Coupling electro-Fenton process to a biological treatment, a new methodology for the removal of ionic liquids?

Abstract This work proposes a hybrid system for the remediation of toxic and/or refractory pollutants, such as the ionic liquid 1-butyl-1-methylpyrrolidinium chloride, which cannot be degraded by conventional methods such as biological oxidation. Therefore, the electro-Fenton process was evaluated as a pre-treatment stage, since it is a powerful technology capable of degrading complex organic pollutants. First, the key operating parameters (anodic material, iron dosage, current applied and initial pollutant concentration) were evaluated to reach complete ionic liquid degradation (98% total organic carbon abatement). The electro-Fenton treatment target pollutant was accompanied by an increase of its biodegradability, tested from average oxidation state and carbon oxidation state parameters. Based on these values, 30 min of pre-treatment by electron-Fenton process was selected and then the solution thus treated was subjected to biological treatment using bacteria and fungi consortiums. The evolution of TOC and carboxylic acids were followed during assays, attaining an overall abatement of 78% and 67% for bacteria and fungi cultures, respectively. Conversely, a control test of ionic liquid performed without pre-treatment was showed no variation in TOC and no formation of carboxylic acids. Therefore, the feasibility at laboratory scale of the coupling between electro-Fenton and biological treatment has been demonstrated.