The effect of humic acid on oxidative degradation of anthracene using cobalt ion-activated peroxymonosulfate

Anthracene (ANTH) is a difficult to degrade polycyclic aromatic hydrocarbon that can find its way into water bodies through the food chain. In this study, oxidative degradation of anthracene (ANTH) in aqueous solution was undertaken using cobalt ion activated peroxymonosulphate (PMS) that relies on the action of strongly oxidizing sulphate radical anion (SO 4 − ) and hydroxyl radical ( OH). Following the often-reported tendency of natural organic matter to interfere with water treatment interventions, the effect of humic acid (HA) on the oxidative degradation process and efficiency was assessed as well. Results obtained show clearly that Co-activated PMS was very efficient for the degradation of ANTH in water, with complete degradation achieved within 90 min. Degradation was achieved following a 3-stage profile, involving an initial rapid degradation stage, an intermediate slower step and a final steady state degradation state. HA manifested both beneficial and adverse effects on ANTH degradation, modifying the 3-stage degradation mechanism, delaying the process, but not necessarily the final outcome of complete degradation. The local reactivity of ANTH molecule was modelled via quantum chemical computations, which enabled identification of electron-rich regions on the molecule, where attack by oxidizing species would be initiated. This study has shown that the PMS/Co oxidation process is effective for treating anthracene contaminated water, even in the presence of natural organic matter.