Di Michele A, Bianchi CL (2014) Photoactive TiO\u003csub\u003e2\u003c/sub\u003e\u0026ndash;montmorillonite composite for degradation of organic dyes in water [J]. J Photochem Photobiol A 295:57\u0026ndash;63. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jphotochem.2014.08.017\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eParayil SK, Kibombo HS, Wu C-M, Peng R, Jonas Baltrusaitis b, Ranjit T. Koodali. Enhanced photocatalytic water splitting activity of carbon-modified TiO\u003csub\u003e2\u003c/sub\u003e composite materials synthesized by a green synthetic approach [J]. Int J Hydrogen Energy, 2012, 37, 8257\u0026ndash;8267. https://doi.org/10.1016 /j.ijhydene.2012.02.067\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eShivatharsiny Rasalingama HS, Kibombo C-M, Wu R, Peng J, Baltrusaitis, Ranjit T, Koodali. Competitive role of structural properties of titania\u0026ndash;silica mixed oxides and a mechanistic study of the photocatalytic degradation of phenol [J]. Appl Catal B, 2014, 148\u0026ndash;149, 394\u0026ndash;405, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.apcatb.2013.11.025\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eMakrigianni V, Giannakas A, Daikopoulos C, Deligiannakis Y, I. Konstantinou, Prepara\u003c/span\u003e\u003cspan\u003etion, characterization and photocatalytic performance of pyrolytic-tire-char/TiO\u003csub\u003e2\u003c/sub\u003e composites, toward phenol oxidation in aqueous solutions, Applied Catalysis B: Environmental, 2015, 174, 244\u0026ndash;252, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.apcatb.2015.03.007\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eWang X, Huang S, Zhu L, Tian X, Li S, Tang H, Correlation between the adsorption ability and reduction degree of graphene oxide and tuning of\u0026nbsp;\u003c/span\u003e\u003cspan\u003eadsorption of phenolic compounds [J] (2014) Carbon 69:101\u0026ndash;112. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.1016/j.carbon.2013.11.070\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eLiu YX, Zhang X, Guo L, Wu F (2008) N. S. Deng,Photodegradation of Bisphenol A in the Montmorillonite KSF Suspended Solutions [J],Ind. Eng Chem Res 47:7141\u0026ndash;7146. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/ie800169c\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 is not available with this version.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"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":"Montmorillonite, Titanium dioxide, Sol-gel method, Phenol degradation","lastPublishedDoi":"10.21203/rs.3.rs-848926/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-848926/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eComposites of Titanium (IV) oxide combined with montmorillonite (MMT) with various TiO\u003csub\u003e2\u003c/sub\u003e/MMT were prepared for photocatalysis application. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance UV–visible spectroscopy. The main influential factors such as the TiO\u003csub\u003e2\u003c/sub\u003e/MMT dose, calcined temperature and pH value of the solution were studied. The main intermediates of phenol degradation were determined by High Performance Liquid Chromatography\u0026nbsp;(HPLC). The results showed that the average size of TiO\u003csub\u003e2\u003c/sub\u003e nanoparticles was decreased from 22.51 nm to 10.66 nm through the immobilization on MMT. The components in the interlayer domain were replaced by titanium pillars, and the pillaring reaction proceeded in the interlayer domain, and the basic skeleton of MMT was unchanged, and also TiO\u003csub\u003e2 \u003c/sub\u003ewas dispersed on the surface of the MMT. When the initial concentration of phenol is 10 mg/L, the phenol solution pH is 6 and the UV light irradiation time is 240 min, the phenol degradation rate of 30%TiO\u003csub\u003e2\u003c/sub\u003e/MMT composite is 89.8%, which is better than MMT (11.5%) and pure TiO\u003csub\u003e2\u003c/sub\u003e (58.8%). It shows that TiO\u003csub\u003e2 \u003c/sub\u003eloaded on MMT improves its photocatalytic activity. The phenol reaction process detected by HPLC showed that it had undergone through hydroquinone and benzoquinone, and finally converted into maleic acid and carbon dioxide and small molecules. The possible photocatalysis mechanism is presented.\u003c/p\u003e","manuscriptTitle":"Degradation of Phenol by Photocatalysis Using TiO2/Montmorillonite Composites Under UV Light","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2021-09-27 15:21:20","doi":"10.21203/rs.3.rs-848926/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2022-01-18T14:04:59+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2021-09-22T07:24:50+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2021-09-15T19:38:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2021-08-25T12:15:36+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":"4e063989-44f9-4bff-be35-bed23e124977","owner":[],"postedDate":"September 27th, 2021","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":7469270,"name":"Toxicology"}],"tags":[],"updatedAt":"2022-05-01T07:56:54+00:00","versionOfRecord":[],"versionCreatedAt":"2021-09-27 15:21:20","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-848926","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-848926","identity":"rs-848926","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}