Synergetic Electrochemical Degradation of Amoxicillin (AMX) with Sustainable Transition Metal Oxides-Anode and Waste-derived Carbon-Cathode System from a Circular Economy Approach

Abstract

This work explores a novel electrochemical approach for the efficient degradation of amoxicillin (AMX), a widely used antibiotic and emerging water pollutant. This is the first time reported a system combines an IrO₂-Ta₂O₅|Ti anode with cathodes modified using activated carbon derived from two types of waste biomass: Phragmites australis (PA) and Spergularia rubra (SR), having in mind the circular economy. This study evaluated the influence of aeration and current density on AMX degradation efficiency. Results showed that the carbon-modified cathodes enhanced the production of hydrogen peroxide (H₂O₂) via the two-electron oxygen reduction reaction, which facilitated the generation of reactive hydroxyl radicals (^•OH), which improve significantly the degradation rate of AMX. Under optimal conditions (aeration and 2.54 mA cm^-2 current density), the system achieved complete AMX degradation within 30 minutes, with substantial reductions in energy consumption (0.1096 and 0.0895 kWh m^-3 order^-1 for PA and SR, respectively, when applying 2.54 mA cm^-2) compared to conventional platinum cathodes (4.9844 kWh m^-3 order^-1 for Pt). Acute toxicity assays conducted with Vibrio fischeri demonstrated a significant reduction in the toxicity (measured as inhibition percentage), with values of 8.49% and 8.79%, respectively (vs 21.88 % of initial sample). These findings highlight the potential of integrating waste-derived carbon materials with transition metal oxide anodes for sustainable water treatment processes, offering a promising alternative to traditional electrochemical systems for the degradation of pharmaceutical contaminants supporting the sustainable development goal number six (SDG 6) focus on clean water and sanitation.