Mass Transfer-Promoted Fe^(2+)/Fe^(3+)Circulation Steered by 3D Flow-Through Co-Catalyst System Toward Sustainable Advanced Oxidation Processes

Realizing fast and continuous generation of reactive oxygen species(ROSs)via iron-based advanced oxidation processes(AOPs)is significant in the environmental and biological fields.However,current AOPs assisted by co-catalysts still suffer from the poor mass/electron transfer and non-durable promotion effect,giving rise to the sluggish Fe^(2+)/Fe^(3+)cycle and low dynamic concentration of Fe^(2+)for ROS production.Herein,we present a three-dimensional(3D)macroscale co-catalyst functionalized with molybdenum disulfide(MoS_(2))to achieve ultra-efficient Fe^(2+)regeneration(equilibrium Fe^(2+)ratio of 82.4%)and remarkable stability(more than 20 cycles)via a circulating flow-through process.Unlike the conventional batch-type reactor,experiments and computational fluid dynamics simulations demonstrate that the optimal utilization of the 3D active area under the flow-through mode,initiated by the convectionenhanced mass/charge transfer for Fe^(2+)reduction and then strengthened by MoS_(2)-induced flow rotation for sufficient reactant mixing,is crucial for oxidant activation and subsequent ROS generation.Strikingly,the flow-through co-catalytic system with superwetting capabilities can even tackle the intricate oily wastewater stabilized by different surfactants without the loss of pollutant degradation efficiency.Our findings highlight an innovative co-catalyst system design to expand the applicability of AOPs based technology,especially in large-scale complex wastewater treatment.

UV-Based Advanced Oxidation Processes for Antibiotic Resistance Control: Efficiency, Influencing Factors, and Energy Consumption

Antibiotic resistant bacteria(ARB)with antibiotic resistance genes(ARGs)can reduce or eliminate the effectiveness of antibiotics and thus threaten human health.The United Nations Environment Programme considers antibiotic resistance the first of six emerging issues of concern.Advanced oxidation processes(AOPs)that combine ultraviolet(UV)irradiation and chemical oxidation(primarily chlorine,hydrogen peroxide,and persulfate)have attracted increasing interest as advanced water and wastewater treatment technologies.These integrated technologies have been reported to significantly elevate the efficiencies of ARB inactivation and ARG degradation compared with direct UV irradiation or chemical oxidation alone due to the generation of multiple reactive species.In this study,the performance and underlying mechanisms of UV/chlorine,UV/hydrogen peroxide,and UV/persulfate processes for controlling ARB and ARGs were reviewed based on recent studies.Factors affecting the process-specific efficiency in controlling ARB and ARGs were discussed,including biotic factors,oxidant dose,UV fluence,pH,and water matrix properties.In addition,the cost-effectiveness of the UV-based AOPs was evaluated using the concept of electrical energy per order.The UV/chlorine process exhibited a higher efficiency with lower energy consumption than other UV-based AOPs in the wastewater matrix,indicating its potential for ARB inactivation and ARG degradation in wastewater treatment.Further studies are required to address the trade-off between toxic byproduct formation and the energy efficiency of the UV/chlorine process in real wastewater to facilitate its optimization and application in the control of ARB and ARGs.

Fabrication of pollution-free coal gangue-based catalytic material utilizing ferrous chloride as activator for efficient peroxymonosulfate activation

Novel coal gangue-based persulfate catalyst(CG-FeCl_(2))was successfully synthesized by the means of calcinating under nitrogen atmosphere with the addition of ferrous chloride tetrahydrate(FeCl_(2)·_(4)H_(2)O).The phase transformation of the prepared materials and gas products during the heating process are thoroughly investigated.It is suggested that ferrous chloride participated in the phase transformation and formed Si-O-Fe bonds.And the main gaseous products are H_(2)O,H_(2),and HCl during the heating process.Besides,the ability of CG-FeCl_(2) to activate peroxymonosulfate(PMS)for catalytic degradation of polycyclic aromatic hydrocarbons(PAHs)and phenol was deeply studied.More than 95%of naphthyl,phenanthrene and phenol were removed under optimizied conditions.In addition,1O_(2),·OH,and SO_(4)·−were involved in the CG-FeCl_(2)/PMS system from the free radical scavenging experiment,where 1O_(2) played a major role during the oxidation process.Furthermore,CG-FeCl_(2)/PMS system exhibited superior stability in a relatively wide pH range and the presence of common anion from related degradation experiments.Overall,the novel CG-FeCl_(2) is an efficient and environmentally friendly catalyst,displaying potential application prospect in the field of PAHs and phenol-contaminated wastewater treatment.

A novel advanced oxidation process to degrade organic pollutants in wastewater:Microwave-activated persulfate oxidation

This article, for the first time, provides a novel advanced oxidation process based on sulfate radical （SO^4·-） to degrade organic pollutants in wastewater： microwave （MW）-activated persulfate oxidation （APO） with or without active carbon （AC）. Azo dye acid Orange 7 （AO7） is used as a model compound to investigate the high reactivity of MW-APO. It is found that AO7 （up to 1000 mg/L） is completely decolorized within 5-7 min under an 800 W MW furnace assisted-APO. In the presence of chloride ion （up to 0.50 mol/L）, the decolorization is still 100% completed, though delayed for about 1-2 min. Experiments are made to examine the enhancement by AC. It is exciting to find that the 100% decolorization of AO7 （500 mg/L） is achieved within 3 min by MW-APO using 1.0 g/L AC as catalyst, while the degradation efficiency maintains at 50% by MW energy without persulfate after about 5 min. Besides the destruction of visible light chromophore band of AO7 （484 nm）, during MW-APO, two bands in the ultraviolet region （228 nm and 310 nm） are rapidly broken down. The removal of COD is about 83%-95% for 500 mg/L AO7. SO^4·- is identified with quenching studies using specific alcohols. Both SO^4·- and ·OH could degrade AO7, but SO^4·- plays the dominant role. In a word, MW-APO AC is a new catalytic combustion technology for destruction of organic contamination even for high concentration.

Application of advanced oxidation processes for removing salicylic acid from synthetic wastewaters

In this study,advanced oxidation processes(AOPs) such as anodic oxidation(AO),UV/H_2O_2 and Fenton processes(FP) were investigated for the degradation of salicylic acid(SA) in lab-scale experiments.Boron-doped diamond(BDD) film electrodes using Ta as substrates were employed for AO of SA.In the case of FP and UV/H_2O_2,most favorable experimental conditions were determined for each process and these were used for comparing with AO process.The study showed that the FP was the most effective process under aci...

Chemical oxygen demand reduction in coffee wastewater through chemical flocculation and advanced oxidation processes

The removal of the natural organic matter present in coffee processing wastewater through chemical coagulation-flocculation and advanced oxidation processes （AOP） had been studied. The effectiveness of the removal of natural organic matter using commercial flocculants and UV/H202, UV/O3 and UV/H2O2/O3 processes was determined under acidic conditions. For each of these processes, different operational conditions were explored to optimize the treatment efficiency of the coffee wastewater. Coffee wastewater is characterized by a high chemical oxygen demand （COD） and low total suspended solids. The outcomes of coffee wastewater treatment using coagulation-flocculation and photodegradation processes were assessed in terms of reduction of COD, color, and turbidity. It was found that a reduction in COD of 67% could be realized when the coffee wastewater was treated by chemical coagulation-flocculation with lime and coagulant T-1. When coffee wastewater was treated by coagulation-flocculation in combination with UV/H2O2, a COD reduction of 86% was achieved, although only after prolonged UV irradiation. Of the three advanced oxidation processes considered, UV/H2O2, UV/O3 and UV/H2O2/O3, we found that the treatment with UV/H2O2/O3 was the most effective, with an efficiency of color, turbidity and further COD removal of 87%, when applied to the flocculated coffee wastewater.

O_(3) based advanced oxidation for ibuprofen degradation

The degradation of the anti-inflammatory ibuprofen(IBP)was evaluated by several advanced oxidation processes.IBP was treated by single ozonation and oxidation with hydrogen peroxide(H_(2)O_(2)),as well as a combination of these treatments.In order to improve the efficiency,the presence of catalysts such as original carbon nanotubes,labelled as CNT,and iron oxide supported on carbon nanotubes,named as Fe/CNT sample,was considered.The evolution of IBP degradation,mineralization and toxicity of the solutions was assessed.The formation of intermediates was also monitored.In the non-catalytic processes,IBP was faster removed by single ozonation,whereas no significant total organic carbon(TOC)removal was achieved.Oxidation with H_(2)O_(2) did not present satisfactory results.When ozone and H_(2)O_(2) were combined,a higher mineralization was attained(70%after 180 min of reaction).On the other hand,in the catalytic processes,this combined process allowed the fastest IBP degradation.In terms of mineralization degree,the presence of Fe/CNT increases the removal rate in the first hour of reaction,achieving a TOC removal of 85%.Four compounds were detected as by-products.All treated solutions presented lower toxicity than the initial solution,suggesting that the released intermediates during applied processes are less toxic.

Acid precipitation coupled membrane-dispersion advanced oxidation process(MAOP)to treat crystallization mother liquor of pulp wastewater

Treatment to crystallization mother liquor containing high concentration of organic and inorganic substances is a challenge in zero liquid discharge of industrial wastewater.Acid precipitation coupled membrane-dispersion advanced oxidation process(MAOP)was proposed for organics degradation before salt crystallization by evaporation.With acid-MAOP treatment CODCrin mother liquor of pulping wastewater was eliminated by 55.2%from ultrahigh initial concentration up to 12,500 mg·L^-1.The decolorization rate was 96.5%.Recovered salt was mainly NaCl(83.3 wt%)having whiteness 50 brighter than industrial baysalt of whiteness 45.The oxidation conditions were optimized as CO3=0.11 g·L^-1 and CH2O2=2.0 g·L^-1 with dispersing rate 0.53 ml·min^-1 for 100 min reaction toward acidified liquor of p H=2.Acidification has notably improved evaporation efficiency during crystallization.Addition of H2O2 made through membrane dispersion has eliminated hydroxyl radical"quench effect"and enhanced the degradation capacity,in particular,the breakage of carbon-chloride bonds(of both aliphatic and aromatic).As a result,the proposed coupling method has improved organic pollutant reduction so as the purity of salt from the wastewater mixture which can facilitate water and salt recycling in industry.

Performance of a Demonstrative (Scale-Pilot) Double Advanced Oxidation Wastewater Treatment Plant to Treat Discharges from a Small Community in Morelia, Michoacán, México

This paper,reports the performance of a wastewater treatment scale-pilot plant to treat 2 GPM(Gallons per Minute)discharges with 5,205 mg/L of pollutants expressed in COD(Chemical Oxygen Demand),from“Lomas de la Maestransa”a small community in Morelia City,Michoacan,Mexico.The scale-pilot plant is a train with(1)pretreatment with a triturated pump for floating solid,(2)primary treatment with“in line”coagulation,and rapid filtration to retain suspended colloids and dissolved solids higher of 5μm diameter,(3)double advanced oxidation as secondary treatment with ozone and heterogeneous photo catalysis to oxidize volatile solids,and(4)tertiary treatment with activated carbon to retain refractory compounds.Plant performance was analyzed by a certified laboratory that belongs to Potable Water,Sewage and Sanitation Department from Morelia City Government.Results show that treated water effluent complied with the Mexican Official Standard NOM-001-SEMARNAT-1996 for discharges into national waters,with exception of fecal coliforms,since the raw water contains an average of 64,228,351 MNP/100 mL of fecal coliforms,and in spite that we obtained a 99.998%efficiency,the maximum level allowable 2,000 MPN/100 mL standard,was exceeded by 400 MPN/100 mL.After this experience,the wastewater treatment plant is equipped with a residual chlorine tank to keep a 1.5 ppm chlorine residual concentration to keep the treated water clean.This project was possible because we had the support of the Morelia Sanitation Department.

Effects of Advanced Oxidation Processes on the Decomposition Properties of Organic Compounds with Different Molecular Structures in Water

Studies to decompose persistent organic pollutants in wastewater from chemical factories by using Advanced Oxidation Processes (AOPs) have recently been performed. Oxidation reactions involving ozone and •OH radicals and cleavage caused by UV are the main decomposition reactions that occur in AOPs using ozone and UV. The mechanisms through which organic compounds are decomposed in AOPs are complicated and difficult to understand because various decomposition reactions occur simultaneously. The Total Organic Carbon (TOC) removal efficiencies achieved in several different AOPs were evaluated in this study. The TOC removal efficiencies were different for organic compounds with different chemical structures. The TOC was more effectively removed when aromatic compounds were treated using the O3-UV-TiO2 process than when using the other AOPs, and the TOC was removed more effectively by the O3-UV process than by the UV-TiO2 process. However, the TOC was removed more effectively when open-chain compounds were treated using the UV-TiO2 process than using the O3-UV process, and the UV-TiO2 and O3-UV-TiO2 processes resulted in similar TOC removal efficiencies. Therefore, it is necessary to use the O3-UV-TiO2 process to decompose aromatic compounds as quickly as possible. On the other hand, the UV-TiO2 process degraded the open-chain compounds most effectively, and the O3-UV-TiO2 process did not need to decompose open-chain compounds. Moreover, the TOC of aromatic compounds was removed more slowly than that of open-chain compounds. The TOC removal efficiency increased with decreasing the number of carbon atoms in the molecule. The TOC removal efficiencies increased in order of the organic compounds containing methyl groups, aldehyde groups and carboxyl groups. The removal of the TOC when organic compounds were treated using the O3-UV-TiO2 process followed pseudo-zero-order kinetics.

Two-dimensional nanomaterials confined single atoms: New opportunities for environmental remediation

Two-dimensional(2D)supports confined single-atom catalysts(2D SACs)with unique geometric and electronic structures have been attractive candidates in different catalytic applications,such as energy conversion and storage,value-added chemical synthesis and environmental remediation.However,their environmental appli-cations lack of a comprehensive summary and in-depth discussion.In this review,recent progresses in synthesis routes and advanced characterization techniques for 2D SACs are introduced,and a comprehensive discussion on their applications in environmental remediation is presented.Generally,2D SACs can be effective in catalytic elimination of aqueous and gaseous pollutants via radical or non-radical routes and transformation of toxic pollutants into less poisonous species or highly value-added products,opening a new horizon for the contami-nant treatment.In addition,in-depth reaction mechanisms and potential pathways are systematically discussed,and the relationship between the structure-performance is highlighted.Finally,several critical challenges within this field are presented,and possible directions for further explorations of 2D SACs in environmental remediation are suggested.Although the research of 2D SACs in the environmental application is still in its infancy,this review will provide a timely summary on the emerging field,and would stimulate tremendous interest for designing more attractive 2D SACs and promoting their wide applications.

Review of advanced oxidation processes for treating hospital sewage to achieve decontamination and disinfection

Hospital sewage contains various harmful pharmaceutical contaminants(e.g.,antibiotics,anti-inflammatory agents,and painkillers)and pathogens(e.g.,bacteria,viruses,and parasites),whose direct discharge into the environment will induce diseases and pose a powerful threat to human health and safety,and environmental ecology.In recent years,advanced oxidation processes(AOPs),particularly photocatalysis,electrocatalysis,and ozone catalysis have been developed as widespread and effective techniques for hospital sewage treatments.However,there is a lack of systematic comparison and review of the prior studies on hospital sewage treatment using AOPs systems.This review elaborates on the mechanisms,removal efficiencies,and advantages/disadvantages of these AOPs systems for hospital wastewater decontamination and disinfection.Meanwhile,some novel and potential technologies such as photo-electrocatalysis,electro-peroxone,Fenton/Fenton-like,and piezoelectric catalysis are also included and summarized.Moreover,we further summarize and compare the capacity of these AOPs to treat the actual hospital wastewater under the impact of the water matrix and pH,and estimate the economic cost of these technologies for practical application.Finally,the future development directions of AOPs for hospital wastewater decontamination and disinfection have been prospected.Overall,this study provides a comparison and overview of these AOP systems in an attempt to raise extensive concerns about hospital wastewater decontamination and disinfection technologies and guide researchers to discover the future directions of technologies optimization,which would be a crucial step forward in the field of hospital sewage treatment.

Sustainable Generation of Sulfate Radicals and Decontamination of Micropollutants via Sequential Electrochemistry

The removal of emerging micropollutants in the aquatic environment remains a global challenge.Conventional routes are often chemically,energetically,and operationally intensive,which decreases their sustainability during applications.Herein,we develop an advanced chemical-free strategy for micropollutants decontamination that is solely based on sequential electrochemistry involving ubiquitous sulfate anions in natural and engineered waters.This can be achieved via a chain reaction initiated by electrocatalytic anodic sulfate(SO_(4)^(2-))oxidation to produce persulfate(S_(2)O_(8)^(2-))and followed by a cathodic persulfate reduction to produce sulfate radicals(SO_(4)^(·-)).These SO_(4)^(·-)are powerful reactive species that enable the unselective degradation of micropollutants and yield SO_(4)^(2-)again in the treated water.The proposed flow-through electrochemical system achieves the efficient degradation(100.0%)and total organic carbon removal(65.0%)of aniline under optimized conditions with a single-pass mode.We also reveal the effectiveness of the proposed system for the degradation of a wide array of emerging micropollutants over a broad pH range and in complex matrices.This work provides the first proof-ofconcept demonstration using ubiquitous sulfate for micropollutants decontamination,making water purification more sustainable and more economical.

Influence of MnO_(x)deposition on TiO_(2)nanotube arrays for electrooxidation

TiO_(2)has demonstrated outstanding performance in electrochemical advanced oxidation processes(EAOPs)due to its structural stability and high oxygen overpotential.However,there is still much room for improving its electrochemical activity.Herein,narrow bandgap manganese oxide(MnO_(x))was composited with TiO_(2)nanotube arrays(TiO_(2)NTAs)that in-situ oxidized on porous Ti sponge,forming the MnO_(x)-TiO_(2)NTAs anode.XANES and XPS analysis further proved that the composition of MnO_(x)is Mn2O3.Electrochemical characterizations revealed that increasing the composited concentration of MnO_(x)can improve the conductivity and reduce oxygen evolution potential so as to improve the electrochemical activity of the composited MnO_(x)-TiO_(2)NTAs anode.Meanwhile,the optimal degradation rate of benzoic acid(BA)was achieved using MnO_(x)-TiO_(2)NTAs with a MnO_(x)concentration of 0.1 mmol L^(-1),and the role of MnO_(x)was proposed based on DFT calculation.Additionally,the required electrical energy(EE/O)to destroy BA was optimized by varying the composited concentration of MnO_(x)and the degradation voltage.These quantitative results are of great significance for the design and application of high-performance materials for EAOPs.

Rapid Degrading Carbamazepine in a Novel Advanced Oxidation Process of Bisulfite Activated by Lithium Cobaltate Recovered from Spent Lithium-ion Battery

Maximizing the sustainable recycling of spent lithium-ion batteries(LIBs)shows economic and environmental significance.This study recovered lithium cobaltate(LiCoO_(2),LCO)from spent LIBs cathode powder.The recovered LCO was then combined with NaHSO_(3)to remove refractory organic pollutants of carbamazepine(CBZ)in water.The degradation of CBZ reached 80.0%within 60 min,by 1O_(2),SO_(4),OH and O_(2)^(-)generated in the LCO/NaHSO_(3)reaction.The electron transfer between Co(III)and Co(II)was beneficial to the generation of free radicals.The LCO/NaHSO_(3)degraded CBZ effectively in both secondary outlet water and tap water.However,high concentrations of inorganic ions(Cl^(−),HCO_(3)^(-),HPO_(4)^(2-),SO_(2)−4,NO_(3)^(-))and natural organic matter(humic acid,HA)could inhibit the degradation of CBZ.After three cycles,the stability of the LCO/NaHSO_(3)system was demonstrated by the maintained high efficiency in the degradation of CBZ.The obtained data indicate that the LCO/NaHSO_(3)system holds great application potential in the field of advanced oxidation degradation of pollutants.

Manganese oxide and derivative-modified materials in advanced oxidation processes:A review of modification enhancement and activation mechanisms

Manganese oxides(MNO_(x)),as low-toxicity and high-abundance catalysts,have been demonstrated to hold great promise for application in advanced oxidation processes(AOPs).However,further application of this material is restricted due to its unsatisfactory oxidant activation efficiency.Fortunately,recently remarkable research on deep activation mechanisms and modification of MNO_(x)have been undertaken to improve its reactivity.Herein,modification enhancement mechanisms of MNO_(x)to efficiently degrade various organic contaminants were discussed and highlighted,including metal doping,coupling with other metal oxides,composite with carbonaceous material,and compounding with other support.The activation mechanisms of different MNO_(x)and derivative-modified material(such as doped MNO_(x),metal oxide-MNO_(x)hybrids,and MNO_(x)-carbonaceous material hybrids)were summarized in great details,which was specifically categorized into both radical and non-radical pathways.The effects of pH,inorganic ions,and natural organic matter on degradation reactions are also discussed.Finally,future research directions and perspectives are presented to provide a clear interpretation on the MNO_(x)initiated AOPs.

Recent advances on decomplexation mechanisms of heavy metal complexes in persulfate-based advanced oxidation processes

In some industrial wastewater,heavy metals combine with organic complexing agents to form heavy metal complexes(HMCs).These HMCs can be difficult to decompose and remove through conventional techniques due to their higher stability than free heavy metal ions.In recent years,persulfate based advanced oxidation processes(PS-based AOPs)have been recognized as a viable technique for HMCs degradation.Nevertheless,a comprehensive and in-depth understanding of the relevant HMCs decomplexation mechanisms in PS-based AOPs is still lacking.This review delineates the current progress of HMCs decomplexation in PS-based AOPs.We discuss the distinctions between the two widely used oxidant types in PS-based AOPs techniques.Moreover,we summarize and highlight the decomplexation mechanisms based on electron and energy transfer,and degradation pathways of HMCs.We also emphasize the effects of environmental water constituents,namely p H,inorganic ions,and natural organic matter(NOM),on HMCs decomplexation.Ultimately,we identify the existing challenges and perspectives that will steer the direction of advancing PS-based AOPs to remove HMCs.

Photocatalytic Degradation of Oxytetracycline Dihydrate from Aqueous Solution Using Nano ZnO and ZnO.xBaTiO3 (x = 3%, 18%, 33% and 48%)

Traditional wastewater mostly contains pharmaceutical ingredients. Therefore, the wastewater must be completely free from antibiotics before its release into the environment. In the present study, photocatalytic degradation was done to investigate the removal efficiency of Oxytetracycline Dihydrate (OTC) using ZnO, ZnO/3%BaTiO3 (3 BZ), ZnO/18%BaTiO3 (18 BZ), ZnO/ 33%BaTiO3 (33 BZ) and ZnO/48%BaTiO3 (48 BZ) under UV light. After the exposure time of 420 min, about 99.57% and 97.87% of OTC was degraded using ZnO and 3 BZ respectively. Further, increasing the amount of BaTiO3 in ZnO prolongs the degradation time. Therefore, faster efficiency was found using ZnO nanoparticles. The observed reaction rate constant using ZnO was 0.00933 min-1 which decreased to 0.00532 min-1 using 48 BZ, indicating the decrease of reaction rate for increasing the amount of BaTiO3. Hence, the use of ZnO photocatalyst is anticipated to be a promising technique for the photocatalytic degradation of contaminated wastewater with oxytetracycline antibiotics using UV light.

Degradation of 2,4-dichlorophenoxyacetic acid in water by ozonehydrogen peroxide process

This study reports an investigation into the degradation of 2,4-dichlorophenoxyacetic acid in bubble contactor column by O2/H2O2 process, which is widely used as a principal advanced oxidation process. The degradation of 2,4-dichlorophenoxyacetic acid was studied under different H202/O3 molar ratio and pH value. Meanwhile, TOC removal was investigated both in distilled water and tap water. The influences of ozone transfer and consumed hydrogen peroxide were also discussed. The degradation products and oxidation intermediates were identified by GC-MS and LC-MS. A possible reaction mechanism was thus proposed.

Degradation of nitrobenzene in aqueous solution by ozone-ceramic honeycomb

The degradation of nitrobenzene by ceramic-honeycomb catalyzed ozonation was investigated. The results showed that the presence of ceramic honeycombs significantly increased the oxidation rate of nitrobenzene by ozone compared to the case of ozone oxidation alone. In this paper, the effects of various factors on the catalytic oxidation were investigated, such as the amount of catalysts, the ozone dosage, the temperature, the pH value and the presence of tert-butanol. With the addition of tert-butanol the removal of nitrobenzene decreased sharply, which appeared to support that, the degradation of nitrobenzene by ozonation followed a radical type mechanism. The EPR experiments verified that higher nitrobenzene removal rate was attributed to more OH radicals generated in the catalyzed ozonation than ozonation alone.