Removal of aqueous Cr(VI) by magnetic biochar derived from bagasse

We prepared a novel adsorbent functionalized by bagasse magnetic biochar (BMBC). To study the removal behaviors and mechanisms of Cr(VI) by BMBC, batch adsorption experiments were conducted by modifying variables, such as pH, adsorption time, BMBC dosages, initial Cr concentration, co-existing ions, and ionic strength, and characterizing BMBC before and after Cr(VI) adsorption. BMBC was primarily composed of Fe₂O₃ and Fe₃O₄ on bagasse boichar with an amorphous structure. The specific surface area of BMBC was 81.94 m² g^-1, and the pH_pzc of BMBC was 6.2. The fabricated BMBC showed high adsorption performance of Cr(VI) in aqueous solution. The maximum Cr(VI) adsorption capacity of BMBC was 29.08 mg g^-1 at 25 ºC, which was much higher than that of conventional biochar sorbents. The adsorption process followed pseudo-second-order kinetics and could be explained by the involvement of the Langmuir isotherm in monolayer adsorption. The crystalline structure of Fe₃O₄ in the BMBC changed slightly during the adsorption process; Fe₃O₄ improved the adsorption of Cr(VI) on BMB. The desorption capacity of Cr(VI) was 8.21 mg g^-1 when 0.2 mol L^-1 NaOH was used as the desorption solution. After being reused three times, the removal efficiency is still as high as 80.36%.