碱性盐化条件下蒙脱石和伊利石对镉的吸附特征研究

Adsorption Behaviors of Cd on Montmorillonite/Illite in Alkaline Saline Conditions

通过吸附试验方法研究了碱性条件下蒙脱石和伊利石对镉的吸附特征以及可溶性无机盐对蒙脱石和伊利石吸附镉的影响。结果表明,碱性条件下两种粘土矿物(蒙脱石和伊利石)对镉的吸附行为受pH值、镉离子初始浓度、两种粘土矿物用量及反应时间等因素的影响;pH值对蒙脱石和伊利石吸附镉影响显著,当pH值从7增加到9时,蒙脱石和伊利石对镉的吸附量分别由5.26mg·g-1和3.84mg·g-1增加到7.24mg·g-1和7.02mg·g-1;随着两种粘土矿物用量的增加,相对吸附量有降低的趋势;吸附量随着反应时间的增加而增大,当反应时间超过6h,吸附量不再增加,吸附趋于平衡。在pH9时,可溶性无机盐阳离子对粘土矿物的影响较大:同种无机盐阳离子对粘土矿物解吸镉的影响随着浓度的增加而增大,不同无机盐阳离子在相同浓度条件下,对粘土矿物解吸镉的影响依次为氯化铵>氯化钙>氯化钾>氯化钠;可溶性无机盐阴离子对粘土矿物解吸镉的影响复杂,氯化钠、硝酸钠促进蒙脱石和伊利石对镉的解吸,碳酸钠、磷酸钠、硫酸钠由于阴离子与镉离子结合产生沉淀,最终促进了对蒙脱石和伊利石对镉吸附。

Cadmium adsorption features by montmorillonite and illite in alkaline saline conditions were studied by experiment to study mechanism of the biologic validity of eadmium in alkaline saline soils in western shore of Bohai Sea. The cadmium adsorption equilibrium time was 6 hours when the pH values in initiative solutions were 9, and the adsorption cadmium capacity by montmorillonite was 6.910 mg·g^-1 while the adsorption capacity of cadmium by illite was 6.642 mg·g^-1. when the quantity ratio between adsorbent and cadmium in initiative reaction solutions was 15×10^3, the adsorption effect was best. The cadmium adsorption capacity increased with the increase of pH values from 7 to 10. When there were inorganic salts in the solutions of which the pH values in initiative solutions were 9, cadmium adsorption capacity by montmorillonite and illite changed pronouncedly. Taking ehloride for example, the influence of cations on adsorption cadmium strengthened with inorganic salts coneentrations increased in the solutions; when the cations concentrations were same, and the orders of cations influencing on adsorption effect were NH4＋〉Ca^2＋〉Na^＋〉K^＋;Taking sodium salt for example, the influence of anions in alkaline conditions were complicated： Cl^-, NO3^- decreased cadmium adsorption capacity while CO3^2-, PO4^3-, SO4^2- increased adsorption eadmium capacity by precipitation adsorption.