Polyaniline: A New Metal-Free Catalyst for Peroxymonosulfate Activation with Highly Efficient and Durable Removal of Organic Pollutants

Abstract

Metal-free heterogeneous catalysts are receiving more and more attention for wastewater remediation by activating peroxymonosulfate (PMS) due to their environmental benign. However, carbon-based materials as the most typical metal-free heterogeneous always suffer from poor durability. Inspired by the fact that a conjugated system may facilitate the electron transfer during PMS activation, we innovatively select polyaniline (PANI) as a new PMS activator and investigate its catalytic performance in detail. It is found that PANI can display better catalytic performance than traditional metal-based catalysts and popular N-doped carbocatalysts in methyl orange (MO) degradation. More importantly, PANI is not only universal for various pollutants degradation but also maintains its catalytic performance in repeated degradation experiments. The stable N sites in the conjugated chains and the oxidation-resistance benzene rings as the building units are considered to be responsible for such an excellent durability. In addition, the influences of some routine factors and actual water backgrounds are comprehensively checked and analyzed. The quenching experiments and electron paramagnetic resonance confirm that MO degradation is achieved through both radical and nonradical pathways, where SO4 •– and 1O2 are primary reactive species. The reaction mechanism is also proposed with the assistance of X-ray photoelectron spectroscopy.

New Insights into the Generation of Singlet Oxygen in the Metal-Free Peroxymonosulfate Activation Process: Important Role of Electron-Deficient Carbon Atoms

“…To further validate whether the carbonyl group in NCN-900 is responsible for the generation of 1 O 2 via PMS activation, the detection of 1 O 2 in the NCN-900/PDS system was performed considering that the carbonyl group was proven to be capable of activating PDS to yield 1 O 2 . , Seen from Figure a, no characteristic signals of 1 O 2 are noted in the EPR spectrum of NCN-900/PDS, excluding the role of the carbonyl group in PMS activation over NCN-900 for 1 O 2 formation. In addition, a very recent work demonstrated that the main origin of 1 O 2 in the course of PMS activation by the polyaniline catalyst was the self-decomposition of PMS. However, the aforementioned results in terms of (i) the observably enhanced BPA oxidation and 1 O 2 production in the NCN-900/PMS system in D 2 O as compared with those in H 2 O (see Figure S8) and (ii) the significant inhibition of BPA degradation over NCN-900 by PMS activation in the presence of a rather low concentration of β-carotene (see Figure e) confirm the generation of 1 O 2 in the NCN-900/PMS system originates from PMS activation by NCN-900 instead of PMS self-decomposition.…”

Confinement of CoP Nanoparticles in Nitrogen‐Doped Yolk‐Shell Porous Carbon Polyhedron for Ultrafast Catalytic Oxidation

“…Ethanol (EtOH) with α‐H is an excellent radical scavenger for both •OH ( k = (1.2–2.8) × 10 9 mol −1 s −1 ) and SO 4 •− ( k = (1.6–7.7) × 10 7 mol −1 s −1 ), whereas tert‐butyl alcohol (TBA) without α‐H is only effective for •OH ( k = (3.8–7.6) × 10 8 mol −1 s −1 ) but not for SO 4 •− ( k = (4.0–9.1) × 10 5 mol −1 s −1 ). [ 33 ] As Figure 4f, the addition of TBA weakly inhibited BPA elimination while the introduction of EtOH significantly depressed the removal ratio of BPA in 8 min from 97.65% to 58.99%, which meant that SO 4 •− rather than •OH was the dominant radical responsible for BPA degradation. Moreover, KI was used as another quencher to probe the existence of surface‐bound radicals.…”

“…•− (k = (1.6-7.7) × 10 7 mol −1 s −1 ), whereas tert-butyl alcohol (TBA) without α-H is only effective for •OH (k = (3.8-7.6) × 10 8 mol −1 s −1 ) but not for SO 4 •− (k = (4.0-9.1) × 10 5 mol −1 s −1 ). [33] As Figure 4f, the addition of TBA weakly inhibited BPA elimination while the introduction of EtOH significantly depressed the removal ratio of BPA in 8 min from 97.65% to 58.99%, which meant that Table 1. Comparison of the BPA degradation efficiency by CoP@MOF-2-C with those by previously reported catalysts through PMS activation.…”

Interface-Promoted Direct Oxidation of p-Arsanilic Acid and Removal of Total Arsenic by the Coupling of Peroxymonosulfate and Mn-Fe-Mixed Oxide

“…As shown in Figure 4b, weak triplet signals of TEMP− 1 O 2 with the peak intensity ratio of 1:1:1 were observed in the PMS-alone solution, which is usually attributed to the self-decomposition of PMS. 48 With the addition of the MnFeO nanocubes, however, no substantial increase in the peak intensity was observed, and the peak intensity did not substantially decrease when p-ASA was present. These results indicate that 1 O 2 was also not a dominant ROS for the p-ASA oxidation.…”