Intrinsic mechanisms of calcium sulfite activation by siderite for atrazine degradation

Abstract

Employing sulfite to produce SO4−has drawn increasing interests. However, the excess amount of aqueous SO32−quenches the SO4−when utilizing Na2SO3 as the sulfite resources. The present study evaluated the degradation performance with atrazine (ATZ) as a model substance in the siderite/sulfite process by replacement of Na2SO3 with CaSO3. The results show that the present system works effectively towards ATZ degradation at an initial pH of 6, and the siderite/CaSO3 system performs much better than the siderite/Na2SO3 system due to the low solubility of CaSO3. An increase in siderite concentration slightly increases the degradation rate constant for ATZ. However, the change in CaSO3 dosage from 2 to 10 mM greatly decreases the ATZ degradation rate constant from 0.067 ± 0.003 min−1 to 0.021 ± 0.002 min−1. Based on the identified intermediate products, the possible ATZ degradation pathways were proposed. In addition, natural siderite can be used in the present system. Based on the facts that lots of research were performed with Na2SO3 to generate reactive species and the Ca2+ ion possesses some unique functions such as promoting the dewatering of activated sludge, the present research into CaSO3 activation can greatly advance our understanding of the mechanisms involved in sulfite activation and its further applications in wastewater treatment.