疏水性腐植酸酯醚的制备及其对草枯醚农药水污染的修复机制

Preparation of hydrophobic Humic Acid Ester Ether (HAEE) and its mechanisms of the remediation for chlornitrofen

摘要:

草枯醚作为一种二苯醚类除草剂，曾在20世纪70~90年代大量使用，是一种典型的持久性有机污染物. 禁用20年来，其在水、土壤环境中仍有检出，严重威胁农业生态安全. 实验采用缩水甘油醚对前期制备的腐植酸酯（HAE）进行化学改性，调控合成强疏水性的腐植酸酯醚（HAEE）吸附材料，用于水中草枯醚吸附去除. 通过傅里叶红外光谱表征、疏水角测定，可以表明HAEE不仅保留了芳香核和类酯结构，同时疏水角由改性前的30°提高到96°. 此外，通过HAEE对水中草枯醚的吸附行为，探究HAEE对水中草枯醚农药污染的修复机制，结果表明：HAEE对草枯醚的吸附量随疏水性的增强而增大；吸附在2.0 h即达平衡；并符合Lagergren二级动力学方程；吸附等温线契合Freundlich模型； HAEE经5次再生后，对草枯醚的去除率仍在78%以上. HAEE对草枯醚的吸附机制以疏水分配和π-π作用为主. 实验制备的疏水性HAEE对草枯醚的吸附，可为水、土壤环境中草枯醚的污染修复提供理论依据.

Abstract:

Chlornitrofen is a diphenyl ether herbicide, which is a typical persistent organic pollutant and has been widely used in 70~90 years in twentieth Century. Although it has been banned for 20 years, chlornitrofen still exists in water and soil systems, which has the potential threats to the agro-ecology systems. In the present study, humic acid ester ether (HAEE) was synthesized via regulating the dosage of glycerol triglycidyl ether while humic acid ester (HAE) was uniting as raw material. HAEE was analyzed by the analysis methods of Fourier transform infrared spectroscopy and contact angles. The results indicated that hydrophobic HAEE has the structure of humic acid and the characteristic functional groups of HAE. The adsorption characteristics and mechanisms of HAEE to chlornitrofen were investigated via a series of batch equilibrium experiments. As the results showed, the hydrophobic angle is increased from 30 to 96 degrees before modification. The degree of hydrophobic of HAEE is positively correlated with the adsorption capacity of chlornitrofen, and equilibrium reached after 2.0 h. The kinetics of adsorption is described well by the pseudo-second-order model, and Freundlich models are more suitable for the sorption isotherm. The adsorption capacity reduces gradually after 5 cycles. The removal rate is still above 78%. The adsorption mechanisms are π-π interaction and hydrophobic distributional effects. Adsorbent prepared by this method may provide a novel approach for remediation of chlornitrofen in aqueous-soil environment.