Influence of anode material and chlorides in the new-gen solid polymer electrolyte cell for electrochemical oxidation - Optimization of Chloroxylenol degradation with response surface methodology

In this study the solid polymer electrolyte - based (SPE-based) system recently developed for electrochemical wastewater treatment is used for the degradation of Chloroxylenol (CXL). To the best of authors knowledge, this is the first study that deals the investigation of the effect of anode material in such electrochemical cell configuration. The most used BDD/SPE cell is compared with DSA/SPE (Ti/RuO2 anode) system considering the effect of chlorides concentration to activate the process mediated by active chlorine. The preliminary tests to evaluate the feasibility of the process show that BDD/SPE is able to completely degrade the CXL reaching a COD removal close to 90 % also in absence of supporting electrolyte and in a low conductive solution (0.025 mS cm(-1)). The DSA anode suffers the lack of chlorides in solution but became more competitive when NaCl is added, with a maximum COD removal equal to 71.6 % with 50 mM NaCl. The response surface methodology based on three-factors Doehlert matrix is applied to optimize the operating conditions for both systems. The selected factors are the current density (2-20 mA cm(-2)), the NaCl concentration (0-20 mM), and CXL concentration (10-100 mg L-1). The optimization analysis allows identifying the operating conditions needed to maximize COD removal and to minimize energy consumptions for BDD/SPE and DSA/SPE setups. In particular, the RSM analysis shows that under peculiar conditions (i = 15.5 mA cm(-2); NaCl > 13 mM) DSA/SPE can reach a COD removal analogous to those obtained with BDD electrode over 90%, suggesting the possibility to exploit this electrode material in solid polymer electrolyte electrochemical cells.