Engineering mesoporous nascent MnO₂ colloids for efficient elimination of emerging organic contaminants

Nascent MnO₂ colloids produced during the permanganate oxidation process is highly oxidative and appealing for eliminating emerging organic contaminants (EOCs). However, the nascent MnO₂ colloids usually shows dense bulked structure, which blocks the availability of active sites and further enhancement of the reactivity. Herein, spherical nascent MnO₂ colloids with mesoporous structure were synthesized via redox reactions between colloidal nanospheres of plant polyphenol (e.g., tannic acid) and permanganate. The mesoporous nascent MnO₂ colloids shows highly exposure of active sites with abundant bulk-Mn(III) on the surface (16.2 mol%), and thus exhibits outstanding oxidation performance toward the oxidation of phenolic contaminants. Complete removal of bis-phenol A (BPA, 10 mg/L) was obtained with 1.0 mM of mesoporous nascent MnO₂ colloids in 40 min at neutral pH. Mechanism study reveals that both Mn(III) and Mn(IV) contribute to the oxidation of BPA. The presence of bulk-Mn(III) on the surface greatly promotes the reactivity of the mesoporous nascent MnO₂ colloids, leading to a high kinetic of 0.12 min⁻¹ during the initial 10 min. The nascent mesoporous MnO₂ colloids exhibits high selectivity toward electron rich phenolic contaminants and good performance in complicated water matrix, revealing a promising potential for further application. This work provides a distinct case for engineering novel structured nascent MnO₂ colloids for efficient elimination of EOCs in water.