Simultaneous electrochemical degradation of tetracycline and metronidazole through a high-efficiency and low-energy-consumption advanced oxidation process

Luyao Wang ^{a, 1}, Yue Liu ^{a, 1}, Di Pang ^a, Haiou Song ^b, Shupeng Zhang ^a, *

Abstract

With the increasing complexity of water environment pollution, it is becoming ever more practical to study the simultaneous removal of multiple pollutants in water. Electrochemical advanced oxidation technology is considered to be one of the most promising green approaches for the degradation of organic pollutants. Herein, Ti³⁺ and oxygen vacancies (V_O) self-doped TiO_2-x nanotube array electrodes are employed to investigate the simultaneous degradation and an energy consumption assessment for the effective removal of the antibiotics tetracycline (TC) and metronidazole (MNZ). The electrocatalytic performance of the nanotube arrays prepared at different reduction times is significantly different. The electrochemical reduction of TiO₂ nanotube arrays for 10 min presents the best degradation performance for TC and MNZ. When a mixed solution of TC and MNZ is simultaneously degraded, the removal rate of TC (50 mg L^-1) and MNZ (50 mg L^-1) within 3 h reaches 100%, while the chemical oxygen demand (COD) removal rate is 79.1%. The energy consumption is significantly reduced compared to the degradation of a single substance. Simultaneously, the current utilization rate of the electrochemical degradation system is also significantly improved, with a specific energy consumption of only 85.78 kWh kg^-1 and an average current efficiency that can reach 20.2%. 

  This conclusion shows that although the service life of hydroxyl radical is very short, if the two pollutants are degraded simultaneously, it will not affect the degradation rate, but can greatly save energy consumption and improve current utilization efficiency. This is of great significance for guiding industrial practice. In practical work, the two polluted water systems can be mixed first and then degraded by electrochemical oxidation, which will not affect the effect, but also greatly save energy consumption.