Biosorption of V(V) onto Lantana camara biochar modified by H3PO4: Characteristics, mechanism, and regenerative capacity

Biochar has been widely recognized as an environmentally efficient adsorbent for removing heavy metals. However, considering the weak adsorption performance of the original biochar to the oxygen-containing anion, the adsorption of vanadium by biochar has rarely been investigated. This study proposes that H3PO4 activated biochar made from an invasive plant species growing near mines is a novel material to be investigated for V(V) recovery and reuse. As a noxious, invasive plant, Lantana camara L. (LC) has become widely naturalized around the world. Biochar was prepared from LC by pyrolysis at different conditions (200 degrees C, 350 degrees C, 500 degrees C, and 650 degrees C). The adsorption effect of biochar with and without P pretreatment on V(V) in aqueous solution was compared. The results show that biochar prepared from LC impregnated with H3PO4 (MLBC) had the highest adsorption capacity at 500 degrees C, and the maximal adsorption capacity fitted by Langmuir model was 77.38 mg g(-1), which was considerably higher than that of untreated biochar (LBC, 5.89 mg g(-1)). The adsorption procedure was substantially fitted by the Langmuir isotherm and the pseudo second-order kinetic. Additionally, the interaction of V(V) on MLBC is pH-dependent, and slightly acidic conditions are more favorable for adsorption. The characterization results indicated that electrostatic interaction, complexation reaction, and redox reaction were the primary mechanisms. After three cycles of adsorption, the final maximal adsorption capacity of MLBC remained at 76.03% of that of the virgin sample, demonstrating that MLBC had a recyclable capability to eliminate and restore V(V) from aqueous solutions.