Abstract
This study investigates the generation of hydroxyl radicals (˙OH) in a peroxymonocarbonate (PMC)-based advanced oxidation process (AOP) catalyzed by Co(2+). Steady-state ˙OH concentrations ([˙OH](ss)) were quantified using terephthalic acid (TA) as a probe. The presence of PMC alone had negligible effect on ˙OH production, whereas Co(2+) markedly enhanced radical formation. Specifically, [˙OH](ss) increased from 4.03 × 10(-17) M in the H(2)O(2)-only system to 2.25 × 10(-16) M in H(2)O(2) + Co(2+), and from 2.26 × 10(-17) M in PMC-only to 3.38 × 10(-16) M in PMC/Co(2+). This enhancement is attributed to a Fenton-like mechanism involving Co(2+). Kinetic analysis revealed first-order dependence on TA concentration (R (2) ≈ 0.99), Langmuir-type dependence on PMC concentration, and linear correlation with Co(2+) concentration. Inorganic anions exhibited diverse roles, with Cl(-) enhancing ˙OH generation by ∼26%, whereas SO(4) (2-) and HPO(4) (2-) suppressed it by ∼35 and ∼25%, respectively. A kinetic model describing radical generation agreed well with experimental data, offering valuable mechanistic insights and highlighting practical applicability of PMC-based AOPs for controlled ˙OH generation.