Efficient phenol removal by δ-MnO₂ synthesized in situ on a self-supporting membrane

Manganese oxides are effective environmental coupling oxidants for the conversion of phenol; however, previous research has mainly focused on their powdered rather than immobilized forms. To address this gap, the oxidative removal of phenol from aqueous solutions was investigated using δ-MnO₂, which was synthesized in situ and immobilized on a tailorable self-supporting membrane carrier (MnO₂/M). The Freundlich isotherm provided the best fit for adsorption, whereas Sips successfully indicated the highest adsorption capacity. Kinetic analyses showed that the pseudo-second-order and electron transfer control models represented the reaction dynamics, with intra-particle diffusion and liquid film diffusion playing crucial roles. Physicochemical calculations confirmed the exothermic and spontaneous nature of the reaction (ΔG = -31.65 kJ/mol; 298 K). This research also clarifies and elucidates the two-electron direct oxidative transfer processes involved in the oxidative transformation of phenol by the MnO₂/H⁺ heterogeneous system, establishing a framework for advancing environmental remediation using Mn-based materials.