Relation between polarity of humic acid and adsorption of organic pesticides
腐殖酸极性与有机农药吸附行为的关系

Humic acid (HA) was structurally 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 resulted 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 Kd of organic pesticides on HA decreased with increasing polarity of HA.