Confining Free Radicals in Close Vicinity to Contaminants Enables Ultrafast Fenton‐like Processes in the Interspacing of MoS₂ Membranes

Abstract

Heterogenous Fenton-like reactions are frequently proposed for treating persistent pollutants through the generation of reactive radicals.D espite great efforts to optimize catalyst activity,their broad application in practical settings has been restricted by the low efficiency of hydrogen peroxideo r persulfate decomposition as well as ultrafast self-quenching of the activated radicals.T heoretical calculations predicted that two-dimensional (2D) metallic 1T phase MoS 2 materials with exposed (001) surfaces and (100) edges should have remarkable affinity towards crucial intermediates in the peroxymonosulfate (PMS) activation process.X -ray photoelectron spectroscopya nd in situ Raman spectroscopyw ere used to show that the exposed metallic Mo sites accelerate the ratelimiting step of electron transfer.Alamellar membrane made from as tack of 2D MoS 2 with tunable interspacing was then designed as the catalyst. The non-linear transport between the MoS 2 nanolayers leads to high water diffusivity so that the short-lived reactive radicals efficiently oxidizec ontaminants.Heterogeneous advanced oxidation processes (AOPs) have been implemented in water purification to successfully degrade organic pollutants through the generation of reactive oxygen species (ROS), which enable the unselective oxidation of awide range of aqueous organic pollutants. [1] As core materials for ROSg eneration, heterogenous activators can overcome the inherent drawback of secondary pollution, which is typically encountered with homogeneous AOPs. [2] However,t he performance of AOPs using heterogenous activators currently suffers from low ROS activation efficiency,which is due to the insufficient exposure of actives sites for ROSg eneration. [3] Additionally,u ltrashort radical lifetimes (10 À6 -10 À9 s) hamper the effective diffusion of ROS to the target organic compounds in solution, resulting in inefficient usage of the as-activated ROS.In principle,t he cleavage of peroxyl bonds in AOPs involving chemical oxidants (peroxymonosulfate (PMS), H 2 O 2 )o ccurs by electron transfer from polyvalent metals (Fe, Mn, or Co). [4] Nevertheless,t he free radical yield is primarily determined by the adsorption ability towards the active ingredients.M olybdenum disulfide (MoS 2 ), al ayered transition-metal dichalcogenide,h as been widely applied in catalysis and energy conversion. [5] In particular,t he strong bonding and the highly effective electron transfer induced by the SÀMoÀSb onds are crucial for its outstanding catalytic performance. [6] Remarkably,t heoretical calculations predicted that the (001) edges and (100) surfaces of 1T phase MoS 2 should exhibit strong adsorption energies (E ads )towards PMS molecules.T hus MoS 2 with abundant active sites (Mo 2+ !Mo 6+ )s hould theoretically be an ideal activator for radical generation. However, the gallery height of bulk MoS 2 is too narrow (ca. 0.298 nm) to admit reactants to the interior surface,w here the abundant active sites are located. [7] Achieving high exposure of the active surfaces and e...

Unprecedented Nonphotomediated Hole (h+) Oxidation System Constructed from Defective Carbon Nanotubes and Superoxides

“…In addition, it is worthwhile to mention that the optimal activity of ROCNT-6, with a k -value of 2.72 μmol/g/s (fitted by a modified kinetic model), is higher than the majority of photo/Fenton-like catalysts recently reported ( Table S2 ) and comparable to that of the single cobalt atom catalyst (3.65 μmol/g/s). 30 , 31 …”

“…The removal of BPA in this system maintained 100% over 10 h at a high average permeance of 2850 L/m 2 /h/bar ( Figure 7 h), which is much superior than the best reported MoS 2 membrane (90% BPA removal in 6 h and permeance of 154 L/m 2 /h/bar). 30 Waste water containing only BPA was also applied, and leakage of BPA after only 30 min could be observed, implying that the adsorption of BPA by CNTs made negligible contribution to the high removal efficiency. Moreover, the membrane could also maintain its excellent catalytic performance in actual water.…”

Hydrophobic-modified metal-hydroxide nanoflocculants enable one-step removal of multi-contaminants for drinking water production

“…In the past decades, much research has been focused on additional treatment methods, including adsorption, membrane separation, and advanced oxidation processes (AOPs), for the effective removal of emerging micro-pollutants ( Alsbaiee et al., 2016 ; Chen et al., 2019 ; Miller et al., 2017 ). Despite their achievements, most of the previous studies have relied on the performance (e.g., greater removal of SS and NOM) of conventional pretreatment methods, thereby creating more complex water treatment processes with a higher cost and land occupation ( Benner et al., 2013 ; Decrey et al., 2020 ; Grandclement et al., 2017 ).…”

“…Nanotechnology has demonstrated considerable potential in various water remediation methods, especially in AOPs, adsorption, and membrane filtration ( Chen et al., 2019 ; Gu et al., 2019 ; Wang et al., 2016 ; Zhang et al., 2019a , 2019b ). However, studies employing nanotechnology in flocculation are relatively few ( Simate et al., 2012 ; Yang et al., 2013 ).…”

Peroxymonosulfate Activation on a Hybrid Material of Conjugated PVC and TiO2 Nanotubes for Enhancing Degradation of Rhodamine B under Visible Light

“…Recently, sulfate radical anion-(SO ⋅− 4 ) induced advanced oxidation reactions that have been successfully used in treating organic pollutants in water [7][8][9]. In comparison with hydroxyl radical ( ⋅ OH), SO ⋅− 4 has a higher reduction potential [10]. Also, SO ⋅− 4 has advantages such as pH independence [11], greater oxidation selectivity of organic pollutants, and longer lifetime during the reaction [12].…”