Combination of granular activated carbon adsorption and electrochemical oxidation processes in methanol medium for benzene removal

Abstract

• Benzene can be mineralized electrochemically from methanol electrolytes. • Better efficiency of the combined GAC/electrolytic process for removal of benzene. • Formation of anisole opens the possibility of electro-refinery as treatment technology. • Adsorption/electrolysis doesn't reach initially expected efficiency but overcomes water electrolysis. One of the impacts caused by the increase in anthropogenic activities, related to the accelerated urbanization and industrialization, is the increase in emissions of volatile organic compounds (VOC). This type of air pollution has become a matter of great concern nowadays, because of its harmfulness to the environment and human health. Adsorption technologies are one of the most promising methods for decontaminating VOCs from the air because they are simple, inexpensive, and energy efficient. On the other hand, electrochemical treatments have been extensively and successfully studied for water treatment. The combination of an adsorption step followed by an electrochemical treatment, with the regeneration of the adsorbent material, can be an interesting alternative, mainly to overcome the limitations of the treatment of diluted solutions. In this work, the removal of benzene from diluted water solutions were evaluated using a combination of three processes: adsorption, desorption with methanol and electrochemical oxidation with boron-doped diamond electrode (BDD) of the high concentrated solution obtained. This technology is suitable for the recovery of the adsorbent material (granular activated carbon), which can be reused after drying. Two possible concurrent ways to remove benzene from methanol solutions by electrochemical oxidation were found: (1) mineralization and (2) conversion to anisole, a solvent of commercial interest used in the cosmetics industry. The performance of electrochemical treatment for benzene removal from methanol solution was not so different than that in water, but the energy consumption was greater. However, the production of high added-value products is a very interesting finding that will advance the development of more sustainable treatment processes.