l-Ascorbic acid oxygen-induced micro-electronic fields over metal-free polyimide for peroxymonosulfate activation to realize efficient multi-pathway destruction of contaminants†
Abstract
Peroxymonosulfate (PMS) activation in heterogeneous processes for pollutant removal is a promising water treatment technique. However, the existing rate limiting step of the metal-containing system greatly restrains its performance and increases the consumption of PMS and energy. Herein, we describe an efficient, metal-free strategy for solving these problems. In this study, L-ascorbic acid O-doped carbon–nitrogen–oxygen polymer nano-flowers (OVc-CNOP Nfs) were fabricated via a facile thermal polymerization process. The metal-free OVc-CNOP Nfs showed excellent activity and stability in PMS activation for the degradation of various organic pollutants. Even the refractory endocrine interferon bisphenol A can be completely removed in just 1 min. Doping with O induced bidirectional transfer of electrons on aromatic rings through C–O–C bonding [C(π)→O←C(π)], which led to the formation of micro-electronic fields on the catalyst surface. During the reaction, efficient oxidation of organic pollutants by utilizing the charges of pollutants themselves around the electron-poor C(π) areas inhibited undesirable oxidation of PMS and promoted PMS reduction in the electron-rich O areas to generate hydroxyl (˙OH) and sulfate (SO4˙−) radicals. The reduction of dissolved oxygen to O2˙− around the electron-rich O areas also destroyed the pollutants, and this further drove electron donation from the pollutants and accelerated catalytic oxidation. These multi-pathway synergistic processes involving oxidation of the pollutants themselves and attack by free radicals enabled rapid degradation of contaminants.