Treatment of a Highly Concentrated Industrial Effluent with a Pre-Pilot Electrochemical Reactor – Approach to a Practical Application

Abstract

Electrochemical advanced oxidation processes (EAOPs) rely on the non-selective and strong oxidant •OH to mineralize organic pollutants in contaminated effluents [1]. Among them, electro-Fenton (EF) has proven efficient and robust for the degradation of recalcitrant organic pollutants [2]. However, most of the studies on EF are limited to reactors with volumes below 1 L and synthetic effluents. Aiming at practical applications, a pre-pilot scale EF reactor is disclosed here with the highest working volume (50 L) among all reports to date. The reactor incorporated commercial BDD or DSA anodes, as well as our patented cathodes , made of carbon fibers coated with graphene. A local company provided us with real wastewater, originating from the fabrication of flat sheet membranes, with an initial TOC of 10,000 ppm and containing hexane, n, n-dimethylformamide (DMF), trimesoyl chloride (TMC), m-phenylene diamine (MPD) and isopropyl alcohol. One of the biggest challenges of scaling up the EF system was to maintain the same efficiency (in terms of mineralization and energy consumption) as in smaller scale laboratory setups. Figure 1A shows the main results at different stages of scaling up the process. The initial lab-scale stage consisted of beaker experiments with a mineralization efficiency of 98% in 24 h. The bench-scale stage, conducted in a specially-designed flow-through recirculated reactor, saw a decrease in mineralization efficiency (36.2%) and an increase in energy consumption (38.4 Wh g-1 of TOC ), which laid the foundations to improve the engineering design of the pre-pilot scale reactor, using a flow simulation CAD software (Fig. 1B). As a result, the energy consumption decreased to 12.8 Wh g-1 of TOC in that final setup and the 24-h mineralization yield attained 64.8%. In conclusion, we demonstrated the successful scale-up of EF for treatment of real industrial wastewater with high organic load, with good mineralization and energy consumption efficiencies.