Performance evaluation of advanced Fe°/Fe+2/Fe+3/H2O2 process in the reduction of nitrate and organic matter from aqueous solution

Abstract

Today, global concerns about nitrate and organic matter in water and its adverse impact on health have increased. This study aims to investigate the use of nZVI technology for nitrate reduction and the use of Fe2+, Fe3+/H2O2 technology for COD removal, simultaneously. Different factors that influence the reaction of nitrate with nZVI and COD removal were investigated. These included nZVI, Fe2+ and Fe3+ dosages (1–10 mg/L), initial nitrate concentration, initial solution pH (2–10), H2O2 concentration (30–250 mg/L), and treatment duration (10–90 min). At [Fe°] = 2.5 mg/L, 81–90% nitrate removal efficiencies were observed for initial [NO3−] ranging from 20 to 200 mg/L. At [Fe°] = 1, 2.5, 5, and 10 mg/L, 22, 26, 39.5, 77.5, and 70% COD removal efficiencies were observed for reaction time 60 min and initial COD 520 mg/L. When the initial pH values were 2, 4, 6, 8, and 10, the nitrate removal efficiency was approximately 82, 93, 68, 60, and 40%, respectively, with nZVI. COD degradation percent at pH 10 is approximately 28%, whereas at pH 6, removal efficiency reaches to 77.6% after 60 min reaction time. Based on the results, the optimum pH for nitrate reduction is 4 whereas for COD degradation is 6. The reduction capacity for nitrate increases with increasing time and nZVI dosage but decreases with the increase in initial concentration of nitrate and pH values.