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.