Iron and manganese removal from borehole water using carbonised orange peels as a biosorbent

Ethical reference #:2021FEBEREC-STD-102

This research reports on the use of carbonised orange peels (COP) made from raw orange peels (ROP) - an agricultural waste by-product, as a biosorbent for removing iron (Fe) and manganese (Mn) in borehole water. The COP biosorbent was prepared by drying, grinding, and carbonising ROP at 600°C in an Argon atmosphere. Batch experiments evaluated the effects of initial concentration, mass (adsorbent dosage), pH, and contact time, while fix-bed column studies assessed continuous flow adsorption performance. SEM showed that the biosorbent before and after carbonisation possessed spherical and elongated flake-like structures with macropores. EDS pointed to an increase in the presence of Fe and Mn in the carbonized peels post biosorption. FTIR on COP before and after biosorption, showed that the adsorbed Fe and Mn were not chemically bound but physically adsorbed, and BET showed that the ROP and COP had very low surface areas typical of carbonaceous materials with COP showing an increase in surface area post carbonisation of the ROP. The adsorption results showed Fe and Mn removal efficiencies of up to 100% and 75%, respectively even in the binary system where there was simultaneous removal of Fe and Mn. The COP biosorbent successfully treated municipal borehole water, achieving adsorption capacities of 11 mg/g for Fe and 5 mg/g for Mn, while reducing the concentration of Fe and Mn from 91 mg/L to 0.05 mg/L and 7 mg/L to 2 mg/L, respectively. The optimal adsorption was at pH 4 and 0.3 g for COP biosorbent mass. Adsorption followed the Langmuir isotherm and pseudo-second-order kinetics, while column data fitted the Yoon-Nelson model more than it did the Bohart-Adams and Thomas models. Prior to treatment, the borehole water appeared orange, likely due to the high Fe and Mn concentrations imparting its distinct colour. After treatment, the water became clear, indicating the effective removal of impurities. This study demonstrates that the use of COP as an adsorbent obtained from ROP biowaste is a sustainable, eco-friendly and effective solution for the simultaneous removal of Fe and Mn heavy metals from Fe and Mn-rich real-world water samples.We report the use of carbonised orange peels (COP) made from raw orange peels (ROP) - an agricultural waste by-product, as a biosorbent for removing iron (Fe) and manganese (Mn) in borehole water. The COP biosorbent was prepared by drying, grinding, and carbonising ROP at 600°C in an Argon atmosphere. Batch experiments evaluated the effects of initial concentration, mass (adsorbent dosage), pH, and contact time, while fix-bed column studies assessed continuous flow adsorption performance. SEM showed that the biosorbent before and after carbonisation possessed spherical and elongated flake-like structures with macropores. EDS pointed to an increase in the presence of Fe and Mn in the carbonized peels post biosorption. FTIR on COP before and after biosorption, showed that the adsorbed Fe and Mn were not chemically bound but physically adsorbed, and BET showed that the ROP and COP had very low surface areas typical of carbonaceous materials with COP showing an increase in surface area post carbonisation of the ROP. The adsorption results showed Fe and Mn removal efficiencies of up to 100% and 75%, respectively even in the binary system where there was simultaneous removal of Fe and Mn. The COP biosorbent successfully treated municipal borehole water, achieving adsorption capacities of 11 mg/g for Fe and 5 mg/g for Mn, while reducing the concentration of Fe and Mn from 91 mg/L to 0.05 mg/L and 7 mg/L to 2 mg/L, respectively. The optimal adsorption was at pH 4 and 0.3 g for COP biosorbent mass. Adsorption followed the Langmuir isotherm and pseudo-second-order kinetics, while column data fitted the Yoon-Nelson model more than it did the Bohart-Adams and Thomas models. Prior to treatment, the borehole water appeared orange, likely due to the high Fe and Mn concentrations imparting its distinct colour. After treatment, the water became clear, indicating the effective removal of impurities. This study demonstrates that the use of COP as an adsorbent obtained from ROP biowaste is a sustainable, eco-friendly and effective solution for the simultaneous removal of Fe and Mn heavy metals from Fe and Mn-rich real-world water samples.