A flexible electrochemical cell setup for pollutant oxidation in a wide electrical conductivity range and its integration with ultrasound

A flexible electrochemical cell setup is proposed to operate in a wide range of electrical conductivity (10-5 ÷ 10-2 S cm-1) avoiding the change of water matrix composition (e.g., addition of salt as a supporting electrolyte to increase conductivity). The system is based on the employment of a solid polymer electrolyte (Nafion®117) sandwiched between a boron-doped diamond (BDD) anode and a TiRuO2 cathode. Mordant orange-1 (MO1) dye is selected as a model compound due to its presence in several effluents with different features (electrical conductivity, water matrix composition, presence of chloride, sulphate). The results highlight a complete MO1 removal under different conditions (low conductivity or presence of sulphate). A chemical oxygen demand (COD) removal over 85% is obtained both in a low conductive solution (1.1 × 10-5 S cm-1) and with 20 mM of Na2SO4 (10.8 10-2 S cm-1). The presence of chloride hinders the COD removal (max ~60%, NaCl 4 mM). An integration with ultrasound (US) is proposed, focusing on ultrasound management as a function of effluent properties. The US application is optimized, and it is recommended for all the process duration only in the presence of sulphate concentration over 20 mM. Otherwise, it must be limited to the first part (90 min) of the process. The development of such a system can help the diffusion of electrochemical technologies for wastewater treatment also in those industrial sectors, which have a variation of wastewater properties during the year (e.g. seasonal production).