Degradation of leachate and high concentration emerging pollutant tetracycline through electro oxidation

In this work, we constructed a three-dimensional electrochemical system (3D-ECO), which included the cathode and anode electrode plates, as well as the screening of three-dimensional particle electrodes and parameter optimization, for the degradation of landfill leachate (LL) containing elevated levels of tetracycline (TC), and explored its mechanism of action. Firstly, titanium-based ruthenium-iridium (Ti/RuO₂-IrO₂), titanium-based ruthenium-iridium-platinum (Ti/Pt-RuO₂-IrO₂), and titanium-based tin-antimony (Ti/SnO₂-Sb₂O₃) were employed as anodes in the electrocatalytic oxidation system, with titanium and stainless steel plates serving as cathodes, to construct the optimal two-dimensional electrocatalytic oxidation system (2D-ECO) through cross-comparison experiments. Subsequently, using granular activated carbon (GAC), coconut shell biochar (CBC), walnut shell carbon (WBC), and bamboo charcoal (BBC) as particle electrodes, a 3D-ECO system was developed. The influence of various operational parameters on treating TC-containing LL was investigated. The optimal operating parameters obtained from the study was: pH = 5, current density of 30 mA/cm², particle dosage of 7 g/L, particle size ranging from 1.70 to 2.00 mm, and electrode spacing of 4 cm. Under these conditions, the COD removal rate of 3D-ECO within three hours was 90.25 %, the TC removal rate was 72.41 %, and the NH₃-N removal rate was 39.52 %. The removal of TC followed a pseudo-first-order kinetic model. Additionally, degradation mechanisms were elucidated through electron paramagnetic resonance (EPR) spectrometer and Tert-Butanol (TBA) quenching experiments, indicating that the degradation primarily occurred through a non-radical (¹O₂) pathway. This research offers a comprehensive analysis of the simultaneous breakdown of intricate LL matrices and TC, enhancing our comprehension of the degradation processes and underlying mechanisms.