The Electro-Fenton Process for Caffeine Removal from Water and Granular Activated Carbon Regeneration

Abstract

The electro-Fenton process (EF) has faced major challenges, including mass transfer limitations. When the targeted pollutants are present in water at very low concentrations, the degradation kinetics are slower than desired, which leads to high energy consumption. To overcome this drawback, coupled adsorption on activated carbon (AC) and the EF process can be performed. Therefore, the compounds can be preconcentrated on AC before elimination by the EF process. As such, in this study, batch experiments were conducted using low-cost granular activated carbon (GAC) packed in a stainless-steel mesh for the adsorption of caffeine. Once saturated, GAC is used as a cathode during the EF process, where the adsorption capacity is regenerated. This approach allows the regeneration of the AC for multiple cycles and the degradation of the desorbed compounds. The EF process was studied to this end, for the purposes of the removal of caffeine as a model compound. The main goals of this work are (i) to study the removal of caffeine from water in three different matrices and (ii) to regenerate GAC by using the EF process. The results reported in this study show that it is possible to achieve caffeine degradation up to 95%, 100%, and 100%, and a mineralization up to 70%, 72%, and 76% in pure water, simulated wastewater, and wastewater effluent, respectively. In the regeneration process, total elimination of the desorbed caffeine was achieved, and a regeneration efficiency of 50% was obtained for the first cycle. The results confirm the ability of the EF process to achieve regeneration of AC loaded with caffeine.