Magnetically Recyclable Activated Carbon Prepared from Brewer’s Spent Grain and Its Chromium (VI) Adsorption Study

Magnetic Activated carbon was prepared from a brewery spent grain (BSG) and magnetite using the sol-gel method. The crystal structure, molecular constituent, morphology, and specific surface area of the prepared magnetic activated carbon (MAC) were analyzed using XRD, FTIR, SEM, and BET techniques. The characterization results revealed the successful preparation of MAC material. The removal efficiency of MAC for Cr (VI) from synthetic wastewater and real wastewater was investigated. The adsorption process was optimized numerically and found that solution pH of 2, initial concentration of 40 mg L-1, an adsorbent dosage of 5 g L-1, and a contact time of 30 min were the optimal conditions for removal of Cr (VI) with 97.5% efficacy. The adsorption studies were consistent with the pseudo-second-order kinetics and with Temkin isotherm models with a high regression coefficient (R2) of 0.995 and 0.996 respectively. Moreover, at the optimum conditions, the MAC adsorbent showed the removal of 318 ± 14 mg/L chemical oxygen demand (COD), and 41.3±7.8 mg L-1 biochemical oxygen demand (BOD) of real wastewater collected from the local tannery industry in Ethiopia. Furthermore, the recycled MAC was used repeatedly and showed comparable removal efficiency for five consecutive cycles. As such, magnetic activated carbon made from BSG was found as an alternative efficient adsorbent in tannery wastewater treatment.