Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi 110012, India.
Bull Environ Contam Toxicol. 2013 Jul;91(1):111-6. doi: 10.1007/s00128-013-1012-9. Epub 2013 Jun 1.
Removal of mixed pesticides, namely alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, β-endosulfan, p,p'-DDT and two metabolites p,p'-DDE and endosulfan sulphate from aqueous solution by batch adsorption onto three commercial organo-modified montmorillonite clays [modified with octadecylamine (ODA-M), modified with dimethyl- dialkylamine (DMDA-M) and modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M)] were investigated. Effect of process variables, mainly contact time and initial concentration of mixed pesticides, on adsorption phenomenon were evaluated. To understand the adsorption kinetic pseudo-first-order and pseudo-second-order models were tested. The pseudo-second-order model provided the best fit for explaining adsorption kinetics, on the basis of high correlation coefficient (r) and normalized percent deviation values. The adsorption equilibrium was explained by the Freundlich isotherm (r = 0.951-0.992). High values (0.17-0.52 mg g⁻¹) of Freundlich constant (K(f)) indicated higher affinity of pesticides towards all three organoclays, as a result of hydrophobic interaction between the adsorbent/adsorbate systems. Pesticides with high octanol-water partition coefficient (K(ow)) and low water solubility showed faster adsorption with higher K(f) values as compared to the pesticides with low K(ow) and high water solubility. The order of organoclays for removal efficiency of mixed pesticide was ODAAPS-M > DMDA-M > ODA-M. These findings may find application to decontaminate or treat mixed pesticide contaminated industrial/agricultural waste waters.
采用批式吸附法研究了三种商业有机改性蒙脱石黏土（十八烷基胺改性（ODA-M）、二甲基二烷基胺改性（DMDA-M）和十八烷基胺与氨丙基三乙氧基硅烷改性（ODAAPS-M））从水溶液中去除混合农药（即甲草胺、乙草胺、氯吡磷、氟虫腈、α-硫丹、β-硫丹、p,p'-DDT 和两种代谢物 p,p'-DDE 和硫丹硫酸盐）。考察了工艺变量（主要是接触时间和混合农药的初始浓度）对吸附现象的影响。为了理解吸附动力学，测试了伪一级和伪二级动力学模型。基于高相关系数（r）和归一化百分偏差值，伪二级模型为解释吸附动力学提供了最佳拟合。吸附平衡由 Freundlich 等温线解释（r = 0.951-0.992）。Freundlich 常数（K(f)）值较高（0.17-0.52 mg g⁻¹）表明农药对所有三种有机黏土具有较高的亲和力，这是由于吸附剂/吸附物体系之间的疏水相互作用所致。与具有低 K(ow)和高水溶性的农药相比，具有高辛醇-水分配系数（K(ow)）和低水溶性的农药具有更快的吸附速度和更高的 K(f)值。混合农药去除效率的有机黏土顺序为 ODAAPS-M > DMDA-M > ODA-M。这些发现可能适用于净化或处理受混合农药污染的工业/农业废水。
