New insight of Mn(III) in δ-MnO for peroxymonosulfate activation reaction: Via direct electron transfer or via free radical reactions.

Due to the increasing of industrial plastic waste and its refractory characteristics, it is extremely urgent to develop new degradation technology and environmentally friendly catalyst for industrial plastic waste. Manganese oxides are one of the most promising candidates for the catalytic degradation of plastic wastes. However, an improved understanding of the structural properties affecting their catalytic activity is required for high-efficient wastewater treatment. We herein report the surface reactivity effects of δ-MnO structural defects with regards to Bisphenol A (BPA) degradation/probe in the presence of peroxymonosulfate (PMS). Four δ-MnO samples with different Mn(III) contents (different Mn(III)-deficient sample) were prepared and their structural properties as well as surface reactivity were characterized by batch test, ESR and XAFS analysis. For the Mn(III)-deficient sample, BPA removal was principally affected by direct electron transfer, with the adsorbed BPA degraded following hydroxylation. In contrast, a small fraction of Mn(III) substitution in δ-MnO could significantly encouraged the activation of PMS to produce SO☐and ☐OH, and a BPA degradation via beta scission. Moreover, the Mn(III)-rich δ-MnO demonstrate a high BPA removal rate even with a low sample load, which performed well following a reuse of five times. Our results provide a new way for the improvement of δ-MnO activity for the use of industrial plastic wastes treatment.