Oxidation of emerging organic contaminants by in-situ H_(2)O_(2) fenton system

The existence and risk of emerging organic contaminants(EOCs)have been under consideration and paid much effort to degrade these pollutants.Fenton system is one of the most widely used technologies to solve this problem.The original Fenton system relies on the hydroxyl radicals produced by Fe(Ⅱ)/H_(2)O_(2) to oxidize the organic contaminants.However,the application of the Fenton system is limited by its low iron cycling efficiency and the high risks of hydrogen peroxide transportation and storage.The introduction of external energy(including light and electricity etc.)can effectively promote the Fe(Ⅲ)/Fe(Ⅱ)cycle and the reduction of oxygen to produce hydrogen peroxide in situ.This review introduces three in-situ Fenton systems,which are electro-Fenton,Photo-Fenton,and chemical reaction.The mechanism,influencing factors,and catalysts of these three in-situ Fenton systems in degrading EOCs are discussed systematically.This review strengthens the understanding of Fenton and in-situ Fenton systems in degradation,offering further insight into the real application of the in-situ Fenton system in the removal of EOCs.

Singlet oxygen synergistic surface-adsorbed hydroxyl radicals for phenol degradation in CoP catalytic photo-Fenton

In recent years,there have been numerous studies on Fenton or Fenton-like reactions mediated by nonfree radicals such as singlet oxygen(1O_(2));however,there are few studies on the synergistic effect of 1O_(2) and free radicals on the degradation of organic molecules,such as phenol in Fenton reaction.In this study,a cocatalyst,CoP,commonly used in photocatalysis was synthesized using a simple two-step method,and a CoP/Fe^(2+)/AM1.5 system was constructed by introducing Fe^(2+)and simulated sunlight(AM1.5)irradiation.The newly constructed CoP/Fe^(2+)/AM1.5 system could effectively degrade various organic pollutants,including dyes,phenols,and antibiotics.Radical quenching experiments and electron paramagnetic resonance detection confirmed that there were three reactive oxygen species(ROS)in the CoP/Fe^(2+)/AM1.5 system,including·OH_(ads),·O_(2)^(-),and 1O_(2).Further,combined with the liquid chromatogram of phenol,its intermediate products,and the fluorescence diagram of o-hydroxybenzoic acid,it can be concluded that a synergistic effect exists between 1O_(2) and the surface-adsorbed·OH_(ads) in the CoP/Fe^(2+)/AM1.5 system.The controllable formation of surface 1O_(2) and·OH_(ads) was achieved through the oxidation(Co^(3+))and reduction(Pδ−)centers exposed on the CoP surface,and the synergistic effect between them results in phenol’s hydroxylation,ring-opening,and degradation.The study of this new mechanism provides a new perspective for revealing the surface interface reaction between ROS and organic pollutants.

In situ studies on ceria promoted cobalt oxide for CO oxidation

In situ studies of catalysts play valuable roles in observing phase transformation, understanding the corresponding surface chemistry and the mechanism of the reaction. In this paper, ceria promoted cobalt oxide was prepared by the calcination method and investigated for the CO oxidation. The microstructure and morphology of CeO2-Co3O4 were investigated by the Scanning Electron Microscope, High-resolution transmission electron microscopy, Raman and X-ray photoelectron spectroscopy characterization. The effect of CeO2 doping on Co3O4 for CO oxidation was characterized by in situ X-ray Diffraction (in situ XRD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). In situ XRD was carried out under H2 atmosphere to evaluate the redox property of catalysts. The results indicated that the ceria doping can enhance the reducibility of Co2+ and promote the Co3+-Co2+-Co3+ cycle, owing to the oxygen replenish property of CeO2. Furthermore, adsorbed carbonate species on the surface of CeO2-Co3O4 were investigated by in situ-DRIFTS experiment. It was turned out that carbonate species on ceria promoted cobalt oxide catalysts showed different IR peaks compared with pure cobalt oxide. The carbonate species on ceria promoted catalyst are more active, and similar to free state carbonate species with weak bonding to catalyst surface, which can effectively inhibit catalyst inactivation. This study revealed the mechanism of ceria promoting CO oxidation over cobalt oxide, which will provide theoretical support for the design of efficient CO oxidation catalysts.

Gold-loaded graphene oxide/PDPB composites for the synchronous removal of Cr(Ⅵ) and phenol

The construction of novel inorganic‐organic hybrid nanomaterials for synchronous photocatalyticremoval of heavy metal ions and organic pollutants has received significant attention.We successfullysynthesized gold‐loaded graphene oxide/PDPB(polymer poly(diphenylbutadiyne))composites(Au‐GO/PDPB)through a facile mechanical agitation and photoreduction method.The compositeswere characterized by XPS and TEM images,which confirmed the presence of GO and Au nanoparticleson the PDPB.The as‐prepared Au‐GO/PDPB composites displayed enhanced photocatalytic activity compared with that of pure PDPB for the synchronous photoreduction of hexavalent chromium(Cr(VI))and photo‐oxidation of phenol.We also determined the optimal loading mass of GO and Au nanoparticles on the PDPB;the Au1‐GO2/PDPB(2.0wt%GO and1.0wt%Au)composite displayed the best photocatalytic activity among all the catalysts.Our study provides a facile way to prepare inorganic‐organic composites for the synchronous photocatalytic removal of heavy metal ions and organic pollutants.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

Graphene-Based Photo-Fenton Catalysts for Pollutant Control

Water pollution is a global environmental issue with multi-dimensional infl uences on human life.Some strategies,such as photo-Fenton reaction,have been employed to remove recalcitrant pollutants.Two-dimensional(2D)graphene and its threedimensional(3D)confi gurations have attracted considerable attention as emerging carbon-based catalysts in photo-Fenton fi elds owing to their alluring properties in electron transfer,reactant adsorption,and light response.This review summarizes the recent developments in 2D and 3D graphene-based catalysts for photo-Fenton reactions.Their structures,characteristics,activity,and mechanisms are discussed.The conclusions and outlooks are proposed for the profound understanding of challenges and future directions.

Regulating Lewis Acid-Base Sites over Fenton System for Enhancing Degradation of Pollutants in Saline and Buffered Wastewater

The saline and buffered environment in actual wastewater imposes higher demands on Fenton and Fenton-like catalytic systems.This study developed a MoS_(2)co-catalytic Fe_(2)O_(3)Fenton-like system with controllable Lewis acid-base sites,achieving efficient treatment of various model pollutants and actual industrial wastewater under neutral buffered environment.The acidic microenvironment structured by the edge S sites(Lewis basic sites)in the MoS_(2)/Fe_(2)O_(3)catalyst is susceptible to the influence of Lewis acidic sites constructed by Mo and Fe element,affecting catalytic performance.Optimizing the ratio of precursor amounts ensures the stable presence of the acidic microenvironment on the surface of catalyst,enabling the beneficial co-catalytic effect of Mo sites to be realized.Furthermore,it transcends the rigid constraints imposed by the Fenton reaction on reaction environments,thereby expanding the applicability of commonplace oxides such as Fe_(2)O_(3)in actual industrial water remediation.

Efficient Fe（Ⅲ）/Fe（Ⅱ） cycling triggered by MoO2 in Fenton reaction for the degradation of dye molecules and the reduction of Cr（Ⅵ）

There is a relatively low efficiency of Fe(Ⅲ)/Fe(Ⅱ) conversion cycle and H2 O2 decomposition(<30%) in conventional Fenton process,which further results in a low production efficiency of ·OH and seriously restricts the application of Fenton.Herein,we report that the commercial MoO2 can be used as the cocatalyst in Fenton process to dramatically accelerate the oxidation of Lissamine rhodamine B(L-RhB),where the efficiency of Fe(Ⅲ)/Fe(Ⅱ) cycling is greatly enhanced in the Fenton reaction meanwhile.And the L-RhB solution could be degraded nearly 100% in 1 min in the MoO2 cocatalytic Fenton system under the optimal reaction condition,which is apparently better than that of the conventional Fenton system(~50%).Different from the conventional Fenton reaction where the ’OH plays an important role in the oxidation process,it shows that 1 O2 contributes most in the MoO2 cocatalytic Fenton reaction.However,it is found that the exposed Mo^4+ active sites on the surface of MoO2 powders can greatly promote the rate-limiting step of Fe^3+/Fe^2+ cycle conversion,thus minimizing the dosage of H2 O2(0.400 mmol/L) and Fe^2+(0.105 mmol/L).Interestingly,the MoO2 cocatalytic Fenton system also exhibits a good ability for reducing Cr(Ⅵ) ions,where the reduction ability for Cr(Ⅵ) reaches almost 100% within 2 h.In short,this work shows a new discovery for M002 cocatalytic advanced oxidation processes(AOPs),which devotes a lot to the practical water remediation application.

Research progress of photocatalysis based on highly dispersed titanium in mesoporous SiO_2

With the development of the human economy and green chemistry, people pay much more attention to environmental safety. Correspondingly, mesoporous TiO_2 and its correlated photocatalysts are able to help people seek for better life. In this review, first of all, we briefly introduce the preparations and applications of mesoporous TiO_2-SiO_2 materials, which exhibit excellent performance in pollutants decomposition and H_2 evolution in photocatalysis. Then, we review the mesoporous composites of TiSiO_2 materials, which are ideal materials used in the photoreduction of air pollutants such as CO_2, NO and NO_2. It is powerfully evident from the literature surveys that these TiO_2 based mesoporous photocatalysts possess a large potential in environment and energy development.

Hollow Fe3O4/carbon with surface mesopores derived from MOFs for enhanced lithium storage performance

Hollow metal-organic frameworks(MOFs)and their derivatives have attracted more and more attention due to their high specific surface area and perfect morphological structure,which determine their large potential application in energy storage and catalysis fields.However,few researchers have carried out further modification on the outer shell of hollow MOFs,such as the perforation modification,which will endow hollow nanomaterials derived from MOFs with multifunctionality.In this paper,hollow MOFs of MIL-53(Fe)with perforated outer surface are successfully synthesized by using SiO2 nanospheres as the template via a self-assembly process induced by the coordination polymerization.The tightly packed mesopore structure makes the carbon outer shell of MOFs thinner,thus realizing the in-situ transformation from MOFs to hollow Fe3 O4/carbon,which exhibits perfect capacity approaching 1270 mA h g-1 even after 200 cycles at 0.1 A g-1,as an anode material in lithium ion batteries(LIBs)application.This research provides a new strategy for the design and preparation of MOFs and their derivatives with multifunctionality for the energy applications.

Sustainable activation of peroxymonosulfate by the Mo(Ⅳ)in MoS_(2) for the remediation of aromatic organic pollutants

Although MoS_(2) has been proved to be a very ideal cocatalyst in advanced oxidation process(AOPs),the activation process of peroxy mono sulfate(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 MoS_(2),as a durable and efficient catalyst,was used for directly activating PMS to degrade aromatic organic pollutant.The commercial MoS_(2)/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 MoS_(2) was directly carried out the next cycle experiment without any post-treatment.Interestingly,the commercial MoS_(2) after post-treated with H2 O_(2) 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 MoS_(2) 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 MoS_(2) catalytic system is expected to be applied in industrial wastewater.

Research progress of graphene-based nanomaterials for the environmental remediation

Graphene is a two-dimensional nanomaterial with huge surface area,high carrier mobility and high mechanical strength.Because of its great potential in nanotechnology and environmental protection,it has attracted much attention in environmental and energy fields since its discovery in 2004.Although graphene is a star material,many reviews have introduced its use in terms of energy,the research progress in the field of environment,especially water pollution control,has been rarely reported.Here,we review exhaustively the research progress of graphene-based materials in environmental pollution remediation in the past ten years.Firstly,the advantages and classification of graphene were introduced.Secondly,the research progress and main achievements of graphene and its composites in the fields of photocatalytic degradation,pollutant adsorption and water treatment were emphatically described,and the mechanism of action in the above fields was summarized.Finally,we discuss the problems existing in the preparation and summarize the application of graphene in the environment.

Defect electrons accelerate iron cycle of novel Fe-based Fenton:Long-term effective quinoline degradation

Heterogeneous Fenton has been widely used in the disposal of organic pollutants,however,slow regeneration of≡Fe(II)remains limitation for its practical application of long-term treatment.Herein,we come up with a novel Fe-based heterogeneous Fenton catalyst named as FeS_(x)O_(y)-X(X is the ratio of ethylene glycol to N,N-dimethylformamide).With the help of the abundant defect electrons in Sulfur vacancies,≡Fe(Ⅱ)regeneration on the surface of FeS_(x)O_(y)-1:1 was accelerated,resulting in a stable proportion of≡Fe(Ⅱ)on the surface,which maintained continuously stable generation of hydroxyl radical(·OH)and singlet oxygen(^(1)O_(2)).Thus,without any organic reagents or cocatalysts,FeS_(x)O_(y)-1:1 based Fenton system achieved effective long-term degradation of 560 mg/L quinoline within only 7 days,which was evidently better than reported Fe S and SV-Fe S_(2)(SV:Sulfur vacancy).The system had excellent adaptability to water quality and the COD removal rate of biochemical wastewater was as high as 79.8%.

Z-scheme CdS/WO_(3)on a carbon cloth enabling effective hydrogen evolution

Photocatalytic water splitting for hydrogen(H2)generation is a potential strategy to solve the problem of energy crisis and environmental deterioration.However,powder-like photocatalysts are difficult to recycle,and the agglomeration of particles would affect the photocatalytic activity.Herein,a direct Z-scheme CdS/WO_(3)composite photocatalyst was fabricated based on carbon cloth through a two-step process.With the support of carbon cloth,photocatalysts tend to grow uniformly for further applications.The experimental results showed that the H2 yield of adding one piece of CdS/WO_(3)composite material was 17.28μmol/h,which was 5.5 times as compared to that of pure CdS-loaded carbon cloth material.A cycle experiment was conducted to verify the stability of the asprepared material and the result demonstrated that the H2 generation performance of CdS/WO_(3)decreased slightly after 3 cycles.This work provides new ideas for the development of recyclable photocatalysts and has a positive significance for practical applications.

"Small amount for multiple times" of H_(2)O_(2) feeding way in MoS_(2)-Fex heterogeneous fenton for enhancing sulfadiazine degradation

In recent years, MoS_(2) catalyzed/cocatalyzed Fenton/Fenton-like systems have attracted wide attention in the field of pollution control, but there are few studies on the effect of H_(2)O_(2) feeding way on the whole Fenton process. Here, we report a new type of composite catalyst (MoS_(2)-Fe_(x)) prepared in a simple way with highly dispersed iron to provide more active sites. MoS_(2)-Fe_(x) was proved to possess selectivity for singlet oxygen (^(1)O_(2)) in effectively degrading sulfadiazine with a wide pH adaptability (4.0~10.0). Importantly, the mechanism of the interaction between H_(2)O_(2) and MoS_(2) on the Fenton reaction activity was revealed through the combination of experiment and density functional theory (DFT) calculations. Compared to the traditional “a large amount for one time” feeding way of H_(2)O_(2), the “small amount for multiple times” of H_(2)O_(2) feeding way can increase the degradation rate of sulfadiazine from 36.9% to 91.1% in the MoS_(2)-Fe_(x) heterogeneous Fenton system. It is demonstrated that the “small amount for multiple times” of H_(2)O_(2) feeding way can reduce the side reaction of decomposition of H_(2)O_(2) by MoS_(2) and effectively improve the utilization rate of H_(2)O_(2) and the stability of MoS_(2)-Fe_(x). Compared with Fe_(2)O_(3)^(-)based Fenton system, MoS_(2)-Fe_(x) can significantly save the amount of H_(2)O_(2). Compared with nano-iron powder, the formation of iron sludge in MoS_(2)-Fe_(x) system was significantly reduced. Furthermore, long-term degradation test showed that the MoS_(2)-Fe75/H_(2)O_(2) system could maintain the effectiveness of degrading organic pollutants for 10 days (or even longer). This study has a guiding significance for the large-scale treatment of industrial wastewater by improved Fenton technology in the future.