Enhanced removal of Pb2+ from aqueous solutions by iron/manganese binary oxide loaded on Eichhornia crassipes stem biochar
Authors
Abstract
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.
