碳酸化对黏土质白云岩热分解产物去除水中镉离子的影响

Effect of Carbonation on Removal of Cadmium Ions in Aqueous Solution by Decomposed Clayey Dolomite

以黏土质白云岩为原料经煅烧、碳酸化处理后,研究固液比、溶液初始pH值、反应时间、初始浓度等因素对其去除镉离子效果的影响,并对去除机理进行了探讨。结果表明:随着固液比增大,溶液中镉离子浓度先降低然后趋于稳定;煅烧-碳酸化黏土质白云岩(CCCD)去除水中镉离子受溶液初始pH值的影响较小,对不同初始pH值的镉溶液都有较好的处理效果。动力学数据表明,镉离子的去除符合准二级动力学方程(R^2≥0.996);Langmuir等温吸附模型更好地描述CCCD对镉离子的去除过程;热力学结果表明吸附类型是化学吸附。CCCD去除水中镉离子的主要作用机理是方镁石缓慢与水反应生成氢氧化镁,氢氧化镁电离产生氢氧根,使溶液的pH值升高,诱导镉离子水解,进而形成表面沉淀。

A product derived from the decomposition of clayey dolomite was carbonated, which was used to remove Cd2＋ in aqueous solution. The effects of soild-liquid rate, initial pH value, contact time, initial concentration on the removal efficiency of cadmium ions were investigated. The removal mechanism was discussed. The results show that the concentration of cadmium decreases and then becomes stable with the increase of soild-liquid ratio. The initial pH value of solution has a slight effect on the removal efficiency of cadmium ions by calcination-carbonation clayey dolomite （CCCD）. The removal kinetic of cadmium ions follows the pseudo-second-order model （R2≥0.996）. The Langmuir isothermal model can describe the removal process of cadmium ions by CCCD. The thermodynamic results reveal that the adsorption belongs to chemical adsorption. The main mechanism of removing cadmium ions in aqueous solution by CCCD is since magnesium oxide slowly reacts with water to produce magnesium hydroxide, and the reaction results in the increase of the solution pH value, inducing the hydrolysis of cadmium ions to produce the surface precipitation.