Solid polymer electrolyte as an alternative approach for the electrochemical removal of herbicide from groundwater

Groundwater represents one of the primary freshwater sources, but their pollution is rapidly increasing, and the development of tailored processes is mandatory. In this scenario, electrochemical advanced oxidation processes (EAOPs) represent a promising alternative to face this issue. Their application to groundwater is limited by low electrical conductivity, which directly affects cell voltage and then operating costs. In this paper, three different approaches to overcome this constrain are compared using a BDD anode and a Ti/RuO2 cathode. The first is the addition of a supporting electrolyte as sodium sulfate (Na2SO4); despite its efficacy to increase conductivity, some new problems are introduced in water source management and treatment plant for the electrolyte removal. An alternative approach is the reduction of gap-electrode from 5 mm up to some microns, equivalent to the thickness of a plastic mesh, used to avoid electrodes short-circuit. The third innovative method proposed here is the substitution of insulated mesh with an ionic conductor layer, a solid polymer electrolyte (SPE), like Nafion®117 sandwiched between the electrodes. This modification allows increasing electrochemical performance such as herbicide and COD removal, preserving energy consumptions. Moreover, SPE does not show any performance deterioration in the first 30 h of utilisation. The results suggest that the usage of SPE can be a promising approach for the treatment of groundwater.