苯并三唑在土壤中的吸附特性

为了解苯并三唑(BTA)在水-土系统中的迁移转化,通过批实验方法研究了BTA在华北平原土样(GSS13)中的吸附,考察了平衡时间、土壤投加量、溶液初始pH以及共存阳离子对吸附的影响。结果表明,在初始阶段,土壤对BTA的吸附速率较快,之后随着吸附点位的减少,吸附逐渐变慢;吸附过程符合准二级反应动力学方程。土壤对BTA的平衡吸附为非线性吸附,吸附等温线为Freundlich型;随着土壤投加量的增大,单位质量土壤吸附BTA的量减少,可能原因是所选土壤对BTA的吸附存在"固体浓度效应"。溶液的pH通过改变BTA的存在形式和土壤表面的带电性而影响吸附,当溶液pH在BTA的pKa2(8.6)附近时,土壤对BTA的吸附效果最好。此外,溶液中共存阳离子对土壤吸附BTA有不同的影响, Na+对吸附影响不明显,而不同浓度Ca2+对BTA的吸附有不同程度的促进作用。

Sorption characteristics of benzotriazole to a selected soil

To better understand the fate and transport of benzotriazole(BTA) in soil and groundwater system,in this study,batch experiments were conducted to investigate the sorption of BTA to a Chinese reference soil(GSS13).The effects of equilibrium time,soil dosage,pH value,and coexisting cations on sorption were investigated.The results show that the sorption of BTA to the soil is fast at the beginning stage and becomes slowly due to the decrease of sorption sites.The sorption process follows pseudo-second-order kinetic equation.The sorption of BTA to the soil is nonlinear.The Freundlich isotherm fitted the BTA sorption data very well.The amount of BTA absorbed in the soil reduced with the increase of soil dosage,which probably was caused by the particle concentration effect.The solution pH affects sorption through influencing the form of BTA and the charge on the surface of soil.The maximum sorption of BTA to the soil is observed when the solution pH value is around pKa2(i.e.,8.6) of BTA.The influence of coexisting cations on BTA sorption to the soil is different.The influence of Na+ on BTA sorption to the soil is not obvious.However,Ca2+ promotes BTA sorption to the soil and the promoting effect is dependent on concentration of Ca2+ ion.