Nano-scale Iron Oxide as Heterogeneous Fenton Catalyst for Organic Pollution Degradation and Heavy Metal Remediation in Water Sample of Byramangala Lake,Karnataka

Abstract

A nano-scale iron oxide (Fe₂O₃/Fe₃O₄) heterogeneous Fenton catalyst was synthesized for aqueous heavy metals remediation and was utilized to degrade organochlorine pesticides (OCPs), namely, alpha-, and delta-hexachlorocyclohexane (α-HCH and δ-HCH) as well as heptachlor epoxide (HE), in Byramangala lake water sample. Nano-scale Fe₂O₃/Fe₃O₄ was synthesized via Solution Combustion Synthesis (SCS), with glycine as fuel and iron oxide separated from raw laterite soil sample (RL) as oxidizer for the reaction. Based on detailed characterization, it was found that iron oxide constituted 34.31% of the RL sample. Later, detection of hematite (Fe₂O₃), hypersthenes (MgSiO₄) and lepidocrocite (FeOOH) in the separated fraction confirmed extraction of Fe₂O₃ fraction. Next, collection of Byramangala lake water samples and analyses of physico-chemical parameters revealed nil dissolved oxygen (DO) and high chemical oxygen demand (COD) levels. Oxidation of detected pesticides and susceptible heavy metals using the nano-scale Fe₂O₃/Fe₃O₄ was investigated under various experimental conditions: pH (3 and ~7), dosages of H₂O₂ (1-9 mM L⁻¹) and nano catalyst (0.05-0.4 g L⁻¹), as well as contact time (5-120 min) in batch experiments. Optimum values were found to be contact time of 50 mins at near-neutral pH at 5 mM L⁻¹ H₂O₂ and 0.25g L⁻¹ Fe₂O₃/Fe₃O₄ dosages, respectively. Under optimized conditions, 100% removal of both α-HCH and δ-HCH, and 99% removal of HE were observed. Furthermore, appreciable reduction in arsenic (As) and manganese (Mn) concentrations (95% and 76.6%) was also observed. Post-treatment, Fe₂O₃/Fe₃O₄ could be efficiently separated by an external magnetic field because of its ferromagnetic behaviour.