Photocatalytic Regeneration of Activated Carbon by Combining g-C₃N₄ Photocatalyst under Visible Light Irradiation

Abstract

A green technique was investigated to regenerate the spent activated carbon (AC) by combining AC and carbon nitride (g-C3N4) under visible light irradiation in this study. The AC/g-C3N4 composites were synthesized by the simple calcination process and they had in situ photocatalytic regeneration capacity because of their adsorption-photocatalytic performance. The as-prepared composites were characterized by XRD, FT-IR, XPS, Nitrogen adsorption-desorption, TEM, UV–vis DRS and EIS. It was found that the structure of AC was not destroyed and it could be photocatalytic regeneration by adding g-C3N4. Meanwhile, g-C3N4 was fragmented and distributed uniformly due to the existence of AC, which endowed the composites the more reactive sites and facilitated the transfer of photogenerated charges. The adsorption kinetics and adsorption isotherms were conducted to investigate the adsorption property of the composites. The results demonstrated that the pseudo-second-order model and the Freundlich adsorption model were fitted to the composites. The best regeneration efficiency of the AC in the AC/g-C3N4(40%) composite could reach 60%. The mechanism of the photocatalytic regeneration was also proposed and the desorption process was assumed to the main rate limit step. This study demonstrated that the in situ photocatalytic regeneration technology of AC can be achieved by the AC/g-C3N4 composites.