Theoretical study on the reaction of anthracene with sulfate radical and hydroxyl radical in aqueous solution

Sulfate radical (SO4 center dot(-)) and hydroxyl radical (center dot OH) generated from persulfate or peroxymonosulfate in AOPs have been widely used in contaminant degradation. Anthracene (ANT) can be decomposed by SO4 center dot(-) and center dot OH. The processes of ANT decomposition were investigated using theoretical calculations in this paper. The initiation reactions of ANT, anthrone, anthraquinone (ATQ) and 1-hydroxylanthraquinone (1-hATQ) by two radicals are studied. The highest free energy barriers of initiation reactions are 22.30 kcal mol(-1) in ATQ + SO4 center dot(-) reaction and 6.84 kcal mol(-1) in ATQ + center dot OH reaction. Comparing the rate constants of initiation reaction through the two radicals at 273-373 K, it can be concluded that SO4 center dot(-) and center dot OH both play important roles on the initiation of ANT and anthrone at lower pH. For ATQ and 1-hATQ, center dot OH is more important than SO4 center dot(-) in the initiation process, which indicates that the indirect influence of SO4 center dot(-) are more significant in the degradation processes of ATQ and 1-hATQ. This study provides theoretical confirmations for the mechanisms of reactions of ANT with SO4 center dot(-) and center dot OH, and evaluates the importance of SO4 center dot(-) and center dot OH according to the reaction rates. The work can give more insight into the degradation of PAHs by radicals.