Efficient removal of Tetracycline-Cu complexes from water by electrocoagulation technology

Abstract

Tetracycline (TC) and Cu2+ often coexist in water process and can form TC-Cu complexes. How to effectively remove them from water is becoming an exasperating problem. In current work, electrocoagulation (EC) via bipolar connection was developed to eliminate TC-Cu complexes from water and Fe anode was found to outperform Al anode. Characterization techniques such as XRD, FTIR, UV–vis spectra and UPLC-MS/MS analyses were carried out to explore possible mechanisms using Fe EC. The impacts of main factors including current density, conductivity and TC/Cu molar ratio (2:1, 1:1 and 1:2) were investigated. Results show that as for the three systems with different TC/Cu molar ratios, when the initial pH was 4.3, current density of 4.17 A/m2, conductivity of 1000 μS/cm, the removal of TC, TOC and Cu2+ all reached the maximum after the reaction of 15 min, which was separately 100%, 80.2% and 88.1%, implying excellent mineralization of organic contaminants. EC process displayed high electrodegradation efficiency towards TC-Cu complexes. Appropriate amount of Cu2+ could promote the TC degradation via its catalysis. TC and Cu2+ could be removed via adsorption, hydrogen bond association and coprecipitation by freshly-formed metal hydroxides (green rust, γ-FeOOH and Cu(OH)2). Electroreduction and flotation during EC process could also contribute to the partial removal of Cu2+. The operation cost under the optimum conditions was estimated as 0.050 USD/m3 of treated water. Current study indicates that Fe electrocoagulation was a promising technology for the removal of TC-Cu complexes in water and wastewater treatment.