Effects of humic acid fractions with different polarities on photodegradation of 2,4-D in aqueous environments

Abstract

Four fractions (A, B, C, and D) of humic acids (HAs) were separated based on the polarity from weak to strong. UV-vis absorption and Fourier transform infrared spectroscopy (FTIR) analysis show that the fractions C and D possessed more aromatic C=C content. The influences of HAs and their fractions on the photolysis were investigated by the photodegradation of 2,4-D solutions under simulated solar light irradiation. The degradation rate of 2,4-D was found to decrease in the presence of bulk HAs or their fractions especially at high HAs concentration. The fractions of strong polarity C and D retarded the degradation rate more than the fractions of weak polarity A and B. This could be attributed to the different absorption intensity of the four HAs fractions in the order of D ≥ C > A > B, and the stronger ?-? electron donor-acceptor interactions between the strong polar fractions and 2,4-D.

Keywords

humic acids (HAs) / fractions / 2,4-dichlorophenoxyacetic acid (2,4-D) / photodegradation