{"paper_id":"4aba79d2-a6a2-41f0-8e49-53f93e9689ab","body_text":"Study on the dissociation of cryolite in SPL | 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 Study on the dissociation of cryolite in SPL Xiping Chen, Fangheng Fang Tang, Hao Liu, Hongwei Xuan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4772482/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 06 Mar, 2025 Read the published version in Korean Journal of Chemical Engineering → Version 1 posted 4 You are reading this latest preprint version Abstract The spent pot lining of aluminum electrolysis (SPL) is a typical harmful solid waste discharged from the production process of primary aluminum. It contains about 30% of fluoride and 0.2% of cyanide, which is a valuable fluorine-containing resource. With SPL as raw material, sodium carbonate was used as a reagent, and dissociation of cryolite was investigated by baking process. Gibbs free energy of cryolite dissociation was calculated and reaction mechanism of cryolite was discussed. At the same time, the effects of reagent addition ratio, baking temperature and reaction time on the dissociation of cryolite in SPL were discussed. The results show that under the conditions of a reagent addition ratio of 30 ~ 35wt%, baking temperature of 800 ~ 850 ℃ and reaction time of 3 ~ 3.5 h, the phase of cryolite and mullite in the SPL disappears, cryolite is transformed into sodium fluoride and sodium metaaluminate compounds, and mullite is transformed into nepheline or feldspar. The concentration of fluoride ion in clinker leaching solution increased to 8.84 g/L, almost two times of primary concentration 4.56 g/L in SPL, and the effect of dissociation was obvious, which will be beneficial to the subsequent recovery of fluorides. Cryolite Baking Dissociation Sodium fluoride Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Aluminum and its alloys, being one of the most extensively utilized metals worldwide, find wide-ranging applications in aerospace, machinery manufacturing, automotive, medical, and various other industries. 1–3 Currently, the primary method employed for aluminum production is the Hall-Heroult molten salt electrolysis technique. 4–7 SPL constitutes the primary solid waste generated during the overhaul of aluminum electrolytic cells, encompassing waste cathode carbon blocks (1-cut) and waste refractory materials (2-cut). 8 Approximately 25 kg of SPL is generated for every ton of aluminum produced, resulting in a global annual output of around 2 million tons. SPL contains significant amounts of fluoride and cyanide, with fluoride being not only highly toxic but also exhibiting strong corrosive properties, posing serious threats to both the ecological environment and human health. 9–11 In June 2016, the Chinese government included SPL in the 'National Hazardous Waste List' with waste code 321-023-48, categorizing it as hazardous due to its leaching toxicity (hazard characteristic 'T'). Similarly, the United States Environmental Protection Agency (USEPA) and the Canadian government also classify SPL as hazardous waste. The main fluorides present in the SPL are sodium fluoride and cryolite, with sodium fluoride being amenable to recycling through water immersion, 12 while separating cryolite from the SPL poses a significant challenge. The scarcity of fluorine resources in China poses a significant challenge. The recovery of fluorides from the SPL holds immense potential for both SPL recycling and conservation of primary fluorine resources. 13 Therefore, numerous scholars have conducted extensive research on the treatment of cryolite in SPL, primarily focusing on the fire and wet methods. Wang et al. from Zhengzhou University employed dolomite as a reactant to effectively reduce soluble fluoride content in SPL distillate. The resulting product predominantly comprised MgO and CaF 2 , which can serve as valuable raw materials and alternative fuels for magnesium smelting using the Pijiang process. 14 Based on the research presented in this paper, Xuan et al. from Zhengzhou University successfully synthesized NaMgF 3 and MgF 2 by employing soluble fluoride as the fluorine source in the leaching solution of major repair residue, thereby achieving efficient utilization of valuable fluorine resources. 15 Zhao et al. investigated the utilization of SPL in cement production by crushing and blending it with a specific proportion of fly ash and limestone, followed by its introduction into the rotary kiln for calcination. 16 Cryolite and other fluorides react with alumina to generate calcium fluoride, aluminum fluoride, and other insoluble byproducts, which subsequently form solid waste residues. Wang et al. investigated the vacuum thermal reduction lime curing method for the harmless treatment of waste refractory materials in aluminum electrolytic cells. 17 In the reduction process, calcium oxide reacts with sodium fluoride and cryolite to yield calcium fluoride and sodium oxide. The high temperature treatment of SPL transforms cryolite into non-toxic and insoluble calcium fluoride, achieving harmless disposal of SPL; however, it does not exploit the potential utilization of fluoride in the waste. Tan et al employed wet grinding, leaching, and oxidation techniques to treat SPL. In this process, a combination of oxidizing agents such as calcium hypochlorite and calcium carbide slag were mixed with SPL, while water was added as a grinding aid. 18 The fluorine ions underwent a reaction, resulting in the formation of CaF 2 within the residue, while the SPL was converted into generic industrial solid waste. Nie et al. investigated the impact of an acidic iron-containing solution on the efficiency of fluoride removal from aluminum electrolytic SPL. 19 T.K. Pong et al. employed a low-temperature chemical leaching process to recover CaF 2 and AlF 3 products from overhaul slag, utilizing aqueous fluosilicic acid (H 2 SiF 6 ) for the dissolution of micro-dissolved cryolite and calcium fluoride. 20 The aforementioned acid leaching method for treating SPL involves immersing sodium fluoride, cryolite, and other fluorides into an acidic solution to mitigate the detrimental effects of fluoride in SPL. However, the subsequent treatment of the acid leaching solution necessitates substantial energy and cost consumption, posing challenges for its large-scale implementation. Zhang et al. investigated the efficacy of bleaching powder as a cyanide removal agent and calcium hydroxide as a fluoride removal agent while examining the impact of various reaction conditions on the effectiveness of cyanide and fluoride elimination. 21 Du et al. employed a two-stage oxidation method to effectively eliminate cyanide and fluoride from the SPL, resulting in the production of harmless tailings that meet standard requirements. 22 The methods mentioned above also facilitate the conversion of cryolite into calcium fluoride within the tail slag, posing challenges in harnessing its fluorine component. In this study, a new process is proposed that uses sodium carbonate as reaction aid for high-temperature roasting, which can successfully be achieved by the decomposition of SPL. The cryolite underwent a transformation process, resulting in the formation of soluble sodium fluoride and sodium metaaluminate, while mullite was converted into sodium aluminium silicate. Simultaneously, the effects of reaction time, roasting temperature, and catalyst ratio on the process were studied. The conversion mechanism was also systematically discussed. 2. Experimental materials and methods 2.1. Raw material In order to ensure optimal mixing and reaction efficiency in the experiment, the experimental SPL was finely ground to a particle size of less than 120 mesh and stored for subsequent use. The sodium carbonate utilized in the experiment was sourced as a pure analytical reagent from Sinopharm Group. Deionized water was employed as the experimental solvent. 2.2. Characterization methods The samples were analyzed using XRF (ARL PERFORM ’X) for elemental analysis, Empyrean sharp XRD (XRD-6100, scanning voltage 40 kV, scanning current 30 mA) for phase composition determination, and SEM-EDS (FEI Nova Nao SEM 450, EDAX Octane Supper, Scanning voltage 15 kV) for morphology analysis. The concentration of fluoride ions in the leaching solution was measured by ion chromatography (ICS-6000, Shenghan Qingdao). The roasting loss rate is determined by applying Eq. 1: Y=(M-M 0 )/M·100% ( 1 ) Where Y - roasting loss rate, expressed as a percentage; M - total mass of the mixture, measured in grams; M 0 - clinker quantity after roasting, measured in grams. Leaching loss is determined by utilizing Eq. 2: Y 1 = (m 0 -m 1 )/m 0 ·100% ( 2 ) Where Y 1 represents the rate of water immersion loss, expressed as a percentage, m 0 represents the initial quantity of SPL clinker before water immersion, measured in grams, and m 1 represents the final quantity of SPL clinker after water immersion, also measured in grams. 2.3. Experimental procedure The raw material used was 30 g of SPL each time. Sodium carbonate was added in different ingredient ratios, and the mixture was roasted at various temperatures and durations to generate a burning loss rate curve. The resulting clinker was immersed in deionized water for 4 hours on a shaker, followed by a 2-hour settling period to obtain the water-leaching solution and residue. Subsequently, the water immersion loss rate was calculated and fluorine ion content in the solution were measured. The experimental procedure is illustrated in Fig. 1 . 2.4. Reaction principle The composition of the SPL is intricate, comprising mullite, sodium fluoride, calcium fluoride, cryolite and carbon, among others. During the heating process, carbides, nitrides and cyanide undergo oxidative decomposition reactions to produce alumina and sodium oxide. The added reaction additives react with mullite and cryolite as follows, the reaction mechanism of cryolite and reaction additive is shown in Fig. 2 . Al 2 O 3 ·SiO 2 + Na 2 CO 3 = NaAlSiO 4 + NaAlO 2 + CO 2 (g) ( 3 ) Na 3 AlF 6 + 2Na 2 CO 3 = NaAlO 2 + 6NaF + 2CO 2 (g) ( 4 ) The Gibbs free energies of reactions ( 3 ) and ( 4 ) are computed and depicted in Fig. 3 . It is evident from the graphical representation that for temperatures exceeding 500℃, the ΔG values of reactions ( 3 ) and ( 4 ) exhibit negativity, indicating spontaneous progression of these reactions. When the temperature is greater than 500℃, the above main reactions can occur. Moreover, an increase in temperature facilitates reaction kinetics. . From the dynamic analysis,, the reaction between SPL and sodium carbonate, a solid-solid reaction system of these solid powders, conformed to the Jander model as shown in Fig. 4 , with the equations as follows: Thickness of the product layer: \\(\\:\\text{y}={\\text{r}}_{0}\\left[1-{\\left(1-\\text{x}\\right)}^{\\frac{1}{3}}\\right]\\) ( 5 ) Parabolic rate equation: \\(\\:{\\text{D}}_{1}\\left(\\text{y}\\right)={\\text{y}}^{2}={\\text{k}}^{{\\prime\\:}}\\text{t}\\left({\\text{k}}^{{\\prime\\:}}=\\frac{2\\text{D}\\varDelta\\:{\\text{C}}_{\\text{A}}}{{\\rho\\:}}\\right)\\) ( 6 ) Conversion rate equation: \\(\\:{\\text{D}}_{2}\\left(\\text{x}\\right)={\\left[1-{\\left(1-\\text{x}\\right)}^{\\frac{1}{3}}\\right]}^{2}=\\text{k}\\text{t}\\left(\\text{k}=\\frac{{\\text{k}}^{{\\prime\\:}}}{{{\\text{r}}_{0}}^{2}}\\right)\\) ( 7 ) Where y is the thickness of product layer AB; r 0 is the initial radius of reactant A's particles; x is the conversion rate based on reactant A; D is the diffusion coefficient of reactant A in the product layer AB; ∆C A is the concentration difference of reactant A between the two ends of product layer AB; ρ is the molar density of reactant A; k is the Jander constant. 2.5. Physical and chemical properties of SPL The chemical composition of SPL was analyzed using a pressing tablet method with an XRF fluorescence spectrometer, as presented in Table 1 . Elements such as oxygen (O), aluminum (Al), silicon (Si), fluorine (F), sodium (Na) and carbon (C) are dense present in SPL, while calcium (Ca), iron (Fe), potassium (K) and sulfur (S) are present in small concentrations (Table 1 ). Table 1 Chemical composition of SPL (mass fraction wt%). Components F O Al Na C Si Ca Fe K S Others Content 10.16 35.19 20.73 5.90 6.12 15.04 2.05 1.83 1.52 0.60 0.86 In order to comprehend the physical and chemical properties of SPL, XRD, and SEM-EDS analyses were performed on the raw materials of SPL, with the results presented in Fig. 5 . The XRD pattern in Fig. 5 a reveals that mullite, NaF, cryolite, calcium fluoride, and other components constitute the major constituents of SPL. As depicted in Fig. 5 b by SEM-EDS analysis, SPL exhibits an irregular massive structure with cryolite predominant at point 1 while sodium fluoride, cryolite, and alumina dominate at point 2. Mullite and potassium sodium cryolite are identified as the primary compounds at point 3. The element distribution cloud map displayed in Fig. 5 c demonstrates dense element distribution for Al, C, F, Na O, and Si, whereas K, Ca, and other elements exhibit sparse distribution. 3. Results and discussions According to the foregoing theoretical analysis, the chemical transformation of cryolite and mullite is expected to occur when sodium carbonate is mixed with SPL and subjected to high temperature roasting under specific conditions. This study investigated the influence of additive quantity, reaction time, and reaction temperature on the dissociation of SPL. 3.1. Influence of reaction auxiliary additive quantity on the dissociation of SPL The influence of the additional amount of reaction additives on the dissociation of SPL was investigated under reaction conditions of 800℃ for 2 hours. The addition ratio of reaction additives ranged from 0–40%, with an increment of 5%. The results are presented in Fig. 6 . As depicted in Fig. 6 a, the roasting loss rate reaches its maximum value (21.2%) when the amount of reaction additives is set at 30%, indicating a complete reaction between the additives and SPL. Additionally, as shown in Fig. 6 b, when adding a quantity of reaction additives equal to 30%, the concentration of fluoride ions increases from an initial value (4.56g/L) to a peak value (8.93g/L). This increase can be attributed to chemical transformations within crystalline structures leading to sodium fluoride formation and the subsequent influx of more fluoride ions into the solution. Furthermore, Fig. 6 c reveals that with increasing amounts of reaction additives, characteristic peaks corresponding to mullite and cryolite disappear while those associated with sodium metaaluminate, sodium fluoride, and nepheline become significantly enhanced; this observation suggests dissociation reactions occurring between cryolite and mullite resulting in production of sodium fluoride, nepheline, and sodium metaaluminate compounds. After conducting a comprehensive analysis, it is recommended to select an appropriate addition amount of reaction aids at approximately 30%. 3.2 Influence of roasting temperature on the dissociation of SPL The influence of reaction temperature on the dissolution of SPL was investigated under the conditions of a 30% additive amount and a 2-hour reaction time. The reaction temperature ranged from 700 to 850℃ with an increment of 50℃, and the results are presented in Fig. 7 . According to the analysis depicted in Fig. 7 a, when the temperature reaches or exceeds 800℃, the roasting loss rate stabilizes at approximately 21%, indicating that the reaction efficiency has reached a relatively high level. Further temperature increases have minimal impact on efficiency. Simultaneously, as shown in Fig. 7 b, at a temperature of 800℃, the fluoride ion concentration reaches about 8.84g/L and remains stable at a high level along with the water immersion loss rate. Additionally, as observed from Fig. 7 c, characteristic peaks corresponding to mullite and cryolite disappear with increasing temperatures, while those associated with sodium metaaluminate, sodium fluoride, and nepheline become more prominent. Therefore, it obviously suggests that cryolite and mullite undergo dissociation to produce sodium fluoride, nepheline, and sodium metaaluminate. Based on comprehensive analysis, an appropriate reaction temperature range would be between 800 ~ 850℃. 3.3 Influence of roasting time on the dissociation of SPL The influence of reaction time on the dissolution of SPL was investigated under the conditions of 30% additive and a reaction temperature of 800℃. The reaction time ranged from 1 to 4 hours, with increments of 0.5 hours, and the results are presented in Fig. 8 . As depicted in Fig. 8 a, when the roasting time reaches 3 hours, the roasting loss rate stabilizes at approximately 21%, indicating a relatively high level of reaction efficiency. Simultaneously, as shown in Fig. 8 b, for roasting times exceeding 3 hours, the fluoride ion concentration reaches a steady range between 8.84 g/L and 8.93 g/L while maintaining a high level along with water immersion loss rate stability. Furthermore, Fig. 8 c collectively reveals that mullite and cryolite characteristic peaks diminish with prolonged reaction time while sodium metaaluminate and sodium fluoride peaks become significantly enhanced alongside nepheline formation; this suggests dissociation of cryolite and mullite into sodium fluoride, nepheline, and sodium metaaluminate occurs during the process. Based on comprehensive analysis, an appropriate roasting time would be within the range of approximately 3 to 3.5 hours. As indicated by the aforementioned research findings, the satisfactory process conditions are as follows: a reaction additive addition ratio of 30 ~ 35%, a roasting temperature ranging from 800 to 850°C, and a roasting time of 3 ~ 3.5 hours. During this process, mullite is transformed into sodium aluminium silicate while cryolite undergoes conversion into soluble sodium fluoride and sodium metaaluminate. Consequently, there is an increase in fluoride ions concentration from 4.56g/L to approximately 8.84g/L in the leaching solution, achieving the desired dissolution and dissociation effect. Sodium fluoride exhibits high solubility in water, enabling its separation from the residual material through immersion for facilitating subsequent fluoride recovery. 3.4 Physical and chemical properties of reaction products Under the experimental conditions of a 30% addition ratio of reaction additive, roasting at a temperature of 800℃ for 3 hours was conducted on the SPL mixture, followed by high-temperature roasting and water leaching experiments. The resulting leaching slag was subsequently dried. XRD and SEM-EDS analyses were performed on the roasted products and water-leaching residue, with the corresponding results presented in Fig. 9 . The XRD patterns of the calcined clinker and water impregnated slag obtained under the optimized experimental conditions are presented in Fig. 9 . The disappearance of cryolite characteristic peaks after roasting indicates a chemical reaction between cryolite and the reaction additives, resulting in soluble sodium metaaluminate and sodium fluoride (Fig. 9 a). The leaching residue was subjected to SEM-EDS analysis, as depicted in Fig. 9 b. The energy spectrum dot scan revealed a significant weakening of the F peak (Fig. 9 b) compared to Fig. 5 b, indicating dissociation of cryolite and subsequent immersion of fluorine ions in water, leading them to leave the matrix. The SEM-EDS results were consistent with those obtained from XRD. 4. Conclusions This study utilized SPL as the raw material and sodium carbonate as the reaction agent. The outcomes of our investigations revealed that high-temperature roasting can induce the dissolution of SPL, transforming mullite into nepheline and cryolite into soluble sodium fluoride and sodium metaaluminate. Thermodynamic calculations demonstrate that chemical reactions between mullite/cryolite and reaction additives can occur at 700 ~ 850℃, better at 800 ~ 850℃ to produce nepheline/sodium fluoride/sodium metaaluminate, respectively. In addition, under conditions of a 30 ~ 35% additive ratio with an 800 ~ 850℃ reaction temperature for 3 ~ 3.5 hours duration yields better dissociation effects on SPL while achieving complete conversion of cryolite/mullite; furthermore, increasing concentration levels of fluoride ions from clinker water immersion solution from 4.56g/L to nearly double at 8.84 g/L. Declarations CRediT authorship contribution statement Fangheng Tang : Experimental research, article writing. Xiping Chen : Experimental scheme approval, data analysis, article improvement. Hao liu : Chemical analysis. Hongwei Xuan : Scheme formulation. 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Shandong Industrial Technology, 2021(5): 9-12, https://doi.org/10.16640/j.cnki.37-1222/t.2021.05.002. Du Tingting et al. Study on the harmless disposal technology of toxic substances in spent potlining. Light Metals, 2020(11): 32-35, https://doi.org/10.13662/j.cnki.qjs.2020.11.009. Cite Share Download PDF Status: Published Journal Publication published 06 Mar, 2025 Read the published version in Korean Journal of Chemical Engineering → Version 1 posted Reviewers agreed at journal 06 Aug, 2024 Reviewers invited by journal 05 Aug, 2024 Editor assigned by journal 23 Jul, 2024 First submitted to journal 20 Jul, 2024 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. 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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-4772482\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Research Article\",\"associatedPublications\":[],\"authors\":[{\"id\":336170232,\"identity\":\"c6b7284c-7352-4fce-ac9e-6d2fc33ebdd0\",\"order_by\":0,\"name\":\"Xiping 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09:49:28\",\"currentVersionCode\":1,\"declarations\":\"\",\"doi\":\"10.21203/rs.3.rs-4772482/v1\",\"doiUrl\":\"https://doi.org/10.21203/rs.3.rs-4772482/v1\",\"draftVersion\":[],\"editorialEvents\":[{\"content\":\"https://doi.org/10.1007/s11814-025-00412-5\",\"type\":\"published\",\"date\":\"2025-03-06T15:57:06+00:00\"}],\"editorialNote\":\"\",\"failedWorkflow\":false,\"files\":[{\"id\":63621703,\"identity\":\"20cead20-5371-4866-9d25-60b51081591a\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 08:56:25\",\"extension\":\"png\",\"order_by\":1,\"title\":\"Figure 1\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":167268,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eFlowchart of the operational procedure\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/a1c9ebb172fc9f302af4604c.png\"},{\"id\":63621712,\"identity\":\"6c20b505-3eff-4c00-9b43-285c00292a3c\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 08:56:26\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":542459,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eSchematic diagram of the reaction mechanism of cryolite and reaction additives\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.2.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/46ead95f624d5f33d53142f5.png\"},{\"id\":63622280,\"identity\":\"5cd85ca9-548e-4fb8-82b6-791a85ab7777\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 09:04:25\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":55690,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eGibbs free energy trend chart of the reaction of SPL and sodium carbonate\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/764bfdc401f8a263936d8c1f.png\"},{\"id\":63621711,\"identity\":\"cf28c771-c89d-4dd1-9b04-b59d3c927128\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 08:56:26\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":282576,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eThe Jander model diagram for spherical particles.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.4.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/27dcc4a7e67ed2750233279f.png\"},{\"id\":63622282,\"identity\":\"f3b0e387-3d35-4324-a330-0737f614c265\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 09:04:25\",\"extension\":\"png\",\"order_by\":5,\"title\":\"Figure 5\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":1228014,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eCharacterization of SPL: (a) XRD, (b) SEM-EDS, (c) Element distribution cloud map\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.5.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/fa2a5e6ee547442596210ca4.png\"},{\"id\":63622281,\"identity\":\"f8939192-0bbd-4ca5-90a3-01f36d1d51e9\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 09:04:25\",\"extension\":\"png\",\"order_by\":6,\"title\":\"Figure 6\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":55865,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eEffect of the quantity of reaction additives on the dissociation of SPL: (a) Loss rate during roasting, (b) Concentration of fluoride ions and loss rate in water immersion solution, (c) XRD pattern of the roasted product.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.6.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/07fbe885d31228f10c280f39.png\"},{\"id\":63621707,\"identity\":\"0d6922f2-440d-4829-981d-0ca8b047bc08\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 08:56:25\",\"extension\":\"png\",\"order_by\":7,\"title\":\"Figure 7\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":52151,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eEffect of the roasting temperature on the dissociation of SPL: (a) Loss rate during roasting; (b) Concentration of fluoride ions and loss rate in water immersion solution; (c) XRD pattern of the roasted product.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.7.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/8d5a5307feee32ffcf03d93f.png\"},{\"id\":63621706,\"identity\":\"ae9d10b1-c031-41be-946f-1140d658962a\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 08:56:25\",\"extension\":\"png\",\"order_by\":8,\"title\":\"Figure 8\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":46980,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eEffect of the roasting time on the dissociation of SPL: (a) Loss rate during roasting; (b) Concentration of fluoride ions and loss rate in water immersion solution; (c) XRD pattern of the roasted product.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.8.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/9938b4b1df02c0064719fb93.png\"},{\"id\":63621710,\"identity\":\"1dc52ac3-f696-4b0b-a0c2-5d9c8a5c23cf\",\"added_by\":\"auto\",\"created_at\":\"2024-08-30 08:56:25\",\"extension\":\"png\",\"order_by\":9,\"title\":\"Figure 9\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":361461,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eCharacterization of reaction products: (a) XRD spectrum of the raw material, roasted clinker and water-leaching residue; (b) SEM-EDS of the water-leaching residue.\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"Fig.9.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/e8661a64554b06ab3c7f8c3b.png\"},{\"id\":78191252,\"identity\":\"f601479b-436f-410a-b8da-b1bb4c883bec\",\"added_by\":\"auto\",\"created_at\":\"2025-03-10 19:54:15\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":3739089,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-4772482/v1/8b3b6972-5aa7-4f80-bdd8-05f1e54670b9.pdf\"}],\"financialInterests\":\"\",\"formattedTitle\":\"Study on the dissociation of cryolite in SPL\",\"fulltext\":[{\"header\":\"1. Introduction\",\"content\":\"\\u003cp\\u003eAluminum and its alloys, being one of the most extensively utilized metals worldwide, find wide-ranging applications in aerospace, machinery manufacturing, automotive, medical, and various other industries.\\u003csup\\u003e1\\u0026ndash;3\\u003c/sup\\u003e Currently, the primary method employed for aluminum production is the Hall-Heroult molten salt electrolysis technique.\\u003csup\\u003e4\\u0026ndash;7\\u003c/sup\\u003e SPL constitutes the primary solid waste generated during the overhaul of aluminum electrolytic cells, encompassing waste cathode carbon blocks (1-cut) and waste refractory materials (2-cut).\\u003csup\\u003e8\\u003c/sup\\u003e Approximately 25 kg of SPL is generated for every ton of aluminum produced, resulting in a global annual output of around 2\\u0026nbsp;million tons. SPL contains significant amounts of fluoride and cyanide, with fluoride being not only highly toxic but also exhibiting strong corrosive properties, posing serious threats to both the ecological environment and human health.\\u003csup\\u003e9\\u0026ndash;11\\u003c/sup\\u003e In June 2016, the Chinese government included SPL in the 'National Hazardous Waste List' with waste code 321-023-48, categorizing it as hazardous due to its leaching toxicity (hazard characteristic 'T'). Similarly, the United States Environmental Protection Agency (USEPA) and the Canadian government also classify SPL as hazardous waste. The main fluorides present in the SPL are sodium fluoride and cryolite, with sodium fluoride being amenable to recycling through water immersion,\\u003csup\\u003e12\\u003c/sup\\u003e while separating cryolite from the SPL poses a significant challenge. The scarcity of fluorine resources in China poses a significant challenge. The recovery of fluorides from the SPL holds immense potential for both SPL recycling and conservation of primary fluorine resources.\\u003csup\\u003e13\\u003c/sup\\u003e\\u003c/p\\u003e \\u003cp\\u003eTherefore, numerous scholars have conducted extensive research on the treatment of cryolite in SPL, primarily focusing on the fire and wet methods. Wang et al. from Zhengzhou University employed dolomite as a reactant to effectively reduce soluble fluoride content in SPL distillate. The resulting product predominantly comprised MgO and CaF\\u003csub\\u003e2\\u003c/sub\\u003e, which can serve as valuable raw materials and alternative fuels for magnesium smelting using the Pijiang process.\\u003csup\\u003e14\\u003c/sup\\u003e Based on the research presented in this paper, Xuan et al. from Zhengzhou University successfully synthesized NaMgF\\u003csub\\u003e3\\u003c/sub\\u003e and MgF\\u003csub\\u003e2\\u003c/sub\\u003e by employing soluble fluoride as the fluorine source in the leaching solution of major repair residue, thereby achieving efficient utilization of valuable fluorine resources.\\u003csup\\u003e15\\u003c/sup\\u003e Zhao et al. investigated the utilization of SPL in cement production by crushing and blending it with a specific proportion of fly ash and limestone, followed by its introduction into the rotary kiln for calcination.\\u003csup\\u003e16\\u003c/sup\\u003e Cryolite and other fluorides react with alumina to generate calcium fluoride, aluminum fluoride, and other insoluble byproducts, which subsequently form solid waste residues. Wang et al. investigated the vacuum thermal reduction lime curing method for the harmless treatment of waste refractory materials in aluminum electrolytic cells.\\u003csup\\u003e17\\u003c/sup\\u003e In the reduction process, calcium oxide reacts with sodium fluoride and cryolite to yield calcium fluoride and sodium oxide. The high temperature treatment of SPL transforms cryolite into non-toxic and insoluble calcium fluoride, achieving harmless disposal of SPL; however, it does not exploit the potential utilization of fluoride in the waste.\\u003c/p\\u003e \\u003cp\\u003eTan et al employed wet grinding, leaching, and oxidation techniques to treat SPL. In this process, a combination of oxidizing agents such as calcium hypochlorite and calcium carbide slag were mixed with SPL, while water was added as a grinding aid.\\u003csup\\u003e18\\u003c/sup\\u003e The fluorine ions underwent a reaction, resulting in the formation of CaF\\u003csub\\u003e2\\u003c/sub\\u003e within the residue, while the SPL was converted into generic industrial solid waste. Nie et al. investigated the impact of an acidic iron-containing solution on the efficiency of fluoride removal from aluminum electrolytic SPL.\\u003csup\\u003e19\\u003c/sup\\u003e T.K. Pong et al. employed a low-temperature chemical leaching process to recover CaF\\u003csub\\u003e2\\u003c/sub\\u003e and AlF\\u003csub\\u003e3\\u003c/sub\\u003e products from overhaul slag, utilizing aqueous fluosilicic acid (H\\u003csub\\u003e2\\u003c/sub\\u003eSiF\\u003csub\\u003e6\\u003c/sub\\u003e) for the dissolution of micro-dissolved cryolite and calcium fluoride.\\u003csup\\u003e20\\u003c/sup\\u003e The aforementioned acid leaching method for treating SPL involves immersing sodium fluoride, cryolite, and other fluorides into an acidic solution to mitigate the detrimental effects of fluoride in SPL. However, the subsequent treatment of the acid leaching solution necessitates substantial energy and cost consumption, posing challenges for its large-scale implementation. Zhang et al. investigated the efficacy of bleaching powder as a cyanide removal agent and calcium hydroxide as a fluoride removal agent while examining the impact of various reaction conditions on the effectiveness of cyanide and fluoride elimination.\\u003csup\\u003e21\\u003c/sup\\u003e Du et al. employed a two-stage oxidation method to effectively eliminate cyanide and fluoride from the SPL, resulting in the production of harmless tailings that meet standard requirements.\\u003csup\\u003e22\\u003c/sup\\u003e The methods mentioned above also facilitate the conversion of cryolite into calcium fluoride within the tail slag, posing challenges in harnessing its fluorine component.\\u003c/p\\u003e \\u003cp\\u003eIn this study, a new process is proposed that uses sodium carbonate as reaction aid for high-temperature roasting, which can successfully be achieved by the decomposition of SPL. The cryolite underwent a transformation process, resulting in the formation of soluble sodium fluoride and sodium metaaluminate, while mullite was converted into sodium aluminium silicate. Simultaneously, the effects of reaction time, roasting temperature, and catalyst ratio on the process were studied. The conversion mechanism was also systematically discussed.\\u003c/p\\u003e\"},{\"header\":\"2. Experimental materials and methods\",\"content\":\"\\u003cdiv id=\\\"Sec3\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e2.1. Raw material\\u003c/h2\\u003e \\u003cp\\u003eIn order to ensure optimal mixing and reaction efficiency in the experiment, the experimental SPL was finely ground to a particle size of less than 120 mesh and stored for subsequent use. The sodium carbonate utilized in the experiment was sourced as a pure analytical reagent from Sinopharm Group. Deionized water was employed as the experimental solvent.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec4\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e2.2. Characterization methods\\u003c/h2\\u003e \\u003cp\\u003eThe samples were analyzed using XRF (ARL PERFORM \\u0026rsquo;X) for elemental analysis, Empyrean sharp XRD (XRD-6100, scanning voltage 40 kV, scanning current 30 mA) for phase composition determination, and SEM-EDS (FEI Nova Nao SEM 450, EDAX Octane Supper, Scanning voltage 15 kV) for morphology analysis. The concentration of fluoride ions in the leaching solution was measured by ion chromatography (ICS-6000, Shenghan Qingdao).\\u003c/p\\u003e \\u003cp\\u003eThe roasting loss rate is determined by applying Eq.\\u0026nbsp;1:\\u003c/p\\u003e \\u003cp\\u003eY=(M-M\\u003csub\\u003e0\\u003c/sub\\u003e)/M\\u0026middot;100% (\\u003cspan citationid=\\\"CR1\\\" class=\\\"CitationRef\\\"\\u003e1\\u003c/span\\u003e)\\u003c/p\\u003e \\u003cp\\u003eWhere Y - roasting loss rate, expressed as a percentage; M - total mass of the mixture, measured in grams; M\\u003csub\\u003e0\\u003c/sub\\u003e - clinker quantity after roasting, measured in grams.\\u003c/p\\u003e \\u003cp\\u003eLeaching loss is determined by utilizing Eq.\\u0026nbsp;2:\\u003c/p\\u003e \\u003cp\\u003eY\\u003csub\\u003e1\\u003c/sub\\u003e= (m\\u003csub\\u003e0\\u003c/sub\\u003e-m\\u003csub\\u003e1\\u003c/sub\\u003e)/m\\u003csub\\u003e0\\u003c/sub\\u003e\\u0026middot;100% (\\u003cspan citationid=\\\"CR2\\\" class=\\\"CitationRef\\\"\\u003e2\\u003c/span\\u003e)\\u003c/p\\u003e \\u003cp\\u003eWhere Y\\u003csub\\u003e1\\u003c/sub\\u003e represents the rate of water immersion loss, expressed as a percentage, m\\u003csub\\u003e0\\u003c/sub\\u003e represents the initial quantity of SPL clinker before water immersion, measured in grams, and m\\u003csub\\u003e1\\u003c/sub\\u003e represents the final quantity of SPL clinker after water immersion, also measured in grams.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec5\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e2.3. Experimental procedure\\u003c/h2\\u003e \\u003cp\\u003eThe raw material used was 30 g of SPL each time. Sodium carbonate was added in different ingredient ratios, and the mixture was roasted at various temperatures and durations to generate a burning loss rate curve. The resulting clinker was immersed in deionized water for 4 hours on a shaker, followed by a 2-hour settling period to obtain the water-leaching solution and residue. Subsequently, the water immersion loss rate was calculated and fluorine ion content in the solution were measured. The experimental procedure is illustrated in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec6\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e2.4. Reaction principle\\u003c/h2\\u003e \\u003cp\\u003eThe composition of the SPL is intricate, comprising mullite, sodium fluoride, calcium fluoride, cryolite and carbon, among others. During the heating process, carbides, nitrides and cyanide undergo oxidative decomposition reactions to produce alumina and sodium oxide. The added reaction additives react with mullite and cryolite as follows, the reaction mechanism of cryolite and reaction additive is shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig2\\\" class=\\\"InternalRef\\\"\\u003e2\\u003c/span\\u003e.\\u003c/p\\u003e \\u003cp\\u003eAl\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e3\\u003c/sub\\u003e\\u0026middot;SiO\\u003csub\\u003e2\\u003c/sub\\u003e\\u0026thinsp;+\\u0026thinsp;Na\\u003csub\\u003e2\\u003c/sub\\u003eCO\\u003csub\\u003e3\\u003c/sub\\u003e\\u0026thinsp;=\\u0026thinsp;NaAlSiO\\u003csub\\u003e4\\u003c/sub\\u003e\\u0026thinsp;+\\u0026thinsp;NaAlO\\u003csub\\u003e2\\u003c/sub\\u003e\\u0026thinsp;+\\u0026thinsp;CO\\u003csub\\u003e2\\u003c/sub\\u003e(g) (\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e)\\u003c/p\\u003e \\u003cp\\u003eNa\\u003csub\\u003e3\\u003c/sub\\u003eAlF\\u003csub\\u003e6\\u003c/sub\\u003e\\u0026thinsp;+\\u0026thinsp;2Na\\u003csub\\u003e2\\u003c/sub\\u003eCO\\u003csub\\u003e3\\u003c/sub\\u003e\\u0026thinsp;=\\u0026thinsp;NaAlO\\u003csub\\u003e2\\u003c/sub\\u003e\\u0026thinsp;+\\u0026thinsp;6NaF\\u0026thinsp;+\\u0026thinsp;2CO\\u003csub\\u003e2\\u003c/sub\\u003e(g) (\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e)\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eThe Gibbs free energies of reactions (\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e) and (\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e) are computed and depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig3\\\" class=\\\"InternalRef\\\"\\u003e3\\u003c/span\\u003e. It is evident from the graphical representation that for temperatures exceeding 500℃, the ΔG values of reactions (\\u003cspan citationid=\\\"CR3\\\" class=\\\"CitationRef\\\"\\u003e3\\u003c/span\\u003e) and (\\u003cspan citationid=\\\"CR4\\\" class=\\\"CitationRef\\\"\\u003e4\\u003c/span\\u003e) exhibit negativity, indicating spontaneous progression of these reactions. When the temperature is greater than 500℃, the above main reactions can occur. Moreover, an increase in temperature facilitates reaction kinetics.\\u003c/p\\u003e \\u003cp\\u003e.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eFrom the dynamic analysis,, the reaction between SPL and sodium carbonate, a solid-solid reaction system of these solid powders, conformed to the Jander model as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig4\\\" class=\\\"InternalRef\\\"\\u003e4\\u003c/span\\u003e, with the equations as follows:\\u003c/p\\u003e \\u003cp\\u003eThickness of the product layer:\\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:\\\\text{y}={\\\\text{r}}_{0}\\\\left[1-{\\\\left(1-\\\\text{x}\\\\right)}^{\\\\frac{1}{3}}\\\\right]\\\\)\\u003c/span\\u003e\\u003c/span\\u003e (\\u003cspan citationid=\\\"CR5\\\" class=\\\"CitationRef\\\"\\u003e5\\u003c/span\\u003e)\\u003c/p\\u003e \\u003cp\\u003eParabolic rate equation:\\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{D}}_{1}\\\\left(\\\\text{y}\\\\right)={\\\\text{y}}^{2}={\\\\text{k}}^{{\\\\prime\\\\:}}\\\\text{t}\\\\left({\\\\text{k}}^{{\\\\prime\\\\:}}=\\\\frac{2\\\\text{D}\\\\varDelta\\\\:{\\\\text{C}}_{\\\\text{A}}}{{\\\\rho\\\\:}}\\\\right)\\\\)\\u003c/span\\u003e\\u003c/span\\u003e (\\u003cspan citationid=\\\"CR6\\\" class=\\\"CitationRef\\\"\\u003e6\\u003c/span\\u003e)\\u003c/p\\u003e \\u003cp\\u003eConversion rate equation:\\u003cspan class=\\\"InlineEquation\\\"\\u003e\\u003cspan class=\\\"mathinline\\\"\\u003e\\\\(\\\\:{\\\\text{D}}_{2}\\\\left(\\\\text{x}\\\\right)={\\\\left[1-{\\\\left(1-\\\\text{x}\\\\right)}^{\\\\frac{1}{3}}\\\\right]}^{2}=\\\\text{k}\\\\text{t}\\\\left(\\\\text{k}=\\\\frac{{\\\\text{k}}^{{\\\\prime\\\\:}}}{{{\\\\text{r}}_{0}}^{2}}\\\\right)\\\\)\\u003c/span\\u003e\\u003c/span\\u003e (\\u003cspan citationid=\\\"CR7\\\" class=\\\"CitationRef\\\"\\u003e7\\u003c/span\\u003e)\\u003c/p\\u003e \\u003cp\\u003eWhere y is the thickness of product layer AB; r\\u003csub\\u003e0\\u003c/sub\\u003e is the initial radius of reactant A's particles; x is the conversion rate based on reactant A; D is the diffusion coefficient of reactant A in the product layer AB; ∆C\\u003csub\\u003eA\\u003c/sub\\u003e is the concentration difference of reactant A between the two ends of product layer AB; ρ is the molar density of reactant A; k is the Jander constant.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec7\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e2.5. Physical and chemical properties of SPL\\u003c/h2\\u003e \\u003cp\\u003eThe chemical composition of SPL was analyzed using a pressing tablet method with an XRF fluorescence spectrometer, as presented in Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e. Elements such as oxygen (O), aluminum (Al), silicon (Si), fluorine (F), sodium (Na) and carbon (C) are dense present in SPL, while calcium (Ca), iron (Fe), potassium (K) and sulfur (S) are present in small concentrations (Table\\u0026nbsp;\\u003cspan refid=\\\"Tab1\\\" class=\\\"InternalRef\\\"\\u003e1\\u003c/span\\u003e).\\u003c/p\\u003e \\u003cp\\u003e \\u003cdiv class=\\\"gridtable\\\"\\u003e\\u003ctable float=\\\"Yes\\\" id=\\\"Tab1\\\" border=\\\"1\\\"\\u003e \\u003ccaption language=\\\"En\\\"\\u003e \\u003cdiv class=\\\"CaptionNumber\\\"\\u003eTable 1\\u003c/div\\u003e \\u003cdiv class=\\\"CaptionContent\\\"\\u003e \\u003cp\\u003eChemical composition of SPL (mass fraction wt%).\\u003c/p\\u003e \\u003c/div\\u003e \\u003c/caption\\u003e \\u003ccolgroup cols=\\\"12\\\"\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c1\\\" colnum=\\\"1\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c2\\\" colnum=\\\"2\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c3\\\" colnum=\\\"3\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c4\\\" colnum=\\\"4\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c5\\\" colnum=\\\"5\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c6\\\" colnum=\\\"6\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c7\\\" colnum=\\\"7\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c8\\\" colnum=\\\"8\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c9\\\" colnum=\\\"9\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c10\\\" colnum=\\\"10\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c11\\\" colnum=\\\"11\\\"\\u003e\\u003c/div\\u003e \\u003cdiv align=\\\"left\\\" class=\\\"colspec\\\" colname=\\\"c12\\\" colnum=\\\"12\\\"\\u003e\\u003c/div\\u003e \\u003cthead\\u003e \\u003ctr\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eComponents\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003eF\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003eO\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003eAl\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003eNa\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003eC\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003eSi\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003eCa\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003eFe\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003eK\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c11\\\"\\u003e \\u003cp\\u003eS\\u003c/p\\u003e \\u003c/th\\u003e \\u003cth align=\\\"left\\\" colname=\\\"c12\\\"\\u003e \\u003cp\\u003eOthers\\u003c/p\\u003e \\u003c/th\\u003e \\u003c/tr\\u003e \\u003c/thead\\u003e \\u003ctbody\\u003e \\u003ctr\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c1\\\"\\u003e \\u003cp\\u003eContent\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c2\\\"\\u003e \\u003cp\\u003e10.16\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c3\\\"\\u003e \\u003cp\\u003e35.19\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c4\\\"\\u003e \\u003cp\\u003e20.73\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c5\\\"\\u003e \\u003cp\\u003e5.90\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c6\\\"\\u003e \\u003cp\\u003e6.12\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c7\\\"\\u003e \\u003cp\\u003e15.04\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c8\\\"\\u003e \\u003cp\\u003e2.05\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c9\\\"\\u003e \\u003cp\\u003e1.83\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c10\\\"\\u003e \\u003cp\\u003e1.52\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c11\\\"\\u003e \\u003cp\\u003e0.60\\u003c/p\\u003e \\u003c/td\\u003e \\u003ctd align=\\\"left\\\" colname=\\\"c12\\\"\\u003e \\u003cp\\u003e0.86\\u003c/p\\u003e \\u003c/td\\u003e \\u003c/tr\\u003e \\u003c/tbody\\u003e \\u003c/colgroup\\u003e \\u003c/table\\u003e\\u003c/div\\u003e \\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eIn order to comprehend the physical and chemical properties of SPL, XRD, and SEM-EDS analyses were performed on the raw materials of SPL, with the results presented in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003e. The XRD pattern in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ea reveals that mullite, NaF, cryolite, calcium fluoride, and other components constitute the major constituents of SPL. As depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003eb by SEM-EDS analysis, SPL exhibits an irregular massive structure with cryolite predominant at point 1 while sodium fluoride, cryolite, and alumina dominate at point 2. Mullite and potassium sodium cryolite are identified as the primary compounds at point 3. The element distribution cloud map displayed in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003ec demonstrates dense element distribution for Al, C, F, Na O, and Si, whereas K, Ca, and other elements exhibit sparse distribution.\\u003c/p\\u003e \\u003c/div\\u003e\"},{\"header\":\"3. Results and discussions\",\"content\":\"\\u003cp\\u003eAccording to the foregoing theoretical analysis, the chemical transformation of cryolite and mullite is expected to occur when sodium carbonate is mixed with SPL and subjected to high temperature roasting under specific conditions. This study investigated the influence of additive quantity, reaction time, and reaction temperature on the dissociation of SPL.\\u003c/p\\u003e \\u003cdiv id=\\\"Sec9\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e3.1. Influence of reaction auxiliary additive quantity on the dissociation of SPL\\u003c/h2\\u003e \\u003cp\\u003eThe influence of the additional amount of reaction additives on the dissociation of SPL was investigated under reaction conditions of 800℃ for 2 hours. The addition ratio of reaction additives ranged from 0\\u0026ndash;40%, with an increment of 5%. The results are presented in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003e. As depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003ea, the roasting loss rate reaches its maximum value (21.2%) when the amount of reaction additives is set at 30%, indicating a complete reaction between the additives and SPL. Additionally, as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003eb, when adding a quantity of reaction additives equal to 30%, the concentration of fluoride ions increases from an initial value (4.56g/L) to a peak value (8.93g/L). This increase can be attributed to chemical transformations within crystalline structures leading to sodium fluoride formation and the subsequent influx of more fluoride ions into the solution. Furthermore, Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig6\\\" class=\\\"InternalRef\\\"\\u003e6\\u003c/span\\u003ec reveals that with increasing amounts of reaction additives, characteristic peaks corresponding to mullite and cryolite disappear while those associated with sodium metaaluminate, sodium fluoride, and nepheline become significantly enhanced; this observation suggests dissociation reactions occurring between cryolite and mullite resulting in production of sodium fluoride, nepheline, and sodium metaaluminate compounds. After conducting a comprehensive analysis, it is recommended to select an appropriate addition amount of reaction aids at approximately 30%.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec10\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e3.2 Influence of roasting temperature on the dissociation of SPL\\u003c/h2\\u003e \\u003cp\\u003eThe influence of reaction temperature on the dissolution of SPL was investigated under the conditions of a 30% additive amount and a 2-hour reaction time. The reaction temperature ranged from 700 to 850℃ with an increment of 50℃, and the results are presented in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig7\\\" class=\\\"InternalRef\\\"\\u003e7\\u003c/span\\u003e. According to the analysis depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig7\\\" class=\\\"InternalRef\\\"\\u003e7\\u003c/span\\u003ea, when the temperature reaches or exceeds 800℃, the roasting loss rate stabilizes at approximately 21%, indicating that the reaction efficiency has reached a relatively high level. Further temperature increases have minimal impact on efficiency. Simultaneously, as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig7\\\" class=\\\"InternalRef\\\"\\u003e7\\u003c/span\\u003eb, at a temperature of 800℃, the fluoride ion concentration reaches about 8.84g/L and remains stable at a high level along with the water immersion loss rate. Additionally, as observed from Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig7\\\" class=\\\"InternalRef\\\"\\u003e7\\u003c/span\\u003ec, characteristic peaks corresponding to mullite and cryolite disappear with increasing temperatures, while those associated with sodium metaaluminate, sodium fluoride, and nepheline become more prominent. Therefore, it obviously suggests that cryolite and mullite undergo dissociation to produce sodium fluoride, nepheline, and sodium metaaluminate. Based on comprehensive analysis, an appropriate reaction temperature range would be between 800\\u0026thinsp;~\\u0026thinsp;850℃.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec11\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e3.3 Influence of roasting time on the dissociation of SPL\\u003c/h2\\u003e \\u003cp\\u003eThe influence of reaction time on the dissolution of SPL was investigated under the conditions of 30% additive and a reaction temperature of 800℃. The reaction time ranged from 1 to 4 hours, with increments of 0.5 hours, and the results are presented in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig8\\\" class=\\\"InternalRef\\\"\\u003e8\\u003c/span\\u003e. As depicted in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig8\\\" class=\\\"InternalRef\\\"\\u003e8\\u003c/span\\u003ea, when the roasting time reaches 3 hours, the roasting loss rate stabilizes at approximately 21%, indicating a relatively high level of reaction efficiency. Simultaneously, as shown in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig8\\\" class=\\\"InternalRef\\\"\\u003e8\\u003c/span\\u003eb, for roasting times exceeding 3 hours, the fluoride ion concentration reaches a steady range between 8.84 g/L and 8.93 g/L while maintaining a high level along with water immersion loss rate stability. Furthermore, Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig8\\\" class=\\\"InternalRef\\\"\\u003e8\\u003c/span\\u003ec collectively reveals that mullite and cryolite characteristic peaks diminish with prolonged reaction time while sodium metaaluminate and sodium fluoride peaks become significantly enhanced alongside nepheline formation; this suggests dissociation of cryolite and mullite into sodium fluoride, nepheline, and sodium metaaluminate occurs during the process. Based on comprehensive analysis, an appropriate roasting time would be within the range of approximately 3 to 3.5 hours.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003cp\\u003eAs indicated by the aforementioned research findings, the satisfactory process conditions are as follows: a reaction additive addition ratio of 30\\u0026thinsp;~\\u0026thinsp;35%, a roasting temperature ranging from 800 to 850\\u0026deg;C, and a roasting time of 3\\u0026thinsp;~\\u0026thinsp;3.5 hours. During this process, mullite is transformed into sodium aluminium silicate while cryolite undergoes conversion into soluble sodium fluoride and sodium metaaluminate. Consequently, there is an increase in fluoride ions concentration from 4.56g/L to approximately 8.84g/L in the leaching solution, achieving the desired dissolution and dissociation effect. Sodium fluoride exhibits high solubility in water, enabling its separation from the residual material through immersion for facilitating subsequent fluoride recovery.\\u003c/p\\u003e \\u003c/div\\u003e \\u003cdiv id=\\\"Sec12\\\" class=\\\"Section2\\\"\\u003e \\u003ch2\\u003e3.4 Physical and chemical properties of reaction products\\u003c/h2\\u003e \\u003cp\\u003eUnder the experimental conditions of a 30% addition ratio of reaction additive, roasting at a temperature of 800℃ for 3 hours was conducted on the SPL mixture, followed by high-temperature roasting and water leaching experiments. The resulting leaching slag was subsequently dried. XRD and SEM-EDS analyses were performed on the roasted products and water-leaching residue, with the corresponding results presented in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig9\\\" class=\\\"InternalRef\\\"\\u003e9\\u003c/span\\u003e.\\u003c/p\\u003e \\u003cp\\u003eThe XRD patterns of the calcined clinker and water impregnated slag obtained under the optimized experimental conditions are presented in Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig9\\\" class=\\\"InternalRef\\\"\\u003e9\\u003c/span\\u003e. The disappearance of cryolite characteristic peaks after roasting indicates a chemical reaction between cryolite and the reaction additives, resulting in soluble sodium metaaluminate and sodium fluoride (Fig.\\u0026nbsp;\\u003cspan refid=\\\"Fig9\\\" class=\\\"InternalRef\\\"\\u003e9\\u003c/span\\u003ea).\\u003c/p\\u003e \\u003cp\\u003e The leaching residue was subjected to SEM-EDS analysis, as depicted in Fig.\\u003cspan refid=\\\"Fig9\\\" class=\\\"InternalRef\\\"\\u003e9\\u003c/span\\u003eb. The energy spectrum dot scan revealed a significant weakening of the F peak (Fig. \\u003cspan refid=\\\"Fig9\\\" class=\\\"InternalRef\\\"\\u003e9\\u003c/span\\u003eb) compared to Fig. \\u003cspan refid=\\\"Fig5\\\" class=\\\"InternalRef\\\"\\u003e5\\u003c/span\\u003eb, indicating dissociation of cryolite and subsequent immersion of fluorine ions in water, leading them to leave the matrix. The SEM-EDS results were consistent with those obtained from XRD.\\u003c/p\\u003e \\u003cp\\u003e \\u003c/p\\u003e \\u003c/div\\u003e\"},{\"header\":\"4. Conclusions\",\"content\":\"\\u003cp\\u003eThis study utilized SPL as the raw material and sodium carbonate as the reaction agent. The outcomes of our investigations revealed that high-temperature roasting can induce the dissolution of SPL, transforming mullite into nepheline and cryolite into soluble sodium fluoride and sodium metaaluminate. Thermodynamic calculations demonstrate that chemical reactions between mullite/cryolite and reaction additives can occur at 700\\u0026thinsp;~\\u0026thinsp;850℃, better at 800\\u0026thinsp;~\\u0026thinsp;850℃ to produce nepheline/sodium fluoride/sodium metaaluminate, respectively. In addition, under conditions of a 30\\u0026thinsp;~\\u0026thinsp;35% additive ratio with an 800\\u0026thinsp;~\\u0026thinsp;850℃ reaction temperature for 3\\u0026thinsp;~\\u0026thinsp;3.5 hours duration yields better dissociation effects on SPL while achieving complete conversion of cryolite/mullite; furthermore, increasing concentration levels of fluoride ions from clinker water immersion solution from 4.56g/L to nearly double at 8.84 g/L.\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003eCRediT authorship contribution statement \\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eFangheng Tang\\u003c/strong\\u003e:\\u0026nbsp;Experimental research, article writing. \\u003cstrong\\u003eXiping Chen\\u003c/strong\\u003e: Experimental scheme approval, data analysis, article improvement. \\u003cstrong\\u003eHao liu\\u003c/strong\\u003e: Chemical analysis. \\u003cstrong\\u003eHongwei Xuan\\u003c/strong\\u003e: Scheme formulation.\\u0026nbsp;\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eDeclaration of Competing Interest\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\n\\u003cli\\u003eVarshney, D. and K. 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Materials and Metallurgy, 2020. 19(3): p. 185-189,195, https://doi.org/10.14186/j.cnki.1671-6620.2020.03.005.\\u003c/li\\u003e\\n\\u003cli\\u003eTAN Z., et al., Analysis on the harmless treatment of aluminum electrolysis overhaul slag, Shihezi Science and Technology, 2020(1): 33-34, https://doi.org/10.3969/j.issn.1000-6532.2023. 02.025.\\u003c/li\\u003e\\n\\u003cli\\u003eNie, Y., et al., Defluorination of spent pot lining from aluminum electrolysis using acidic iron-containing solution. Hydrometallurgy, 2020. 194: p. 105319, https://doi.org/10.1016/j.hydromet. 2020.10531.\\u003c/li\\u003e\\n\\u003cli\\u003ePong T K, Adrien R J, Besida J, et al. Spent potlining\\u0026ndash;a hazardous waste made safe. Process safety and environmental protection, 2000, 78(3): 204-208, https://doi.org/10.1205/095758200530646.\\u003c/li\\u003e\\n\\u003cli\\u003eZhang Di et al, Exploring the Process of Removing Fluorine and Cyanide From Overhaul Slag. Shandong Industrial Technology, 2021(5): 9-12, https://doi.org/10.16640/j.cnki.37-1222/t.2021.05.002.\\u003c/li\\u003e\\n\\u003cli\\u003eDu Tingting et al. Study on the harmless disposal technology of toxic substances in spent potlining. Light Metals, 2020(11): 32-35, https://doi.org/10.13662/j.cnki.qjs.2020.11.009.\\u003c/li\\u003e\\n\\u003c/ol\\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\":\"info@researchsquare.com\",\"identity\":\"korean-journal-of-chemical-engineering\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"kjce\",\"sideBox\":\"Learn more about [Korean Journal of Chemical Engineering](http://link.springer.com/journal/11814)\",\"snPcode\":\"11814\",\"submissionUrl\":\"https://www.editorialmanager.com/kjce/default2.aspx\",\"title\":\"Korean Journal of Chemical Engineering\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"em\",\"reportingPortfolio\":\"Springer Subscription\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":false},\"keywords\":\"Cryolite, Baking, Dissociation, Sodium fluoride\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-4772482/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-4772482/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eThe spent pot lining of aluminum electrolysis (SPL) is a typical harmful solid waste discharged from the production process of primary aluminum. It contains about 30% of fluoride and 0.2% of cyanide, which is a valuable fluorine-containing resource. With SPL as raw material, sodium carbonate was used as a reagent, and dissociation of cryolite was investigated by baking process. Gibbs free energy of cryolite dissociation was calculated and reaction mechanism of cryolite was discussed. At the same time, the effects of reagent addition ratio, baking temperature and reaction time on the dissociation of cryolite in SPL were discussed. The results show that under the conditions of a reagent addition ratio of 30\\u0026thinsp;~\\u0026thinsp;35wt%, baking temperature of 800\\u0026thinsp;~\\u0026thinsp;850 ℃ and reaction time of 3\\u0026thinsp;~\\u0026thinsp;3.5 h, the phase of cryolite and mullite in the SPL disappears, cryolite is transformed into sodium fluoride and sodium metaaluminate compounds, and mullite is transformed into nepheline or feldspar. The concentration of fluoride ion in clinker leaching solution increased to 8.84 g/L, almost two times of primary concentration 4.56 g/L in SPL, and the effect of dissociation was obvious, which will be beneficial to the subsequent recovery of fluorides.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Study on the dissociation of cryolite in SPL\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2024-08-30 08:56:20\",\"doi\":\"10.21203/rs.3.rs-4772482/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0},{\"type\":\"reviewerAgreed\",\"content\":\"\",\"date\":\"2024-08-06T21:59:04+00:00\",\"index\":0,\"fulltext\":\"\"},{\"type\":\"reviewersInvited\",\"content\":\"\",\"date\":\"2024-08-05T13:01:45+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorAssigned\",\"content\":\"\",\"date\":\"2024-07-23T13:26:32+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"submitted\",\"content\":\"Korean Journal of Chemical Engineering\",\"date\":\"2024-07-20T05:49:10+00:00\",\"index\":\"\",\"fulltext\":\"\"}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"korean-journal-of-chemical-engineering\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"kjce\",\"sideBox\":\"Learn more about [Korean Journal of Chemical Engineering](http://link.springer.com/journal/11814)\",\"snPcode\":\"11814\",\"submissionUrl\":\"https://www.editorialmanager.com/kjce/default2.aspx\",\"title\":\"Korean Journal of Chemical Engineering\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"em\",\"reportingPortfolio\":\"Springer Subscription\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":false}}],\"origin\":\"\",\"ownerIdentity\":\"ff374b46-508f-4d14-8d5e-cf2798020844\",\"owner\":[],\"postedDate\":\"August 30th, 2024\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"published-in-journal\",\"subjectAreas\":[],\"tags\":[],\"updatedAt\":\"2025-03-10T19:54:08+00:00\",\"versionOfRecord\":{\"articleIdentity\":\"rs-4772482\",\"link\":\"https://doi.org/10.1007/s11814-025-00412-5\",\"journal\":{\"identity\":\"korean-journal-of-chemical-engineering\",\"isVorOnly\":false,\"title\":\"Korean Journal of Chemical Engineering\"},\"publishedOn\":\"2025-03-06 15:57:06\",\"publishedOnDateReadable\":\"March 6th, 2025\"},\"versionCreatedAt\":\"2024-08-30 08:56:20\",\"video\":\"\",\"vorDoi\":\"10.1007/s11814-025-00412-5\",\"vorDoiUrl\":\"https://doi.org/10.1007/s11814-025-00412-5\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-4772482\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-4772482\",\"identity\":\"rs-4772482\",\"version\":[\"v1\"]},\"buildId\":\"qtupq5eGEP_6zYnWcrvyt\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}