Enhanced oxidation and removal of As(Ⅲ) from water using biomass-derived porous carbon-supported nZVI with high iron utilization and fast adsorption

Abstract

Rapid and effective removal of As(III) from aqueous solutions is crucial and difficult due to its highly toxic and mobile properties. In this study, two kinds of carbonaceous supports, biomass-derived porous carbon (BPC) and biochar (BC), were fabricated for nZVI loading, and then served as adsorbent materials for As(III) removal from water. Characterization results indicated that BPC/nZVI showed more uniformly dispersed nZVI particles on the surface compared to BC/nZVI. Adsorption results showed that BPC/nZVI had highest adsorption capacity for As(III) with the fastest adsorption rate compared with BC/nZVI and pure nZVI. The porous structure and stronger electron accepting capacity for BPC enhanced the reactivity of loading nZVI compared to BC/nZVI. Batch experiments revealed that BPC/nZVI had the highest As(III) Langmuir adsorption capacity up to 177.8 mg/g at pH 7.0, and shorter adsorption equilibrium time within 90 min when compared to BC/nZVI and pure nZVI. The adsorption isotherm and adsorption kinetic of As(III) onto BPC/nZVI were described well by Langmuir model and the pesudo-second-order model, respectively. Additionally, BPC/nZVI exhibited excellent removal performance for As(III) in a broad pH and co-existing anions solution, and kept more than 80% As(III) removal rate after the fourth cycle. Our results indicate that oxidation and complexation are the dominant mechanisms and electrostatic interaction exists for As(III) removal by BPC/nZVI. This study indicates that BPC as supporting materials for nZVI loading is a promising strategy for efficient and fast remediation of As(III)-polluted wastewater.