Comprehensive investigation of hydroquinone adsorption in aqueous solution onto new biochar/hausmannite biocomposite derived from agricultural waste material

In this study, the Mn₃O₄-impregnated palm leaves waste biochar (BC) composite (BC-Mn₃O₄) has been synthesized to efficiently remove hydroquinone (HQ) from aqueous solutions. In the batch uptake study, the impact of process parameters like contact time, solution pH, initial HQ concentration, adsorbent dose, and temperature has been studied. Pseudo-second order (PSO) model best fitted the HQ uptake kinetics, while the Freundlich isotherm model best fitted the isothermal equilibrium data. The BC-Mn₃O₄ composite achieved an adsorption capacity of 109.51 mg g⁻¹ and exhibited regeneration capability up to 4 cycles. The adsorption process of HQ onto the BC-Mn₃O₄ was investigated using Monte Carlo (MC) simulations, and the non-covalent interactions (NCl), adsorption energy, and the geometry of the HQ-BC-Mn₃O₄ surface were discussed. Theoretical calculations were performed to elucidate the interactions between the HQ and the BC-Mn₃O₄ composite surface. A proximity was observed between the predicted results by theoretical calculations and the experimental data. In addition, the adsorption energy (E_ads) was negative, implying the uptake process to be spontaneous. HQ adsorption involves π-π interaction, Hydrogen bonding, and pore-filling. The study will serve as a reference for developing promising adsorbents for wastewater treatment.