Functionalization of <i>Shorea faguetiana</i> biochar using Fe₂O₃ nanoparticles and MXene for rapid removal of methyl blue and lead from both single and binary systems

Abstract

The synthesis of polymeric magnetic composites is a promising strategy for the rapid and efficient treatment of wastewater. Lead and methyl blue are extremely hazardous to living organisms. The sorption of Pb²⁺ and the dye methyl blue (MB) by biochar is an ecologically sustainable method to remediate this type of water pollution. We functionalized <i>Shorea faguetiana</i> biochar with Fe₂O₃ and MXene, resulting in Fe₂O₃/BC/MXene composites with an efficient, rapid, and selective adsorption performance. Based on X-ray photoelectron and Fourier transform infrared spectrometry, we found that the Fe₂O₃/BC/MXene composites had an increased number of surface functional groups (F^-, C[double bond, length as m-dash]O, CN, NH, and OH^-) compared with the original biochar. The batch sorption findings showed that the maximum sorption capacities for Pb²⁺ and MB at 293 K were 882.76 and 758.03 mg g^-1, respectively. The sorption phenomena obeyed a pseudo-second-order (<i>R</i>² = 1) model and the Langmuir isotherm. There was no competition between MB and Pb²⁺ in binary solutions, indicating that MB and Pb²⁺ did not influence each other as a result of their different adsorption mechanisms (electrostatic interaction for Pb²⁺ and hydrogen bonding for MB). This illustrates monolayer sorption on the Fe₂O₃/BC/MXene composite governed by chemical adsorption. Thermodynamic investigations indicated that the sorption process was spontaneous and exothermic at 293-313 K, suggesting that it is feasible for practical applications. Fe₂O₃/BC/MXene can selectively adsorb Pb²⁺ ions and MB from wastewater containing multiple interfering metal ions. The sorption capacities were still high after five reusability experiments. This work provides a novel Fe₂O₃/BC/MXene composite for the rapid and efficient removal of Pb²⁺ and MB.