Designing 3D-MoS2 Sponge as Excellent Cocatalysts in Advanced Oxidation Processes for Pollutant Control

3D-MoS₂ can adsorb organic molecules and provide multidimensional electron transport pathways, implying a potential application for environment remediation. Here, we study the degradation of aromatic organics in advanced oxidation processes (AOPs) by a 3D-MoS₂ sponge loaded with MoS₂ nanospheres and graphene oxide (GO). Exposed Mo⁴⁺ active sites on 3D-MoS₂ can significantly improve the concentration and stability of Fe²⁺ in AOPs and keep the Fe³⁺/Fe²⁺ in a stable dynamic cycle, thus effectively promoting the activation of H₂O₂/peroxymonosulfate (PMS). The degradation rate of organic pollutants in the 3D-MoS₂ system is about 50 times higher than without cocatalyst. After a 140 L pilot-scale experiment, it still maintains high efficiency and stable AOPs activity. After 16 days of continuous reaction, the 3D-MoS₂ achieves a degradation rate of 120 mg L⁻¹ antibiotic wastewater up to 97.87 %. The operating cost of treating a ton of wastewater is only US$ 0.33, suggesting huge industrial applications.     

CoFe2O4 with MoS2-xOy Nanosheets as a Co-catalyst for Enhanced Activation of Peroxydisulfate in Advanced Oxidation Processes

The application of advanced oxidation processes (AOPs) based on sulfate radicals for degrading persistent organic pollutants faces challenges due to the inefficient activation of peroxydisulfate (PDS) oxidant. Herein, a composite CoFe₂O₄/MoS_2-xO_y (CFM) catalyst consisting of CoFe₂O₄ nanoparticles uniformly dispersed on the nanosheets of oxygen-incorporated MoS₂ (MoS_2-xO_y) with flower-like morphology are fabricated through a facile two-step hydrothermal method, which results in the enhanced activation of PDS and a highly efficient degradation of phenolic pollutants. The oxygen-doping in MoS_2-xO_y leads to unsaturated sulfur and active sites on the surface of MoS₂ for accelerating the rate limiting step of Fe^III/Fe^II reduction cycle in PDS-CFM reaction. Aiming at the refractory organic pollutants in actual coking wastewater, CFM co-catalyst is introduced into a hydrogel made up of polyvinyl alcohol (PVA) and coal-tar pitch oxides (PO) to construct a multifunctional CFM@PO/PVA hydrogel. Upon hybrid CFM@PO/PVA, the coupling of the enhanced AOP with solar-driven interfacial vapor generation (SIVG) technology contributes to the degradation efficiency, the removal rate of phenol in solution and the total organic carbon in coking wastewater can reach 98 % and 91 %, respectively. The integration of heterogeneous AOPs with SIVG system provides a feasible strategy for the eco-friendly efficient purification of industrial wastewater.     

Sustainable activation of peroxymonosulfate by the Mo(IV) in MoS2 for the remediation of aromatic organic pollutants

Although MoS₂ has been proved to be a very ideal cocatalyst in advanced oxidation process (AOPs), the activation process of peroxymonosulfate (PMS) is still inseparable from metal ions which inevitably brings the risk of secondary pollution and it is not conducive to large-scale industrial application. In this study, the commercial MoS₂, as a durable and efficient catalyst, was used for directly activating PMS to degrade aromatic organic pollutant. The commercial MoS₂/PMS catalytic system demonstrated excellent removal efficiency of phenol and the total organic carbon (TOC) residual rate reach to 25%. The degradation rate was significantly reduced if the used MoS₂ was directly carried out the next cycle experiment without any post-treatment. Interestingly, the commercial MoS₂ after post-treated with H₂O₂ can exhibit good stability and recyclability for cyclic degradation of phenol. Furthermore, the mechanism for the activation of PMS had been investigated by density functional theory (DFT) calculation. The renewable Mo⁴⁺ exposed on the surface of MoS₂ was deduced as the primary active site, which realized the direct activation of PMS and avoided secondary pollution. Taking into account the reaction cost and efficient activity, the development of commercial MoS₂ catalytic system is expected to be applied in industrial wastewater.     

The Photo-Fenton Oxidation — A cheap and efficient wastewater treatment method

Advanced Oxidation Processes (AOPs) for wastewater treatment are gaining more importance since biological treatment plants are often not sufficient for highly contaminated or toxic wastewaters. In order to find out the most efficient and cheap AOP, investigations were concentrated on methods that can use sunlight. The systems TiO₂/UV, Fe²⁺/H₂O₂/UV (Photo-Fenton reaction), Fe²⁺/O₂/UV and Fe²⁺/O₃/UV were compared. Since the Photo-Fenton system was the most effective, pilot plant experiments with industrial wastewaters and sunlight experiments were carried out. Finally a rough cost estimate shows that Photo-Fenton treatment with sunlight is far cheaper than other available AOPs, namely ozonization.     

Study on catalytic mechanisms of Fe3O4-rGOx in three typical advanced oxidation processes for tetracycline hydrochloride degradation

This study explored the catalytic mechanism and performance impacted by the materials ratio of Fe₃O₄-GO_x composites in three typical advanced oxidation processes (AOPs) of O₃, peroxodisulfate (PDS) and photo-Fenton processes for tetracycline hydrochloride (TCH) degradation. The ratio of GO in the Fe₃O₄-GO_x composites exhibited different trends of degradation capacity in each AOPs based on different mechanisms. Fe₃O₄-rGO_20wt% exhibited the optimum catalytic performance which enhanced the ozone decomposition efficiency from 33.48% (ozone alone) to 51.83% with the major reactive oxygen species (ROS) of O₂^??. In PDS and photo-Fenton processes, Fe₃O₄-rGO_5wt% had the highest catalytic performance in PDS and H₂O₂ decomposition for SO₄^??, and ^?OH generation, respectively. Compared with using PDS alone, PDS decomposition rate and TCH degradation rate could be increased by 5.97 and 1.73 times under Fe₃O₄-rGO_5wt% catalysis. In the photo-Fenton system, Fe₃O₄-rGO_5wt% with the best catalyst performance in H₂O₂ decomposition, and TCH degradation rate increased by 2.02 times compared with blank group. Meantime, the catalytic mechanisms in those systems of that the ROS produced by conversion between Fe²⁺/Fe³⁺ were also analyzed.     

Study of the Photodegradation Kinetics and Pathways of Hexaflumuron in Liquid Media

Hexaflumuron, one of the benzoylphenylurea insect growth regulators, can be leached into surface water and thus having a potential impact on aquatic organisms. In this study, the photodegradation processes of hexaflumuron under high‐pressure mercury lamp irradiation were assessed. The photodegradation kinetics were studied, as were the effects of pH, different light sources, organic solvents and environmental substances, including nitrate ions (NO₃^?), nitrite ions (NO₂^?), ferrous ions (Fe²⁺), ferric ions (Fe³⁺), humic acid, sodium dodecyl sulfate (SDS) and hydrogen peroxide (H₂O₂). Three photodegradation products in methanol were identified by gas chromatography‐mass spectrometry (GC‐MS). In general, the degradation of hexaflumuron followed first‐order kinetics. In the four media studied, the photodegradation rate order was n‐hexane > methanol > ultrapure water > acetone. Faster degradation was observed under high‐pressure mercury lamp irradiation than under xenon lamp irradiation. The pH had a considerable effect, with the most rapid degradation occurring at pH 5.0. The photodegradation rate of hexaflumuron was promoted in the presence of NO₃^?, NO₂^?, Fe²⁺, humic acid, SDS and H₂O₂, but inhibited by Fe³⁺. Moreover, the presumed photodegradation pathway was proposed to be the cleavage of the urea linkage.     

Selective Production of CO from Organic Pollutants by Coupling Piezocatalysis and Advanced Oxidation Processes

To date, the chemical conversion of organic pollutants into value-added chemical feedstocks rather than CO₂ remains a major challenge. Herein, we successfully developed a coupled piezocatalytic and advanced oxidation processes (AOPs) system for achieving the conversion of various organic pollutants to CO. The CO product stems from the specific process in which organics are first oxidized to carbonate through peroxymonosulfate (PMS)-based AOPs, and then the as-obtained carbonate is converted into CO by piezoelectric reduction under ultrasonic (US) vibration by using a Co₃S₄/MoS₂ catalyst. Experiments and DFT calculations show that the introduction of Co₃S₄ not only effectively promotes the transfer and utilization of piezoelectric electrons but also realizes highly selective conversion from carbonate to CO. The Co₃S₄/MoS₂/PMS system has achieved selective generation of CO in actual complex wastewater treatment for the first time, indicating its potential practical applicability.     

COD reduction of waste water streams of active pharmaceutical ingredient – Atenolol manufacturing unit by advanced oxidation-Fenton process

Active pharmaceutical intermediates (API) in waste waters have adverse effects on aquatic life and environment. The API have high COD value and low BOD₃ and hence difficult to treat biologically. In this study, advanced oxidation processes (AOPs) utilizing the H₂O₂/Fe⁺², Fenton reactions were investigated in lab-scale experiments for the degradation of Atenolol containing waste water streams. The experimental results showed that the Fenton process using H₂O₂/Fe⁺² was the most effective treatment process. With Fenton processes, COD reduction of wastewater can be achieved successfully. It is suggested that Fenton processes are viable techniques for the degradation of Atenolol from the waste water stream with relatively low toxic by-products in the effluent which can be easily biodegraded in the activated sludge process. Hence, the Fenton process with H₂O₂/Fe⁺² is considered a suitable pretreatment method to degrade the active pharmaceutical molecules and to improve the biodegradability of waste water.     

A Water‐Stable Terbium(III)–Organic Framework as a Chemosensor for Inorganic Ions,Nitro‐Containing Compounds and Antibiotics in Aqueous Solutions

Effective detection of organic/inorganic pollutants, such as antibiotics, nitro‐compounds, excessive Fe³⁺ and MnO₄^?, is crucial for human health and environmental protection. Here, a new terbium(III)–organic framework, namely [Tb(TATAB)(H₂O)]?2H₂O ( Tb‐MOF , H₃TATAB=4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐m‐aminobenzoic acid), was assembled and characterized. The Tb‐MOF exhibits a water‐stable 3D bnn framework. Due to the existence of competitive absorption, Tb‐MOF has a high selectivity for detecting Fe³⁺, MnO₄^?, 4‐nirophenol and nitroimidazole (ronidazole, metronidazole, dimetridazole, ornidazole) in aqueous through luminescent quenching. The results suggest that Tb‐MOF is a simple and reliable reagent with multiple sensor responses in practical applications. To the best of our knowledge, this work represents the first Tb^III‐based MOF as an efficient fluorescent sensor for detecting metal ions, inorganic anions, nitro‐compounds, and antibiotics simultaneously.     

A EuIII‐MOF with Bis(2‐carboxyethyl)isocyanurate for Luminescence Sensing of Fe3+ and SCN– Ions

The water‐stable 3D lanthanide‐organic framework (Ln‐MOF) {[Eu(bci)(H₂O)] · 2H₂O}_n ( 1 ) [H₂bci = bis(2‐carboxyethyl)isocyanurate] was synthesized under hydrothermal conditions. Compound 1 ‐ Eu exhibits a 3D open‐framework connected by Eu–(μ‐O)₂–Eu chains and bci ligands. Meanwhile, 1 ‐ Eu exhibits highly efficient luminescent sensing for environmentally relevant Fe³⁺ and SCN^– ions through luminescence quenching. These results indicated that it could be utilized as a multi‐responsive luminescence sensor.     

Heterogeneous Fenton Degradation of Organic Pollutants in Water Enhanced by Combining Iron-type Layered Double Hydroxide and Sulfate

Water pollution derived from organic pollutants is one of the global environmental problems. The Fenton reaction using Fe²⁺ as a homogeneous catalyst has been known as one of clean methods for oxidative degradation of organic pollutants. Here, a layered double hydroxide (Fe²⁺Al³⁺-LDH) containing Fe²⁺ and Al³⁺ in the structure was used to develop a “heterogeneous” Fenton catalyst capable of mineralizing organic pollutants. We found that sulfate ion (SO₄²⁻) immobilized on the Fe²⁺Al³⁺-LDH significantly facilitated oxidative degradation (mineralization) of phenol as a model compound of water pollutants to carbon dioxide (CO₂) in a heterogeneous Fenton process. The phenol conversion and mineralization efficiency to CO₂ reached >99% and ca. 50%, respectively, even with a reaction time of only 60 min.     

Construction of a 2D Graphene‐Like MoS2/C3N4 Heterojunction with Enhanced Visible‐Light Photocatalytic Activity and Photoelectrochemical Activity

A novel graphene‐like MoS₂/C₃N₄ (GL‐MoS₂/C₃N₄) composite photocatalyst has been synthesized by a facile ethylene glycol (EG)‐assisted solvothermal method. The structure and morphology of this GL‐MoS₂/C₃N₄ photocatalyst have been investigated by a wide range of characterization methods. The results showed that GL‐MoS₂ was uniformly distributed on the surface of GL‐C₃N₄ forming a heterostructure. The obtained composite exhibited strong absorbing ability in the ultraviolet (UV) and visible regions. When irradiated with visible light, the composite photocatalyst showed high activity superior to those of the respective individual components GL‐MoS₂ and GL‐C₃N₄ in the degradation of methyl orange. The enhanced photocatalytic activity of the composite may be attributed to the efficient separation of electron–hole pairs as a result of the matching band potentials between GL‐MoS₂ and GL‐C₃N₄. Furthermore, a photocatalytic mechanism for the composite material has been proposed, and the photocatalytic reaction kinetics has been measured. Moreover, GL‐MoS₂/C₃N₄ could serve as a novel sensor for trace amounts of Cu²⁺ since it exhibited good selectivity for Cu²⁺ detection in water.     

球状MoS2/WO3复合半导体制备及其对RhB的光催化性能

采用水热法成功制备了MoS₂/WO₃复合半导体光催化剂,分别通过SEM、TEM、EDS、XRD、Raman和DRS对催化剂的形貌,组成及结构进行表征,并用BET模型计算比表面积。对比发现球状MoS₂/WO₃对罗丹明B（RhB）的光降解效率明显高于纯WO₃、片状MoS₂/WO₃复合半导体。针对球状MoS₂/WO₃复合半导体,分别研究了MoS₂不同负载量（0.5%,1%,2%,5%,10%）对RhB光催化降解性能的影响,结果表明MoS₂含量为2%时催化效果最佳。同时,研究了溶液的pH值（pH=1,3,6,7,11）对光催化降解反应活性的影响,结果显示pH=6时降解率最高。当催化剂量增加到1 g·L^-1时,30min后RhB降解率达到96.6%。球状MoS₂/WO₃的瞬态光电流为0.050 6 mA·cm^-2,比纯WO₃提高了2.4倍。经过5次循环实验,球状MoS₂/WO₃复合半导体催化剂仍能保持90%的高降解率。     

Photo‐Assisted Immobilized Fenton Degradation up to pH 8 of Azo Dye Orange II Mediated by Fe3+/Nafion/Glass Fibers

Fe³⁺ Ions have been immobilized into very thin Nafion films cast onto a glass‐fiber mat immersed in an alcoholic solution of Nafion oligomers. This immobilized Fenton catalyst was used to abate/mineralize the azo dye Orange II, taken as a model organic compound. The abatement of Orange II on the Fe³⁺/Nafion/glass fibers was observed to proceed within the same time period as when Nafion alone was used to immobilize the Fe³⁺ ions during the photo‐Fenton reaction. The amount of Nafion in the Nafion Fe³⁺/Nafion/glass fibers was ca. 15 times less per unit surface area compared to Fe³⁺‐exchanged on conventional Nafion membranes used to immobilize Fe³⁺ ions. Orange II solutions under visible‐light irradiation in the presence of H₂O₂ were mineralized up to pH 8 with a kinetics comparable to that found during the degradation runs at pH 3. Repetitive mineralization cycles mediated by the Fe³⁺/Nafion/glass fibers under visible light did not show any decrease in the activity of the immobilized catalysts. A reaction mechanism consistent with the experimental data is suggested. The morphology of the Fe³⁺/Nafion/glass fibers was characterized by scanning electron microscopy (SEM) showing thin Nafion films cast deposited on the glass fibers. Transmission‐electron‐microscopy (TEM) micrographs reveal Fe³⁺‐oxy‐hydroxide particles of 3 – 6 nm before and after repetitive Orange II photodegradation. X‐Ray photoelectron spectroscopy (XPS) provided the evidence for the existence of Fe clusters on the topmost layer of the catalyst mainly as Fe^III. The improvements brought by the glass fibers are a) the use of low quantities of expensive Nafion supported on glass mats to achieve dye degradation rates comparable to Nafion alone and b) Fenton‐mediated degradation of azo dyes at pH 8 without the costly initial acidification usually needed for this type of treatment.     

球状MoS_2/WO_3复合半导体制备及其对RhB的光催化性能

采用水热法成功制备了MoS_2/WO3复合半导体光催化剂,分别通过SEM、TEM、EDS、XRD、Raman和DRS对催化剂的形貌,组成及结构进行表征,并用BET模型计算比表面积。对比发现球状MoS_2/WO3对罗丹明B(Rh B)的光降解效率明显高于纯WO3、片状MoS_2/WO3复合半导体。针对球状MoS_2/WO3复合半导体,分别研究了MoS_2不同负载量(0.5%,1%,2%,5%,10%)对Rh B光催化降解性能的影响,结果表明MoS_2含量为2%时催化效果最佳。同时,研究了溶液的p H值(p H=1,3,6,7,11)对光催化降解反应活性的影响,结果显示p H=6时降解率最高。当催化剂量增加到1 g·L-1时,30 min后Rh B降解率达到96.6%。球状MoS_2/WO3的瞬态光电流为0.050 6 m A·cm-2,比纯WO3提高了2.4倍。经过5次循环实验,球状MoS_2/WO3复合半导体催化剂仍能保持90%的高降解率。     

Enhanced Separation of Potassium Ions by Spontaneous K+‐Induced Self‐Assembly of a Novel Metal–Organic Framework and Excess Specific Cation–π Interactions

A novel metal–organic framework (MOF) was fabricated by spontaneous K⁺‐induced supramolecular self‐assembly with the embedded tripodal ligand units. When the 3D ligand was loaded onto Fe₃O₄@mSiO₂ core‐shell nanoparticles, it could effectively separate K⁺ ions from a mixture of Na⁺, K⁺, Mg²⁺, and Ca²⁺ ions through nanoparticle‐assisted MOF crystallization into a Fe₃O₄@mSiO₂@MOF hybrid material. Excess potassium ions could be extracted because of the specific cation–π interaction between K⁺ and the aromatic cavity of the MOF, leading to enhanced separation efficiency and suggesting a new application for MOFs.     

A Bifunctional Luminescent Metal–Organic Framework for the Sensing of Paraquat and Fe3+ Ions in Water

The hydrothermal reaction of Zn²⁺ ions with a mixture of two ligands, Hcptpy and H₃btc (Hcptpy=4‐(4‐carboxyphenyl)‐2,2′:4′,4′′‐terpyridine; H₃btc=1,3,5‐benzenetricarboxylic acid), led to the formation of a 3D metal–organic framework (MOF) with 1D channels, [Zn₂(cptpy)(btc)(H₂O)]_n ( 1 ), which was structurally characterized by using single‐crystal X‐ray diffraction (SXRD). In MOF 1 , two independent Zn²⁺ ions were interconnected by btc^3? ligands to form a 1D chain, whilst adjacent Zn²⁺ ions were alternately bridged by cptpy^? ligands to generate a 2D sheet, which was further linked by 1D chains to form a 3D framework with a new (3,3,4,4)‐connected topology. Furthermore, compound 1 also exhibited excellent stability towards air and water and, more importantly, luminescence experiments indicated that it could serve as a probe for the sensitive detection of paraquat (PAQ) and Fe³⁺ ions in aqueous solution.     

Mussel‐inspired decoration of Ni(OH)2 nanosheets on 2D MoS2 towards enhancing thermal and flame retardancy properties of poly(lactic acid)

In the present work, a facile and environmental method was developed to fabricate the novel functionalized MoS₂ hybrid. Firstly, MoS₂ nanosheets were coated with polydopamine (PDA) through the self‐polymerization of dopamine (MoS₂‐PDA) in a buffer solution. Then the decoration of Ni(OH)₂ on the MoS₂‐PDA was synthesized because of the strong affinity of Ni²⁺ with hydroxyl groups in PDA. Finally, the as‐synthesized MoS₂‐PDA@Ni(OH)₂ was introduced into poly(lactic acid) (PLA) matrix to explore flame retardancy, thermal stability, and crystalline property of the composites. As confirmed by X‐ray diffraction (XRD), Fourier‐transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), the MoS₂ nanosheets were dually modified with PDA and Ni(OH)₂ without destroying the original structures. The thermal degradation of PLA with MoS₂‐PDA@Ni(OH)₂ generated a notably higher yield of char. Moreover, the crystallization rate of composites is higher than neat PLA. The cone calorimeter test revealed that the introduction of 3% MoS₂‐PDA@Ni(OH)₂ resulted in lower Peak Heat Release Rate (PHRR) (decreased by 21.7%). Thus, the research provided an innovative functionalization method for manufacturing PLA composites with high performances.     

Hydrophobic poly(lauryl methacrylate)‐coated magnetic nano‐composite particles for removal of organic pollutants

This paper described a simple novel technique to prepare magnetic nano‐composite particles coated with highly crosslinked poly(lauryl methacrylate) (PLMA), a hydrophobic polymer because of its long chain alkyl group for application in waste water purification. Nano‐sized magnetite (Fe₃O₄) particles prepared by coprecipitation of Fe²⁺ and Fe³⁺ from their alkali aqueous solution were encapsulated with SiO₂ following treatment with tetraethylorthosilicate (TEOS). Finally precipitation copolymerization of LMA and divinyl benzene (DVB) in the presence of Fe₃O₄/SiO₂ particles was carried out within stable isolated droplets containing hexadecane–toluene mixture (4:1 mixture HD‐T). The produced PLMA‐coated magnetic composite particles named as Fe₃O₄/SiO₂/P(LMA‐DVB) were characterized by Fourier Transform IR (FTIR), transmission electron microscopy (TEM), thermogravimetry (TG) and X‐ray diffractometer (XRD) analyses. The performance of the composite particles was evaluated for the removal of organic pollutants from water. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of Complexation on Photocatalytic Degradation of Dissolved Organic Nitrogen Compounds

Abstract

The effect of metal ions on TiO₂ mediated photocatalytic oxidation for the determination of dissolved organic nitrogen compounds is investigated. Ethylenediaminetetraaceticacid was chosen as a model molecule for DON compounds. At pH 2, 5, 7, and 10 aqueous EDTA solutions were irradiated at 254 nm in the presence of Fe²⁺, Cu²⁺, Zn²⁺, Ni²⁺ or Co²⁺ ions. The sum of produced nitrate, nitrite, and ammonium ion concentrations gave the total oxidation recovery. At low pH, the photocatalytic oxidation recoveries of Fe‐EDTA, Ni‐EDTA, and Co‐EDTA were significantly lower than the photocatalytic degradation of EDTA. The presence of free Fe²⁺, Ni²⁺, and Co²⁺ ions decreased the photocatalytic oxidation recovery. The [NH₄ ⁺]/[NO₃ ^?] ratio was higher for Cu‐EDTA.