Abstract
Abstract
This study aims to investigate the feasibility of utilizing Al-F hydroxide precipitates generated in Al hydroxide [Al(OH)3] adsorption [Al(OH)3-Fads] and aluminum (Al) coagulation [Al(OH)3-Fcoag] for adsorptive removal of As(III) and As(V). Al(OH)3-Fads, Al(OH)3-Fcoag, and pristine Al(OH)3 were characterized by nitrogen sorption, X-ray photoelectron spectroscopy, and fourier transform infrared spectroscopy (FTIR) before and after arsenic adsorption. The kinetic study indicated that As(III) and As(V) adsorption on these Al-based solid wastes followed the pseudo-second-order model. The calculated adsorption capacity of Al(OH)3-Fads and Al(OH)3-Fcoag for As(III) was 48.0 and 31.0 mg/g, while it was 84.0 and 56.3 mg/g for As(V), respectively. These adsorption capacities were 25–50% lower compared with pristine Al(OH)3. Anion exchange of fluoride by H2AsO4− and HAsO42− dominated in As(V) removal by Al(OH)3-Fads, while formation of an As-O complex played a more important role in As(V) removal by Al(OH)3-Fcoag. The maximum concentration of released fluoride after the adsorption of As(III) and As(V) by Al(OH)3-Fads and Al(OH)3-Fcoag was below the Chinese Class-II industrial discharge standard for fluoride (<20 mg/L). Results from this study indicated that the aluminum hydroxides generated in the fluoride removal process could be reclaimed as an adsorbent for As(III)/As(V) removal from industrial wastewater.
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