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Treatment of Ni-EDTA containing wastewater by electrochemical degradation using Ti3+ self-doped TiO2 nanotube arrays anode

2021; Elsevier BV; Volume: 278; Linguagem: Inglês

10.1016/j.chemosphere.2021.130465

1879-1298

Fan Zhang, Weilai Wang, Lei Xu, Chengzhi Zhou, Yanglong Sun, Junfeng Niu,

Advanced Photocatalysis Techniques

Ethylene diamine tetraacetic acid (EDTA) could form stable complexes with nickel due to its strong chelation. Ni-EDTA has significant impacts on human health because of its acute toxicity and low biodegradability, thus some appropriate approaches are required for its removal. In this research, a Ti 3+ self-doped TiO 2 nanotube arrays electrode (ECR-TiO 2 NTA) was prepared and employed in electrochemical degradation of Ni-EDTA. The oxygen evolution potential of ECR-TiO 2 NTA was 2.6 V vs. SCE. More than 96% Ni-EDTA and 88% TOC was removed after reaction for 120 min at current density 2 mA cm −2 at pH 4.34. The degradation of Ni-EDTA was mainly through the cleavage of amine group within Ni-EDTA and furthermore decomposed it into small molecular acids and inorganic ions including NH 4 + and NO 3 − . The electro-deposition of nickel ions at cathode was confirmed by XPS and was greatly affected by the pH of solution. The effects of current density, initial Ni-EDTA concentration, initial pH of solution and HCO 3 − concentration on Ni-EDTA degradation were investigated. The results exhibited that the ECR-TiO 2 NTA had excellent efficiencies in electrochemical degradation of Ni-EDTA. The LSV analysis suggested that Ni-EDTA oxidation on ECR-TiO 2 NTA anode and the production of hydroxyl radical (·OH) on the anode played an important role in the removal of Ni-EDTA. • The ECR-TiO 2 NTA anode had excellent efficiencies in electrochemical degradation of Ni-EDTA. • There were two pathways for the degradation of Ni-EDTA: ·OH radicals attack and direct electron transfer. • The de-complexation of Ni-EDTA and the recovery of Ni 2+ ions were simultaneously achieved.