Electrochemical-driven carbocatalysis as highly efficient advanced oxidation processes for simultaneous removal of humic acid and Cr(VI)

Abstract Electrochemical advanced oxidation processes (AOPs) represent an efficient and promising strategy for dealing with the ever-growing water pollution. Meanwhile, carbocatalysis has long and widely been applied in the fields of synthesis and catalysis because of high activity and selectivity. In this work, we combined the advantages of these two methods and for the first time proposed a conceptual new, novel and promising approach of electrochemical-driven carbocatalysis as highly efficient AOPs for water remediation, which was simply performed by adding carbon-based particles into the electrochemical system. This method shows great potentials for the simultaneous removal of both humic acid (HAC) and Cr(VI) in water, in which HAC was effectively mineralized with a TOC removal efficiency as high as 90% and Cr(VI) was completely removed with a total Cr removal beyond 90%. The presence of carbon particulate materials and their physicochemical properties were first indicated to play critical roles in the developed electrochemical AOPs. These added carbonaceous particles such as activated carbon (AC) and a series of modified AC materials, on one side exerted an important carbocatalytic function with typical AOPs features and on another side, they behaved like numerous galvanic cells with quasi-homogeneous catalytic properties, greatly facilitating mass and electron transfers in the electrochemical system and resulting in a synergistic effect for the removal of combined pollutants. The physicochemical properties of these carbon particulate catalysts facilitated the simultaneous occurrence of adsorption and carbocatalysis, where a synergistic effect between adsorption and catalytic oxidation was confirmed in this electrochemical-driven carbocatalysis system. Moreover, the catalytic performances and mechanisms of this system were found to be dependent on the carbon structures (e.g., surface area, functional groups and hybridization structure, etc.). Very importantly, the energy-effective feature and the carbon materials stability showed a promising prospect of this approach with energy consumption much lower than the ever-reported electrochemical AOPs. This work details the first insight into electrochemical-driven carbocatalysis and provides a new, green and promising approach for effective water remediation, as well as gives new evidence for the synergistic effect between adsorption and catalytic oxidation.