Ultrafast Removal of Cr(Vi) By Chitosan Coated Biochar-Supported Nano Zero-Valent Iron Aerogel From Aqueous Solution: Application Performance And Reaction Mechanism

Abstract

Chitosan coated biochar-supported nano zero-valent iron aerogel (C-nZVI@BC) was successfully synthesized for the efficient removal of Cr(VI) from aqueous solution. Results showed that the C-nZVI@BC has a 2.1-fold higher adsorption capacity of Cr(VI) than the uncoated sample. Ultrafast adsorption of Cr(VI) with 61%, 77%, and 87% of the maximum adsorption capacities were achieved within 1 min with the initial concentration of Cr(VI) at 100 mg/L, 300 mg/L, and 600 mg/L, respectively. The C-nZVI@BC exhibited high adsorption performance under aerobic conditions, and showed high Cr(VI) removal rates of >83% in a wide pH range (2–8). The Cr(VI) removal by C-nZVI@BC was fitted well with the pseudo-second-order kinetic and Freundlich models. The key mechanisms for Cr(VI) removal were adsorption, reduction, and complexation. The removal of total Cr was achieved owing to the adsorption/complexation of Cr(III) by the C-nZVI@BC. The batch and column adsorption experiments implied the application potential of C-nZVI@BC for Cr(VI) removal in groundwater. In addition, C-nZVI@BC could be a direct reducing agent for Cr(VI) and an activator of persulfate (PS) for the degradation of antibiotics, and C-nZVI@BC+PS showed 77% and 82% removal of tetracycline and chlortetracycline within 5 min. Overall, C-nZVI@BC was a suitable adsorbent for pollutants removal.

Keywords: Biochar, nZVI, Chitosan, Adsorption, Cr(VI)