Electrochemical oxidation of low concentrated tetracycline (TC) in aqueous solution: Operation optimization, degradation mechanisms, and detoxification efficiency

The three-dimensional electrode (3DE) process has attracted much attention due to its high efficiency in treating hard-to-degrade organic pollutants. In this work, an efficient removal of low-concentration tetracycline (TC) from aqueous solution was achieved using a 3DE reactor equipped with IrO2-RuO2-Ti anode and granular activated carbon (GAC). In addition, the reliable response surface model (RSM) indicates that maintaining a current density of 12.5mA/cm2 led to effective TC degradation (≥ 96%) within two hours. After verification, •OH and •O2− were identified as the primary active oxygen species in the 3DE system and the addition of particle electrodes significantly enhanced the system's ability to generate •O2−. Additionally, we proposed the complete degradation pathway for TC in the 3DE system, utilizing LC-MS and DFT calculations. Notably, the 3DE system demonstrates superior detoxification efficiency. Many highly toxic intermediates detoxify into minimal amounts of less toxic substances after degradation and exhibit a growth-promoting ability for mung beans comparable to that of pure water. Meanwhile, the outstanding universality, stability, and cost-effectiveness of 3DE systems also contribute to its extensive application prospects. The study presents an efficient, cost-effective, and viable process scheme for removing low-concentration TC from aqueous solutions.