Removal of aqueous Cr(VI) using magnetic-gelatin supported on Brassica-straw biochar

A chemical-modified biochar material (MGBC) derived from Brassica straw was synthesized using magnetic-gelatin as a modification reagent and employed to remove Cr(VI) from aqueous solution. MGBC before and after reacted with Cr(VI) was characterized by FT-IR, XRD, SEM-EDS, XPS, and VSM (Vibrating Sample Magnetometer). Characterization results indicated that the underlying mechanisms of remove Cr(VI) by MGBC were primarily relied on the chelation of functional groups and reduction-coupled surface precipitation. Additionally, the effect of pH, initial Cr(VI) concentration, adsorption time, ionic strength, and coexisting ions on adsorption capacity of MGBC were evaluated and optimized by batch adsorption experiments. All findings illustrated that the maximum adsorption capacity of MGBC for Cr(VI) was 434.85 mg/g obtained at pH = 1 and the adsorption process was highly dependent on pH, and well consistent with Freundlich model and Pseudo-second-order (PSO) model. Furthermore, approximately 72% of equilibrium adsorption capacity for Cr(VI) was still possessed by MGBC under a considerable degree of ionic strength or a given concentration of coexisting ions, which demonstrated that MGBC equipped with strong selective adsorption ability and anti-jamming capability in practical wastewater. All results herein manifested that MGBC equipped with favorable practicability and reusability, which could serve as a low-cost and high-efficiency adsorbent to remove Cr(VI) from complex water environment.