OICC Press International Journal of Recycling of Organic Waste in Agriculture 2251-7715 13 5 2024 06 14 Enhanced removal of Pb2+ from aqueous solutions by iron/manganese binary oxide loaded on Eichhornia crassipes stem biochar 10.57647/ijrowa-y6fq-m572 EN Nguyen Xuan Loc Department of Environmental Science, College of the Environment and Natural Resources, Can Tho University, Can Tho 900000, Vietnam 0000-0003-0423-6179 Tran Tan Bao Department of Environmental Engineering, College of the Environment and Natural Resources, Can Tho University, Can Tho 900000, Vietnam 0009-0002-7891-7866 Phan Thi Thanh Tuyen Department of Environmental Science, College of the Environment and Natural Resources, Can Tho University, Can Tho 900000, Vietnam 0009-0009-2682-4730 Lang Hiep Phong Department of Environmental Engineering, College of the Environment and Natural Resources, Can Tho University, Can Tho 900000, Vietnam 0009-0005-6243-8272 Do Thi My Phuong Department of Environmental Engineering, College of the Environment and Natural Resources, Can Tho University, Can Tho 900000, Vietnam 0009-0000-5777-8751 Journal Article 2024 06 14 Purpose: Biochar modified with metal oxides has proved high capacities in removing heavy metals in wastewater. There is a limited number of studies exploring the potential of Fe-Mn binary oxides-biochar adsorbents for several heavy metals removal from contaminated water; however, the adsorption behavior and mechanism for Pb2+ ions adsorbed on Fe-Mn binary oxide/ Eichhornia crassipes stem biochar composite remains unclear. Method: In this study, Eichhornia crassipes stem biochar (BC) was synthesized and loaded with iron/manganese binary oxide (Fe-Mn@BC) using iron sulfate and potassium permanganate. Results: The successful coating of Fe-Mn oxide particles on the BC surface was confirmed through EDX and FT-IR spectra. Fe-Mn@BC exhibited a specific surface area 4.34 times higher than that of BC (SFe-Mn@BC = 69.636 m2/g; SBC = 16.03 m²/g), resulting in a maximum adsorption capacity for Pb2+ of 1164.95 mg/g, surpassing BC's capacity of 828.84 mg/g. The optimal conditions for Pb2+ removal by Fe-Mn@BC were an initial Pb2+ concentration of 50 mg/L, an adsorbent amount of 0.01 g, an adsorption time of 60 minutes, and an adsorption temperature of 313 K. The adsorption behavior of Pb2+ on Fe-Mn@BC was well-described by the pseudo second-order kinetic and Freundlich models. This process involved a heterogeneous multilayer mechanism that was both spontaneous and endothermic. The adsorption mechanism comprised intra-particle diffusion and chemisorption interactions, including co-precipitation, complexation, ion exchange, and hydrogen bonding. Conclusion: Eichhornia crassipes stem biochar enhanced with iron/manganese binary oxide can efficiently remove Pb2+ from wastewater. Research Highlights The combination of Eichhornia crassipes stem biochar with iron/manganese binary oxide has been proposed as a viable solution, capitalizing on the respective strengths of both materials. The specific surface area of Fe-Mn@BC increased by 4.34 folds. The maximum adsorption capacity of Fe-Mn@BC for Pb2+ was 1164.95 mg/g, surpassing BC's capacity of 828.84 mg/g The adsorption of Pb2+ on Fe-Mn@BC followed a heterogeneous multilayer process, characterized by spontaneity and endothermicity. The iron/manganese binary oxide loaded on Eichhornia crassipes stem biochar demonstrated a higher Pb2+ adsorption capacity compared to its pristine biochar.