Degradation of Humic Acid by Ferrous Ion Activated Persulfate

Abstract

The persulfate anions (S2O8 2™) can be activated by Fe2+ to produce sulfate radicals (·SO4 −) and hydroxyl radicals (·OH), which can oxidize organic compounds rapidly. Humic acid (HA) is widely found in nature and is the main limiting factor for high-concentration wastewater discharge. In this study, HA was treated by Fe2+/S2O8 2™ system, the effects of initial pH, concentrations of Fe2+, persulfate (PS), and HA on the removal efficiencies of HA and E3/E4 were discussed. Besides UV254 and UV280, we found that UV250, UV270, UV300, UV365, UV400, UV436 and UV465 can effectively quantified the concentrations of HA, providing more HA characterization methods. When the initial pH was 3.0, the concentrations of PS and Fe2+ were 100 mmol/L and 20 mmol/L, respectively, the removal efficiency of HA reached 72% after 5 minutes, indicating that PS/Fe2+ effectively degrade HA, and E3/E4 increased from 2.6 to 5.75, suggesting the molecular weight and aromaticity of HA decreased. The removal efficiencies of HA increased as the concentrations of Fe2+ and PS increased, while the removal efficiencies of HA decreased as the initial concentration of HA increased. The addition of hydroxylamine hydrochloride (HAH) in Fe2+/S2O8 2™ system, could effectively promoted the Fe3+/Fe2+ circulation and reduced the accumulation of Fe3+, and strengthened the removal efficiency of HA. The research results indicate that Fe2+/S2O8 2™ oxidation is a promising technique for the treatment of HA in wastewater.