Enhanced Removal Of Complex Nickel By Microelectrolysis Of Iron-based Nanomaterials Coupled With Fenton Oxidation

Ethylenediaminetetraacetic acid（EDTA）is a strong complexing agent,which is widely used in the electroplating nickel process of the printed circuit board industry.EDTA can form a very stable complex with nickel ions,Ni-EDTA,which is difficult to remove by conventional chemical precipitation methods.Due to the high toxicity of EDTA and the significant affinity of EDTA to Ni,and it is not biodegradable,the persistence of Ni-EDTA will amplify its environmental hazard effects.Nickel in wastewater will have a negative impact on the ecological environment and human health through bioconcentration and biomagnification.Therefore,there is an urgent need to develop effective removal methods.This paper proposes a new method to treat Ni-EDTA complex wastewater—firstly degrade the complex through the microelectrolysis-Fenton process,and then remove nickel ions through chemical precipitation.The process and mechanism of three iron-based nanomaterials for direct removal of Ni-EDTA were studied.When the initial concentration of nickel is 20 mg/L,the initial p H of the solution is 6,and the dosage of iron-based nanomaterials is 300 mg/L,nano zero valent iron,nano iron carbon,and nano iron copper will affect the nickel ions in the Ni-EDTA aqueous solution.The removal rates of EDTA are 20.8%,25.4%,30.3%,and the removal rates of EDTA are 5.4%,7.6%,and 9.6%,respectively.The results show that the removal effect of nano iron carbon and nano iron copper on Ni-EDTA is significantly better than that of nano zero valent iron.The removal effect of iron-based nanomaterials on Ni-EDTA is mainly due to surface chemical adsorption.In addition,the microelectrolysis effect further enhances the removal effect of Ni-EDTA.The combined method of nano iron copper microelectrolysis and Fenton was used to remove complex nickel,and the removal mechanism was analyzed.The initial concentration of nickel is 20 mg/L,the initial p H of the solution is 2.5,the dosage of nanometer iron and copper is 400 mg/L,and the dosage of H₂O₂ is 20 m M.Precipitation is carried out under the conditions,the removal rate of nickel ions in Ni-EDTA solution is 99.8%,and the removal rate of EDTA is 99.3%.The results show that this method can not only remove nickel ions,but also degrade the organic ligand EDTA.Detection and analysis show that the nano iron copper undergoes a micro-electrolysis reaction in the Ni-EDTA solution,and the produced Fe²⁺is oxidized in the air,and the produced Fe³⁺can replace the nickel ions in Ni-EDTA.In addition,Fe²⁺and H₂O₂ undergo a Fenton reaction,and the generated?OH degrades the organic ligand EDTA and releases nickel ions.Under alkaline conditions,nickel ions and Fe³⁺in the solution are removed by co-precipitation.The electroplating wastewater is treated by the nano iron copper microelectrolysis-Fenton combined method.The electroplating wastewater was treated under the conditions of nickel concentration of 1.26 mg/L,initial p H of 2.5,nanometer iron and copper dosage of 80 mg/L,H₂O₂ dosage of 6 m M,and precipitation p H of 10.0.The results showed that the remaining concentration of nickel was lower than the flame detection limit of atomic absorption spectrometer,and the removal rate of total organic carbon in wastewater was 36.1%.The analysis pointed out that the high concentration of K,Na,Ca and other background ions in the electroplating wastewater has a certain inhibitory effect on the removal of total organic carbon.The nano iron copper microelectrolysis-Fenton combined process can effectively degrade EDTA,promote the removal of heavy metal pollutants,and has broad application prospects in the treatment of complex heavy metal wastewater.