A unique Si-doped carbon nanocatalyst for peroxymonosulfate (PMS) activation: insights into the singlet oxygen generation mechanism and the abnormal salt effect. Issue 10 (8th September 2020)

• Record Type: Journal Article
• Authors: Duan, Weijian; He, Jinglei; Wei, Ziliang; Dai, Zongren; Feng, Chunhua
• Is Part Of: Environmental science. Volume 7:Issue 10(2020)
• Page Start: 2982
• Page End: 2994
• Publication Date: 2020-09-08
• Subjects: Environmental sciences -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/d0en00848f
• Languages: English
• ISSNs: 2051-8153

Abstract

Abstract : The Si-engaged, carbon-activated peroxymonosulfate (PMS) system proceeding via the non-radical oxidation pathway involving singlet oxygen ( 1 O2 ) represents a promising advanced oxidation process. Abstract : The heteroatom-doped, carbon-activated peroxymonosulfate (PMS) system proceeding via the non-radical oxidation pathway involving singlet oxygen ( 1 O2 ) represents a promising advanced oxidation process (AOP) due to the resistance of 1 O2 to background anions in solution. However, the performance level of pollutant removal is not yet satisfied, and the mechanism of 1 O2 generation remains elusive. Herein, we report the development for the first time of a unique Si-engaged heteroatom ( i.e., N)-doped carbon (Si/N–C) nanomaterial for PMS activation, which exhibits outstanding performance in the removal of various kinds of pollutants and an appreciably wide working pH range of 2.5 to 11. Taking rhodamine B (RhB) as an example, the Si/N–C@PMS system achieved a much higher reaction rate (0.64 min −1 ) than the Si–C (0.047 min −1 ), N–C (0.017 min −1 ), SiO2 (0.021 min −1 ), and Co3 O4 (0.026 min −1 ; a standard catalyst) systems. In addition, the results of electron spin resonance (ESR) and scavenging experiments solidly support the conclusion that the mechanism of 1 O2 generation in this system is via the recombination of superoxide radicals O2 ˙ −, a pathway seldom reported for metal-free, catalyst-activated PMS systems. More importantly, we observed apparent inhibition effects of the anions ( e.g., HCO3 −, HPO4 2−, and PO4 3− ) on the degradation performance, inconsistent with many previous reports suggesting that the 1 O2 -mediated oxidative system possesses a high selectivity toward pollutant degradation in the presence of these anions. Further studies with the anions, including Cl −, HCO3 −, and H x PO4 (3− x ) ( x = 0, 1, 2), suggest that the reaction between O2 ˙ − and these anions is the main reason for the abnormal salt effect. This work will deepen the understanding of 1 O2 formation via the intermediate of O2 ˙ − and provide a new insight into its salt resistance capacity.