Theoretical investigation on the degradation of dibutyl phthalate initiated by •OH and SO4•- in aqueous solution: Mechanism, kinetics and ecotoxicity assessment

Phthalate esters and their (OH)-O-center dot-addition products are considered to pose health risks to aquatic organisms. In this work, the aquatic conversion mechanism, kinetics and ecotoxicity assessment of dibutyl phthalate were studied in a theoretical way. The results from the initial reaction of dibutyl phthalate by (OH)-O-center dot and SO4 center dot- show that the H-abstraction occurring in -COOC4H9 groups is the principal channel. Based on thermodynamic calculations, the rate constants of aquatic initial reaction induced by (OH)-O-center dot and SO4 center dot- were obtained at 298 K. These values are 1.93 x 10(9) M-1 s(-1) and 1.36 x 10(8) M-1 s(-1), respectively, which are in agreement with the experimental results. The initial degradation ratios show that 'OH exhibits higher universality than SO(4)(center dot- )in the ultraviolet/persulfate process. The toxicity assessment for this system was preformed using ECOSAR software based on compound chemical structures. Compared with SOZ-addition intermediates, (OH)-O-center dot-addition intermediates have more ecological risk to sensitive aquatic organisms. Therefore, more attentions should be paid to the (OH)-O-center dot-initiated transformation of dibutyl phthalate in the future experimental works.