Novel ball-milled biochar-vermiculite nanocomposites effectively adsorb aqueous As(Ⅴ)

Abstract

Ball milling was used to fabricate a nanocomposite of 20% hickory biochar (600 °C) and 80% expanded vermiculite (20%-BC/VE). This novel composite adsorbent had much higher removal of As(V) from aqueous solutions than ball-milled biochar and expanded vermiculite. Characterization of these adsorbents showed that the enhanced As(V) adsorption was ascribed to much larger surface area and pore volume (2–6 times), notable changes in crystallinity, activation of cations, and increased functional groups in the nanocomposite compared with the ball-milled products of their pristine counterparts. The As(V) adsorption process by the 20%-BC/VE fitted well with the pseudo-second-order kinetic model (R2= 0.990) and Langmuir isotherm model (R2= 0.989) with a maximum adsorption capacity of 20.1 mg g−1. The 20%-BC/VE best performed at pH about 6. The adsorption efficiency was not sensitive to the competition of NO3−, Cl−, SO42−, as well as the coexistence of humic acid. However, the adsorption capacity for As(V) was significantly reduced by coexisting with PO43−. The 20%-BC/VE composite can potentially serve as a superior low-cost adsorbent for As(V) removal in real-world applications.