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

Sulfate radical (SO₄^-) and hydroxyl radical (OH) generated from persulfate or peroxymonosulfate in AOPs have been widely used in contaminant degradation. Anthracene (ANT) can be decomposed by SO₄^- and 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^- reaction and 6.84 kcal mol^-1 in ATQ + OH reaction. Comparing the rate constants of initiation reaction through the two radicals at 273-373 K, it can be concluded that SO₄^- and OH both play important roles on the initiation of ANT and anthrone at lower pH. For ATQ and 1-hATQ, OH is more important than SO₄^- in the initiation process, which indicates that the indirect influence of SO₄^- 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^- and OH, and evaluates the importance of SO₄^- and OH according to the reaction rates. The work can give more insight into the degradation of PAHs by radicals.