有机粘土和粘土对p,p’-DDE的吸附/解吸研究

Adsorption and desorption of p,p’-DDE on natural and HDTMA modified clays

采用批量平衡实验,研究阳离子表面活性剂十六烷基三甲基铵离子(HDTMA)改性的zeo-HDTMA(有机沸石)、mont-HDTMA(有机蒙脱土)和atta-HDTMA(有机凹凸棒土)及其原粘土对典型有机氯农药DDT代谢产物p,p’-DDE的吸附解吸特性。结果表明,随原粘土阳离子交换容量(CEC)的增大,有机粘土吸附量增大,且有机粘土的吸附量比原粘土大大提高;有机粘土和原粘土对p,p’-DDE的吸附能力顺序为:zeo-HDTMA>mont-HDTMA>atta-HDTMA≥mont(蒙脱土)>atta(凹凸棒土)>zeo(沸石),这一顺序与它们的有机碳质量分数大小顺序一致。原粘土对p,p’-DDE的吸附等温线符合Langmuir吸附等温方程,吸附呈单分子层形式,且存在竞争吸附;有机粘土对p,p’-DDE的吸附等温线符合Linear吸附等温方程,吸附是p,p’-DDE在有机粘土中有机相的分配所致。当CaCl2质量浓度从0增加到50g/L时,mont-HDTMA对p,p’-DDE吸附量提高了10.3%。有机粘土和原粘土对p,p’-DDE的解吸率大小顺序为:zeo>atta>mont>atta-HDTMA>mont-HDTMA>zeo-HDTMA,这一顺序与它们的有机碳质量分数大小顺序相反。

Batch equilibrium isotherm runs were performed to measure the removal capacities of 6 natural and HDTMA modified clay samples for p,p＇-DDE （a metabolite of pesticide DDT） and its release under desorption conditions. The removal capacities of the modified clays were much higher than those of the corresponding natural clays the capacity order was the same as the sample＇s organic carbon content and also consistent with the cation exchange capacity of the natural clays： zeo-HDTMA〉mont-HDTMA〉atta-HDTMA≥mont〉atta〉zeo. Experimental data for the natural clay runs were well represented by the Langmuir isotherm model, suggesting that monolayer adsorption was the mechanism for p,p＇-DDE removal. The linear relationships for p,p＇-DDE in the liquid and solid phases indicates that partition was the mechanism for the distribution patterns observed in the organic modified clay runs. The most well adsorbed DDE was least ready to come out of the clay sample as evidenced by the desorption order of zeo〉att〉mont^atta-HDTMA〉mont-HDTMA〉zeo-HDTMA. Presence of CaCl2 at 50 g/L the capacity of mont-HDT- MA increased by 10.3%.