偏高岭石碱溶合成方钠石相变过程及吸附特性

方钠石具有笼型结构和比表面积大的特性,使其吸附能力较强。以偏高岭石和NaOH为原料,通过碱溶法合成了羟基方钠石,探讨了NaOH浓度、反应温度、反应时间和液固比对合成方钠石的影响。采用XRD、SEM、IR和NMR对碱溶过程的产物进行了表征；探讨了方钠石对Al³⁺的吸附特性。结果表明,反应温度对方钠石合成影响最大,NaOH浓度次之,液固比影响较小,升高反应温度和增大NaOH浓度可缩短反应时间。碱溶过程中,偏高岭石中的活性铝、硅优先溶解于NaOH溶液,随着反应的推进,溶液中的铝、硅达到一定浓度后会发生缩聚反应形成前驱体胶凝相。NaOH浓度对前驱体胶凝相的转变影响显著,低浓度时,胶凝相主要转变成沸石相；高浓度时则转变为方钠石相,反应的本质是处于亚稳定状态的沸石相与NaOH反应形成方钠石相。吸附特性试验表明,方钠石对Al³⁺的吸附符合Langmuir模型,其吸附率高达99.9%,最大吸附量达89.77 mg/g。

Phase Transformation Process and Adsorption Characteristics of Sodalite Synthesis by Metakaolinite Alkaline Leaching

Thanks to its high cagelike structure and specific surface, sodalite exhibit strong adsorption capacity. In this study, the hydroxysodalite was synthesized by alkali leaching with metakaolinite and NaOH as raw materials, and the impact of NaOH concentration, reaction temperature, reaction time and liquid to solid ratio on the synthesized sodalite was discussed. Furthermore, the product in alkali dissolving process was characterized by XRD, SEM, IR and NMR, and the adsorption properties of sodalite to Al³⁺ were analyzed. The results indicated that the reaction temperature showed the most notable impact on the synthesis of sodalite, followed by NaOH concentration, and the impact of liquid to solid ratio was the least. With the temperature and the concentration of NaOH increasing,the reaction time can be reduced. During the alkali leaching process, the active aluminum and silicon of metakaoli-nite would be dissolved in NaOH at first. With the advance of reaction, polycondensation would take place to form the precursor gelatinization phase when the aluminum and silicon reached a certain concentration in the solution. The concentration of NaOH played a significant role in the transformation of precursor gelatinization phase, the gelatinization phase would mainly transform to zeolite phase at low concentration, while sodalite phase at high concentration. The essence is that zeolite phase in metastable state would react with NaOH and transform to sodalite phase. The experiment of adsorption characteristics indicated that the adsorption of sodalite to Al³⁺ conformed to Langmuir model, with the maximum adsorption rate of 99.9% and maximum absorption capacity of 89.77 mg/g.