Removal of VOCs using electro-Fenton assisted absorption process

Abstract

In this work, the electrochemical oxidation of gaseous streams polluted with three different volatile organic compounds (benzene, toluene, and p-xylene, known as BTX) was evaluated using a jet mixer and electrochemical cell device. Efficiency reached by this technology in the production of hydrogen peroxide was 14% at atmospheric pressure and 12 °C. Results demonstrate the suitability of electrochemically assisted absorption for the treatment of this polluted streams. In the electrolytic assisted absorption (ELAA), keeping a ratio gas flowrate / current intensity of 20 L h−1 A−1, removal efficiencies of 3.14, 1.59, and 0.88 mmol A−1 h−1 were attained for benzene, toluene, and p-xylene, respectively. These values increased up to 12.00, 3.26 and 1.15 mmol A−1 h−1, respectively, when Fe (2+) salt was added to the electrolyte solution to promote the formation of the Fenton reagent, pointing out the higher efficiencies reached by the electro-Fenton assisted absorption (EFAA). The transient response of the systems lasted after four hours of operation and the concentration of pollutants absorbed in the electrolyte decreased in the sequence benzene > toluene > p-xylene (because of their solubility in aqueous solutions) and in the sequence of processes physical absorption (PA) > electrolytic assisted absorption (ELAA) > electro-Fenton assisted absorption (EFAA) (because of the reactivity). Only very low concentrations of carboxylic acids (oxalic and malonic) were accumulated in the absorbent during the process, pointing out that mineralization of these VOCs was the primary reaction pathway.