Electrochemical regeneration of granular activated carbon saturated by p-nitrophenol in BDD anode system

Abstract

Phenolic compounds have been widely used in metallurgy, petroleum, chemicals, textiles, dye printing and pharmaceuticals. These compounds are persistent, non-biodegradable and harmful for human healthy, whose emission should be restricted before their efficient treatment. Electrochemical regeneration of granular activated carbon (GAC) saturated with p-nitrophenol (p-NO2) has been investigated in Boron-doped Diamond (BDD) anode system. The dominated regeneration mechanism was mainly due to the electrostatic repulsion between negative polarized GAC located at cathode and deprotonated p-NO2 ions. Operating parameters including current density, regeneration time, pH value, electrolyte concentration and flow rate have been investigated systematically. Under the optimized experimental conditions, regeneration efficiency of GAC was as high as 81.6%, without significant declination after five-times adsorption-regeneration cycles. During the regeneration process, organic compounds of p-NO2, which was desorbed from GAC and released into electrolyte, was oxidized at BDD anode surface. Therefore, GAC regeneration and p-NO2 degradation were realized simultaneously. Effects of different anode materials on regeneration process was analyzed and BDD showed superior performance compared with PbO2, SnO2 and Pt anodes, which was attributed to different intermediates formed at anode surface. In summary, GAC saturated with p-NO2 can be regenerated efficiently in BDD anode system with p-NO2 removed simultaneously. All these results demonstrated that electrochemical regeneration in BDD anode system has great potential for practical application.