季胺盐化合物在水稻土中的吸附与淋溶行为

Sorption and Leaching Behaviors of Quaternary Ammonium Compounds in Paddy Soil

通过吸附批处理实验及土柱淋溶实验,探讨了3种典型季胺盐化合物(QACs)十二烷基三甲基氯化胺(DTAC)、十六烷基三甲基溴化胺(CTAB)及双十二烷基二甲基氯化胺(DDAC)在水稻土中的吸附和淋溶行为。结果表明,QACs(20 mg·L-1)的吸附过程符合拟二级动力学方程(R2>0.995),其有机碳分配系数(Koc)为3056~36 245 m L·g-1,与其分子量及碳链长度显著正相关(P<0.01),即其吸附性能强弱为DDAC>CTAB>DTAC。DDAC和CTAB为易吸附型污染物,DTAC为中等吸附型污染物。中性淋溶条件(p H=7)下,QACs(20 mg·kg-1)难被淋溶,土柱淋溶率为27%~41%,与其分子量及碳链长度显著负相关(P<0.01);酸性淋溶(p H=4)及去除土壤有机质条件下,QACs的淋溶能力均大幅提高,土柱淋溶率分别为42%~63%及58%~74%。

Sorption and leaching behaviors of three typical quaternary ammonium compounds(QACs), i.e. dodecyl trimethyl ammonium chloride(DTAC), cetyl trimethyl ammonium bromide(CTAB), and didecyl dimethyl ammonium chloride(DDAC), in paddy soil were investigated using batch sorption and soil column leaching experiments. Sorption kinetics of three QACs followed pseudo-second-order kinetics.The organic carbon partition coefficients(Koc)of these QACs, ranging from 3056 m L·g-1 to 36 245 m L·g-1, had significantly positive relationship with their molecular weight and carbon chain lengths, indicating that the sorption of QACs decreased in order of DDAC >CTAB >DTAC. DDAC and CTAB were pollutants with high sorption abilities, while DTAC with moderate sorption ability. In leaching water of p H7,three QACs had low leaching abilities, with leaching rates ranging from 27% ~41% and being negatively correlated with their molecular weight and carbon chain lengths. Migration of three QACs(20 mg·kg-1)significantly enhanced in acidic leaching water(p H=4)and organic matter-removed paddy soil, with leaching rates ranging from 42%~63% and 58%~74%, respectively.