Treatment of benzene contaminated gas streams by combining adsorption and electrochemical oxidation processes

Abstract

In this work, air streams polluted with benzene were treated by a three-step process, which combines adsorption to remove the pollutants, desorption with methanol to regenerate the adsorbent, and electrochemical treatment to regenerate methanol. The improvement in the sustainability of this process was also evaluated by reusing both the adsorbent (granular activated carbon) and methanol used as solvent in the desorption step. Adsorption isotherm models were used to understand the mechanism of adsorption, and data fitted well the Freundlich model (R2 = 0.9875). Fresh methanol used in the desorption step did not affect the adsorption capacity of GAC, but the treated methanol decreased it by about 10% after three cycles and around 40% after the fourth cycle. Electrochemical treatment in methanol medium produced anisole and dimethyl maleate, that are substances of commercial interest that may be used to increase the value of electrochemical treatment, into a new concept of transforming degradative processes, traditionally faced by the electrochemical treatment of wastes, into a novel electro-refinery process. Thus, the sustainability of the technology and the production of value-added substances are very important findings that will help to change the paradigm of the electrochemical treatment process.