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

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^-, SO₄^2-, as well as the coexistence of humic acid. However, the adsorption capacity for As(V) was significantly reduced by coexisting with PO₄^3-. The 20%-BC/VE composite can potentially serve as a superior low-cost adsorbent for As(V) removal in real-world applications.