Insights into Heterogeneous Catalysis of Persulfate Activation on Dimensional-Structured Nanocarbons

Abstract

A variety of dimensional-structured nanocarbons were applied for the first time as metal-free catalysts to activate persulfate (PS) for catalytic oxidation of phenolics and dyes as well as their degradation intermediates. Single-walled carbon nanotubes (SWCNTs), reduced graphene oxide (rGO) and mesoporous carbon (CMK-8) demonstrated superior catalytic activities for heterogeneous PS activation, whereas fullerene (C 60 ), nanodiamonds, and graphitic carbon nitride (g-C 3 N 4 ) presented low efficiencies. Moreover, the carbocatalysts presented even better catalytic performances than activated carbon and metal oxides, such as Fe 3 O 4 , CuO, Co 3 O 4 and MnO 2 . The activity of prepared rGO-900 was further competing to the most efficient electron donor of zero-valent iron (ZVI). Both characterization and oxidation results suggested that the catalytic performances of the nanocarbons are determined by the intrinsic atom arrangements of carbon hybridization, pore structure, defective sites, and functional groups (especially the carbonyl groups). Electron paramagnetic resonance (EPR) spectra revealed that carbocatalysts might act as an excellent electron bridge in activation of PS to oxidize adsorbed water directly to generate hydroxyl radicals, distinct from homogeneous and metal-based catalytic activation. This study discovers several efficient nanocarbons for heterogeneous PS activation, and presents new insights into the catalytic activation processes, providing a fascinating strategy to develop metal-free catalysts for green remediation.

Unveiling the active sites of graphene-catalyzed peroxymonosulfate activation

“…Distinctly, graphene-based materials consist of a honeycomb-like carbon framework with a uniformly sp 2 -hybridized structure and abundant free-flowing π electrons with a great mobility. In spite of the chemically inert culture of the intact carbon matrix, the carbocatalysis can stem from various active sites such as surface imperfect units and vacancies, zigzag/armchair edges, substantial heteroatom doping, and functional groups terminated at the flat (001) boundaries, which could be produced during the synthesis and are expected to possess high chemical activities [8,35].…”

Heterogeneous degradation of refractory pollutants by peroxymonosulfate activated by CoOx-doped ordered mesoporous carbon

“…It was worth noticing that the activation of persulfate by various carbonaceous materials, such as activated carbon [18], reduced graphene oxide (rGO) [19][20][21][22][23], carbon nanotubes (CNTs) [24][25][26][27][28], ordered mesoporous carbon (OMC) [29] and nanodiamond [30,31], had attracted much attention because of their environmental-friendly and high efficiency. Due to its high surface area, accessible mesopores and large pore volume, OMC had been applied in many areas such as adsorbents [32], catalysts and supports [33,34], and electrode materials [35].…”

“…Due to its high surface area, accessible mesopores and large pore volume, OMC had been applied in many areas such as adsorbents [32], catalysts and supports [33,34], and electrode materials [35]. Recently, 3D hexagonally-OMC (CMK-3) and cubically-OMC (CMK-8) were reported for PMS activation and their catalytic activity were much higher than CNTs and 2D graphene nanoplate [29,36]. As a good support, the high surface area of OMC could greatly increase the dispersity of cobalt species, and its instinct catalytic activity for PMS activation contribute to the removal of organic pollutants.…”

Electrochemical Advanced Oxidation Processes (EAOP) to degrade per- and polyfluoroalkyl substances (PFASs)

“…As stated previously, to boost the productivity of radicals and inhibit the emission of O 2 , the electrode materials reported in literatures include platinum (Pt) [43], carbon or graphite (C) [44,45], iridium dioxide (IrO 2 ) [46], ruthenium dioxide (RuO 2 ) [47], tin dioxide (SnO 2 ) [48], boron-doped diamond (BDD) [49], lead dioxide (PbO 2 ) [32], Ti 4 O 7 (Ebonex) [39], TiO 2 nanotube array [34] as well [24,36]. Among them, BDD has been reported to be the best for water treatment [49].…”

“…However, these intermediates have not been detected although they are shown in Figure 5(Cycle IV). Further research is needed for the whole process to be better understood, particularly the in-situ monitoring radicals will enrich the information for mechanism understanding, such as using electron paramagnetic resonance (EPR) [44].…”