凹凸棒石和海泡石对镉离子的吸附效果

摘要

Effects of attapulgite and sepiolite adsorbing Cd2+ in aqueous solutions relative to initial concentration, solid⁃liquid ratio, exposure duration, and pH were investigated through a static batch experiment under a set NaNO3 ionic strength (0�01 mol·L-1). Results show that, under the set NaNO3 ionic strength, Cd2+ adsorption of sepiolite and at⁃tapulgite of high grade and attapulgite of low grade is positively related to initial concentration of Cd2+ in the solution, but negatively to solid⁃liquid ratio of the solution. Fitting with the Langmuir isothermal adsorption equation reveals an order of high grade attapulgite ( 33�67 mg·g-1 )>high grade sepiolite ( 25�55 mg·g-1 ) >low grade attapulgite( 11�52 mg·g-1 )>low grade sepiolite (5�24 mg·g-1) in terms of theoretical saturated Cd2+adsorption;Cd2+adsorption on sepiolite and at⁃tapulgite is strongly influenced by pH of the solution, and peaks when pH is 2-4; Cd2+ adsorption on attapulgite is rela⁃tively stable and reaches equilibrium basically in 3 h;in solutions 0�01 mol·L-1 NaNO3 in ionic strength, 625 mg·L-1 in initial Cd2+ concentration, 15 g·L-1 in clay mineral addition amount and 2-4 in pH, the minerals display an order of high grade sepiolite> high grade attapulgite> low grade attapulgite>low grade sepiolite in terms of Cd removal efficiency.%采用静态批试验方法研究了凹凸棒石和海泡石对溶液中Cd2＋的吸附特性，并通过考察一定离子强度下，不同初始浓度、固液比、吸附时间和pH值对吸附镉的影响。结果显示：在0�01 mol·L－1 NaNO3离子强度下，高品位海泡石、凹凸棒石和低品位凹凸棒石对溶液中Cd2＋的吸附量与初始浓度呈正比，与固液比呈反比；根据Langmuir等温吸附方程拟合结果，在给定离子强度25℃条件下黏土矿物Cd2＋的理论饱和吸附量从大到小依次为高品位凹凸棒石（33�67 mg·g－1）、高品位海泡石（25�55 mg·g－1）、低品位凹凸棒石（11�52 mg·g－1）和低品位海泡石（5�24 mg·g－1）；Cd2＋在海泡石、凹凸棒石上的吸附受pH值的影响较大，在pH值为2～4时吸附效果最好；凹凸棒石对Cd2＋的吸附较为稳定，在3 h时基本达到吸附平衡；在离子强度为0�01 mol·L－1 NaNO3、Cd2＋初始浓度为625 mg· L－1、黏土矿物添加量为15 g·L－1和pH值为2～4时，去除效果从大到小依次为高品位海泡石、高品位凹凸棒石、低品位凹凸棒石和低品位海泡石。