水热条件下坡缕石在NaOH溶液中的行为及结构变化

Behavior and Structural Transformation of Palygorskite in NaOH Solution under Hydrothermal Conditions

分别用1,2和3mol·L-1的NaOH溶液,在不同的温度条件下对坡缕石进行了侵蚀实验。对反应后的固相产物进行了XRD和SEM分析,对浸出液中的金属阳离子进行了原子吸收光谱分析。讨论了反应温度和碱溶液浓度对碱溶后产物的影响。XRD和SEM结果表明,cNaOH≤2mol·L-1时,坡缕石经碱溶液侵蚀后,可以生成蒙脱石和方沸石,其中反应温度的升高有利于方沸石的形成,碱溶液浓度的升高有利于蒙脱石的形成。当碱溶液浓度达到3mol·L-1,反应温度为200℃时,最终产物为SiO2。浸出液的定量分析结果显示,坡缕石与碱溶液的反应过程中,Na+对八面体阳离子的置换具有选择性,置换顺序为:Al3+>Fe3+(Fe2+)>Mg2+。

Palygorskite were treated by 1, 2, 3 mol ·L^-1 NaOH solution at various temperatures. Solid productes were characterized using XRD and SEM, and metal cations in leaching solution were assayed by atomic absorption spectrometry. The influence of reaction temperature and alkali solutions concentration on products is discussed. The results of XRD and SEM indicate that after treating by alkali solution, palygorskite will transform into montmorillonite and analcime. The increase in temperature is in favor of analcime formation, while the foramtion of montmorilloniteis is benefited by increasing the concentration of alkali solution. When the reaction is under alkali solutions concentration of 3 mol ·L^-1 and temperature of 200 ℃, SiO2 will be the only product. Quantitative analysis on metal cations in leaching solution shows that in process of palygorskite reaction with alkali solution, Na^＋ selectively replaces cations at octahedral site. The substitutional sequence is Al^3＋〉Fe^3＋（Fe^2＋）〉 Mg^2＋.