Comparative removal of imidacloprid, bisphenol‐S, and azithromycin with ferrate and FeCl3 and assessment of the resulting toxicity

Abstract

AbstractBACKGROUNDEmerging micro‐pollutants (EMPs) in water have received much attention due to their potential hazards to human health and ecological security. Ferrate has been researched in recent years to remove both particulate and dissolved impurities (including EMPs) from water, and its promising performance has been attributed to the high oxidation capacity and coagulation functions. However, limited research has compared ferrate with coagulation alone in the treatment of EMPs, which is one of the major objectives of this study.RESULTSThree emerging micro‐pollutants (EMPs), imidacloprid (IMP), bisphenol‐S (BS), and azithromycin (AZM) were chosen for this study. In all cases, ferrate outperformed to ferric chloride in the removal of the EMPs. For a given ferrate dose of 0.05 mM, 99% of BS, 85% of AZM, and 78% of IMP were removed for a start concentration of 10 μg L−1. However, if the start concentration was 1000 μg L−1, removal efficiency was decreased to 82% for BS, 62% for AZM, and 22% for IMP. pH 5 was favorable to the EMP removal by ferrate for the study conditions. Although higher removals of IMP, BS, and AZM were achieved by ferrate in comparison to those by ferric chloride, only 20% DOC removal was achieved by the ferrate. The formation of various oxidation products in the degradation process resulted in the disparity of the solution toxicity; that of BS was reduced but those of IMP and AZM increased after ferrate treatment. Nevertheless, the toxicity of ferric chloride treated samples was all increased.CONCLUSIONFerrate has higher efficiency comparing with FeCl3 to remove IMP, BS, and AZM. Degradation of the EMPs by ferrate was more efficient in acidic conditions (pH 5) and at the EMPs' lower initial concentrations for the given conditions. IMP was more resistant to the ferrate treatment compared to BS and AZM under the same conditions. Overall, 20% DOC reduction was achieved by ferrate for pH 5. Finally, the toxicity of BS can be reduced but those of IMP and AZM were increased after ferrate treatment, whilst the toxicity of ferric chloride treated samples was all increased. © 2020 Society of Chemical Industry