Degradation of α-nitroso-β-naphthol by UVA-B activated peroxide, persulfate and monopersulfate oxidants in water

Abstract

Flotation reagents, especially new chelating agents represented by α-nitroso-β-naphthol, are the main components of cobalt mining drainage. This study reports the degradation of α-nitroso-β-naphthol by simulated UVA-B (280–400 nm) activated systems using three common oxidants, hydrogen peroxide, sodium persulfate and potassium monopersulfate at a laboratory scale using a photoreactor. Parameters which can affect the degradation process were investigated and comparison of the degradation performance of the three systems were made. Based on the results, UVA-B/sodium persulfate system exhibited best performance towards the removal of α-nitroso-β-naphthol with a lower cost of oxidant and energy consumption compared to the others. The removal efficiency was found to increase as the oxidant dosage and the UVA-B power increases. Only potassium monopersulfate could be activated by bicarbonate and chloride ions, and SO4 2− has insignificant effect on the removal efficiency of α-nitroso-β-naphthol for all systems while NO3 − inhibited the degradation of α-nitroso-β-naphthol. In the UVA-B/hydrogen peroxide system, the hydroxyl radical had a leading role in the degradation of α-nitroso-β-naphthol, while in the other two systems, the degradation of α-nitroso-β-naphthol was mainly caused by the hydroxyl and sulphate radicals. Ten major intermediates from α-nitroso-β-naphthol degradation in the three oxidation systems were identified by gas chromatography and mass spectrometry. In summary, this report could be a great input in developing UVA-B activated oxidants-based treatment technologies. The UVA-B/sodium persulfate system is strongly recommended for its consideration in the treatment of mine impacted wastewaters. UVA-B/SPS is the most efficient, economical and energy-saving technique for the degradation of αNβN compared to UVA-B/HP and UVA-B/PMS systems.