腐殖酸极性与有机农药吸附行为的关系

Relation between polarity of humic acid and adsorption of organic pesticides

用不同的方法对腐殖酸(HA)进行了结构改性处理,并用元素分析仪、红外光谱仪和电位滴定仪对改性前后的HA进行了表征;通过振荡平衡法,研究了HA改性前后对有机农药甲基对硫磷、西维因、克百威的吸附行为.结果表明,水解处理使得HA的碳水化合物结构减少,肟化处理使得HA的CN结构增加,氧化处理使HA的芳香环发生开环反应、—COOH基团增加,肟化和氧化处理均使得HA极性增强;有机农药甲基对硫磷、西维因、克百威通过分配作用吸附于HA,分配系数Kd与HA有的机碳含量成正比,HA的极性越强,吸附量越小.

Humic acid （HA） was strocturally modified using acid hydrolysis, oximation and oxidation. The elemental analysis, fourier transform infrared spectrometry （FTIR） and potentiometric titration were used to obtain structural and compositional information of the three modified HAs. Then sorption of organic pesticides parathion - methyl, carbaryl or carbofuran on the HA was examined in batch sorption experiments. Acid hydrolysis removed carbohydrates from HA ; oximation made HA produce more oxime （ C = N ） groups ; and oxidation resuhed in a ring cleavage reaction in the HA which produced more carbonyl （ - COOH） groups, Both oximation and oxidation increased HA polarity. Since the sorption of organic pesticides on modified HAs appeared to take place more by a partition, the sorption coefficients Kd of organic pesticides were proportional to the organic carbon content of HA. And it was observed that the Ka of organic pesticides on HA decreased with increasing polarity of HA.