Electrooxidation of simulated wastewater containing pharmaceutical amoxicillin on thermally prepared IrO2/Ti

Abstract

The electrooxidation of amoxicillin (AMX) on the iridium oxide electrode thermally prepared (400°C) has been investigated by cyclic voltammetry and preparative electrolysis. Physical characterization by Scanning Electron Microscopy (SEM) showed that the IrO₂ electrode has a rough surface with pores' presence. In cyclic voltammetry, the oxidation of AMX occurs directly at the anode's surface or via the higher degree oxide of iridium oxide (IrO₃).  It is noted that the oxidation process of AMX can be controlled by diffusion combined with the phenomenon of adsorption. In preparative electrolysis, the effect of several parameters has been investigated. These are the current density, the support medium, the initial pH. The findings obtained show a weak degradation of amoxicillin. The Chemical Oxygen Demand (COD) reduction rate is less than 11% under our experimental conditions, indicating that the IrO2 electrode leads to the parent compound's conversion. Also, the degradation of the organic compound is favored in a very acidic medium.

Furthermore, the effect of inorganic ions such as SO₄^2-, PO₄^3-, NO₃^-, Cl^- was evaluated. Investigations show that these ions' effects are diverse, with COD reduction rates ranging from 2.47%; 2.68%; 7.7%; 16.41%, and 71.65%, respectively, in the absence and the presence of SO₄^2-, PO₄^3-, NO₃^-, Cl^- ions. SO₄^2- have virtually no effect on enhancing the degradation of amoxicillin. PO₄^3- ions provide a slight improvement in amoxicillin degradation. As for nitrate ions, their influence is 2.31 times that of phosphate ions. Chloride ions improve the performance of the electrooxidation of amoxicillin on IrO2 very significantly. The presence of chloride ions makes it possible to go from 2928.35 (absence of inorganic ions) to 33.19 kWh per Kg of COD. This represents an energy gain of over 98%.