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.

Microbial Degradation of Organic Contaminants in Streambed/Floodplain Sediments in Passaic River—New Jersey Area

This paper is intended to explore soil organic matter and carbon isotope fractionation at three locations of the Passaic River to determine if microbial degradation of organic contaminants in soil is correlated to the surrounding physical environment. Microbial degradation of organic contaminants is important for the detoxification of toxic substances thereby minimizing stagnation in the environment and accumulating in the food chain. Since organic contaminants are not easily dissolved in water, they will penetrate sediment and end up enriching the adjacent soil. The hypothesis that we are testing is microbial activity and carbon isotope fractionation will be greater in preserved soils than urban soils. The reason why this is expected to be the case is the expectation of higher microbial activity in preserved environments due to less exposure to pollutants, better soil structure, higher organic matter content, and more favorable conditions for microbial growth. This is contrasted with urban soils, which are impacted by pollutants and disturbances, potentially inhibiting microbial activity. We wish to collect soil samples adjacent to the Passaic River at a pristine location, Great Swamp Wildlife Refuge, a suburban location, Goffle Brook Park, Hawthorne NJ, and an urban location, Paterson NJ. These soil samples will be weighed for soil organic matter (SOM) and weighed for isotope ratio mass spectrometry (IRMS) to test organic carbon isotopes. High SOM and δ13C depletion activity indicate microbial growth based on the characteristics of the soil horizon rather than the location of the soil sample which results in degradation of organic compounds.

A Diamond Electrochemical Cleaning Technique for Organic Contaminants on Silicon Wafer Surfaces

Peroxodiphosphate anion （a powerful oxidant） can be formed in a special water-based cleaning agent through an electrochemical reaction on boron-doped diamond electrodes. This electrochemical reaction was applied during the oxidation,decomposition, and removal of organic contaminations on a silicon wafer surface, and it was used as the first step in the diamond electrochemical cleaning technique （DECT）. The cleaning effects of DECT were compared with the RCA cleaning technique, including the silicon surface chemical composition that was observed with X-ray photoelectron spectroscopy and the morphology observed with atomic force microscopy. The measurement results show that the silicon surface cleaned by DECT has slightly less organic residue and lower micro-roughness,so the new technique is more effective than the RCA cleaning technique.

Nanofiber-based enrichment device for sampling organic contaminants in vacuum environment

A novel method for sampling and enriching organic volatile contaminants in the vacuum environment combined with qualitative analysis based on the vacuum simulation test is proposed. A nanofiber is used as absorbent to collect the organic volatile contaminants in the vacuum environment and then eluted by methanol. The eluent is analyzed by gas chromatography （ GC ） and gas chromatography-mass spectrometry （GC/MS） to identify the composition of the organic contaminants. The nanofiber is composed of polystyrene and it is prepared by electrospinning. Before being used, the nanofiber is processed by ultrasound in ethanol for 15 min to remove some impurities and dried in an oven at 60 ℃, and then 10 mg of the nanofiber is wrapped in a thermoplastic polyester fabric pocket. The vacuum pump oil and di-iso-decyl phthalate （DIDP） are chosen as absorbates to test the absorbent performance of the nanofiber in the vacuum environment. Experiments are performed under the pressure of 10-4 and 103 Pa, respectively. It is shown that the nanofiber-based enrichment device can be used to adsorb the organic contaminants in the vacuum simulation environment.

Surfactant-Enhanced Phytoremediation of Soils Contaminated with Hydrophobic Organic Contaminants:Potential and Assessment

Phytoremediation is becoming a cost-effective technology for the in-situ clean up of sites polluted with hydrophobic organic contaminants （HOCs）. The major factors limiting phytoremediation are the mass transfer, rate of plant uptake, and microbial biodegradation of HOCs. This article discusses the potential of surfactants to enhance desorption, plant uptake, and biodegradation of HOCs in the contaminated sites. Positive effects of surfactants on phytoremediation have been recently observed in greenhouse studies. The presence of some nonionic surfactants including polyoxyethylene sorbltan monooleate （Tween 80） and polyoxyethylene（23）dodecanol （Brij35） at relatively low concentrations resulted in significant positive effects on phytoremediation for pyrene-contaminated soil. However, the anionic surfactant （sodium dodecyl sulfate, SDS） and the cationic surfactant （cetyltrimethylammonium bromide, CTMAB） were not useful because of their phytotoxicity or low efficiency for surfactant-enhanced phytoremediation （SEPR）. The mechanisms of SEPR for HOC-contaminated sites were evaluated by considering experimental observations. In view of concerns about the cost effectiveness and toxicity of surfactants to plants, more research is needed to enhance the use of SEPR technology.

Analysis of diffusion-adsorption equivalency of landfill liner systems for organic contaminants

The equivalence between multilayered barriers regarding diffusion and adsorption was studied. The bottom boundary of the liner system is defined by assuming concentration continuous and flux continuous conditions of the contaminant between the bottom liner layer and the underlying soil. Five different liner systems were compared in terms of solute breakthrough time. The results of the analysis showed that breakthrough time of the hydrophobic organic compounds for a 2-meter-thick compacted clay liner （CCL） could be 3-4 orders of magnitude is greater than the breakthrough time for a geosynthetic clay liner （GCL） composite liner. The GM/GCL and GM/CCL composite liner systems provide a better diffusion barrier for the hydrophilic organic compounds than that for the hydrophobic compounds due to their different Henry＇s coefficient. The calculated breakthrough times of the organic contaminants for the Chinese standard liner systems were found to be generally greater than those for the GCL alternatives, for the specific conditions examined. If the distribution coefficient increases to 2.8 for the hydrophobic compounds or 1.0 for the hydrophilic compounds, the thickness of the attenuation layer needed to achieve the same breakthrough time as the standard liner systems can be reduced by a factor of about 1.9-2.4. As far as diffusive and adsorption contaminant transport are concerned, GM or GCL is less effective than CCL.

Emerging Organic Contaminants in Chinese Surface Water:Identification of Priority Pollutants

The occurrence and impacts of emerging organic contaminants(EOCs)in the aquatic environment have gained widespread attention over the past two decades.Due to large number of potential contaminants,monitoring campaigns,treatment plants,and proposed regulations should preferentially focus on specific pollutants with the highest potential for ecological and human health effects.In the present study,a multi-criteria screening approach based on hazard and exposure potentials was developed for prioritization of 405 unregulated EOCs already present in Chinese surface water.Hazard potential,exposure potential,and risk quotients for ecological and human health effects were quantitatively analyzed and used to screen contaminants.The hazard potential was defined by contaminant persistence,bioaccumulation,ecotoxicity,and human health effects;similarly,the exposure potential was a function of contaminant concentration and detection frequency.In total,123 compounds passed the preselection process,which involved a priority index equal to the normalized hazard potential multiplied by the normalized exposure potential.Based on the prioritization scheme,11 compounds were identified as top-priority,and 37 chemicals were defined as high-priority.The results obtained by the priority index were compared with four other prioritization schemes based on exposure potential,hazard potential,or risk quotients for ecological effects or human health.The priority index effectively captured and integrated the results from the more simplistic prioritization schemes.Based on identified data gaps,four uncertainty categories were classified to recommend:①regular monitoring,derivation of environmental quality standards,and development of control strategies;②increased monitoring;③fortified hazard assessment;and④increased efforts to collect occurrence and toxicity data.Overall,20 pollutants were recommended as priority EOCs.The prioritized list of contaminants provides the necessary information for authoritative regulations to monitor,control,evaluate,and manage the risks of environmentally-relevant EOCs in Chinese surface water.

Selective oxidation of emerging organic contaminants in heterogeneous Fenton-like systems

Heterogeneous Fenton-like reaction shows great potential for eliminating organic substances (e.g. emerging organic contaminants (EOCs)) in water, which has been widely explored in recent decades. However, the catalytic mechanisms reported in current studies are extremely complicated because multiple mechanisms coexist and contribute to the removal efficiencies. Most importantly, heterogeneous systems show selective oxidation properties, which are crucial for improving the efficiencies in the catalytic elimination of organic substances. Thus, this critical review summarizes and compares the diverse existing mechanisms (non-radical and radical pathways) in heterogeneous catalytic processes based on recent studies. The typical oxidation mechanisms during selective advanced oxidation of EOCs were systematically discussed based on the following sections, including the selective adsorption and generation of reactive oxygen species (ROS) in photo/electron-Fenton and Fenton-like systems. Moreover, the non-radical pathways are discussed in depth by the singlet oxygen, high-valent metal-oxo, electron transfer process, etc. Moreover, the direct oxidative transfer process for the removal of EOCs was introduced in recent studies. Finally, the cost, feasibility as well as the sustainability of heterogeneous Fenton-like catalysts are summarized. This review offers useful guidance for developing suitable strategies to develop materials for decomposing the organic substrates.

Characterizing occurrence of emerging organic contaminants in Dinaric karst catchment of Jadro andZrnovnica springs,Croatia

The occurrence of emerging organic contaminants(EOCs)was investigated in vulnerable Dinaric karst catchment of Jadro andZrnovnica springs in Croatia,under varying flow conditions and across three different water resource types(groundwater,springs,and surface water).The maximal EOCs concentration in both springs were observed following autumn recharge events,while during peak discharge no detection above the limits of detection(LOD)was recorded due to dilution process.Contrarily to springs,groundwater from deep borehole exhibited highest total EOCs concentration under low flow conditions,underscoring the considerable karst aquifer vulnerability and its oligotrophic nature.The peak EOCs concentration in karstic Cetina River coincided with the river's lowest discharge.The highest mass flux of 1013 g/day was determined for very mobile pharmaceutical metformin detected in Cetina.The presence of potentially persistent to very persistent compounds,like DEET and 1H-benzotriazole,which exhibited highest detection frequencies across all sampling sites,was observed in association with varying hydrological conditions.Hypotheses regarding the occurrence of identified EOCs include surface contamination infiltrating directly through ponors and highly karstified areas,potential persistence in the epikarst and aquifer matrix,and site-specific contamination sources for compounds such as 1H-benzotriazole,gabapentin,and ketoprofen found in groundwater.To evaluate the risk of inadvertent human exposure to EOCs across various age groups,we utilized measured spring concentrations and calculated drinking water equivalent levels(DWEL),which ranged from 1.4 mg/L for cotinine to 503 mg/L for sucralose,both detected in Jadro spring.Although EOCs concentrations in ng/L are unlikely to pose a significant risk to healthy population,long-term exposure to EOCs mixture remains unknown.Given scarcity of research on EOCs in karst environments on both global and national levels,our study enhances comprehension of their occurrence and behaviour across different karst water resources that hold crucial importance for drinking water supply in regions like Dinarides.

Biochar-based materials and their applications in removal of organic contaminants from wastewater:state-of-the-art review

As a class of famous carbon materials,biochars(BCs)and their derivative materials with excellent physicochemical properties and diversified functionalities present great potential in wastewater treatment fields.This review focuses on the latest development in reported biochar-based materials as superior adsorbents or catalysts for removing harmful organic contaminants from wastewater.The construction and properties of biochar-based materials are briefly introduced at the beginning.As one of the major factors affecting the properties of BCs,the wide diversity of feedstocks,such as agricultural and forest residues,industrial by-products as well as municipal wastes,endows BCs different chemical compositions and structures.Woody and herbaceous BCs usually have higher carbon contents,larger surface areas and strong aromaticity,which is in favor of the organic contaminant removal.Driven by the desire of more cost-effective materials,several types of biochar-based hybrid materials,such as magnetic BC composites(MBC),nanometal/nanometallic oxides/hydroxide BC composites and layered nanomaterial-coated BCs,as well as physically/chemically activated BCs,have also been developed.With the help of foreign materials,these types of hybrid BCs have excellent capacities to remove a wide range of organic contaminants,including organic dyestuff,phenols and chemical intermediates,as well as pharmaceutically active compounds,from aquatic solutions.Depending on the different types of biochar-based materials,organic contaminants can be removed by different mechanisms,such as physical adsorption,electrostatic interaction,π-πinteraction and Fenton process,as well as photocatalytic degradation.In summary,the low cost,tunable surface chemistry and excellent physical-chemical properties of BCs allow it to be a potential material in organic contaminant removal.The combination of BCs with foreign materials endows BCs more functionalities and broader development opportunities.Considering the urgent demand of practical wastewater treatment,we hope more researches will focus on the applications and commercialization of biochar-based materials.

Engineering carbon nanocatalysts towards efficient degradation of emerging organic contaminants via persulfate activation:A review

The engineering of carbon nanocatalysts for the persulfate activated elimination of emerging organic contaminants(EOCs)demonstrates promising potential compared with metal-based counterparts due to their unique advantage of high stability and low toxicity.The early reviews introduced the theoretical background of persulfate activation together with a detailed summary of different mechanisms responsible for degradation of EOCs.To further unify the state of knowledge,identify the research gaps,and prompt new research in this area,we present a thorough review on current trends in research on metal-free carbon nanocatalysts(e.g.,0D nanodiamond,1D carbon nanotubes and carbon nanofibers,2D graphene and graphitic carbon nitride,and 3D carbon nanocatalysts),with emphasis on their applications in persulfate activation and EOCs decontamination.We also discuss the current challenges and future perspectives in practically relevant applications.Last,we highlight that the development of sustainable carbon nanocatalysts/persulfate systems lies at the interface of multiple disciplines,which calls for future in-depth interdisciplinary collaborations.

Coaxial Fe_(2)O_(3)/TiO_(2)nanotubes for enhanced photo-Fenton degradation of electron-deficient organic contaminant

Coaxial Fe_(2)O_(3)/TiO_(2)nanotubes(Fe_(2)O_(3)/TiO_(2)NTs)were prepared by two anodic oxidation processes.The synthesized Fe_(2)O_(3)/TiO_(2)NTs catalysts showed high photocatalytic activity in heterogeneous photo-Fenton system.With the help of Fe_(2)O_(3)/TiO_(2)NTs,4-nitrophenol(10 mg·L^(-1),50 ml),a typical electron-deficient organic contaminant,can be completely removed by adding only0.4 mmol·L^(-1)of H_(2)O_(2)under irradiation.Investigation results clarify that the calculated position of Fe_(2)O_(3)/TiO_(2)NTs valence band is at 2.944 eV,its potential is higher than the potential of OH~-/·OH(2.800 eV),thereby ensuring the generation of·OH.Meanwhile,the transformation of photogenerated electrons from the conduction band of TiO_(2)to Fe_(2)O_(3)accelerates the reduction of Fe^(3+)to Fe^(2+).The unstable Fe^(2+)can be oxidized by H_(2)O_(2)to produce high yields of·OH.Therefore,both the coaxial heterojunction and fast Fe^(2+)/Fe^(3+)conversion provide abundant·OH to effective attack the electron-deficient benzene ring passivated by the nitro group.Thus,surface-catalyzed degradation of 4-nitrophenol can be carried out step by step.This work contributes a detailed understanding of charge transfer in semiconductor composites and degradation of organic contaminants.

Self-powered electrochemical system by combining Fenton reaction and active chlorine geheration for organic contaminant treatment

Environmental deterioration,especially water pollution,is widely dispersed and could affect the quality of people's life at large.Though the sewage treatment plants are constructed to meet the demands of cities,distributed treatment units are still in request for the supplementary of centralized purification beyond the range of plants.Electrochemical degradation can reduce organic pollution to some degree,but it has to be powered.Triboelectric nanogenerator(TENG)is a newly-invented technology for low-frequency mechanical energy harvesting.Here,by integrating a rotary TENG(R-TENG)as electric power source with an electrochemical cell containing a modified graphite felt cathode for hydrogen peroxide(H2O2)along with hydroxyl radical(·OH)generation by Fenton reaction and a platinum sheet anode for active chlorine generation,a self-powered electrochemical system(SPECS)was constructed.Under the driven of mechanical energy or wind flow,such SPECS can efficiently degrade dyes after power management in neutral condition without any O2 aeration.This work not only provides a guideline for optimizing self-powered electrochemical reaction,but also displays a strategy based on the conversion from distributed mechanical energy to chemical energy for environmental remediation.

Sustainable wood-based nanotechnologies for photocatalytic degradation of organic contaminants in aquatic environment

Wood-based nanotechnologies have received much attention in the area of photocatalytic degradation of organic contaminants in aquatic environment in recent years,because of the high abundance and renewability of wood as well as the high reaction activity and unique structural features of these materials.Herein,we present a comprehensive review of the current research activities centering on the development of wood-based nanocatalysts for photodegradation of organic pollutants.This review begins with a brief introduction of the development of photocatalysts and hierarchical structure of wood.The review then focuses on strategies of designing novel photocatalysts based on wood or its recombinants(such as 1D fiber,2D films and 3D porous gels)using advanced nanotechnology including sol-gel method,hydrothermal method,magnetron sputtering method,dipping method and so on.Next,we highlight typical approaches that improve the photocatalytic property,including metal element doping,morphology control and semiconductor coupling.Also,the structure-activity relationship of photocatalysts is emphasized.Finally,a brief summary and prospect of wood-derived photocatalysts is provided.

Hierarchical porous metal-organic frameworks/polymer microparticles for enhanced catalytic degradation of organic contaminants

This work reports on a simple microfluidic strategy to controllably fabricate uniform polymeric microparticles containing hierarchical porous structures integrated with highly accessible catalytic metal organic frameworks for efficient degradation of organic contaminants.Monodisperse(W1/O)/W2 emulsion droplets generated from microfluidics are used as templates for the microparticle synthesis.The emulsion droplets contain tiny water microdroplets from homogenization and water nanodroplets from diffusion-induced swollen micelles as the dual pore-forming templates,and Fe-based metal-organic framework nanorods as the nanocatalysts.The obtained microparticles possess interconnected hierarchical porous structures decorated with highly accessible Fe-based metal-organic framework nanorods for enhanced degradation of organic contaminants via a heterogeneous Fenton-like reaction.Such a degradation performance is highlighted by using these microparticles for efficient degradation of rhodamine B in hydrogen peroxide solution.This work provides a simple and general strategy to flexibly combine hierarchical porous structures and catalytic metal-organic frameworks to engineer advanced microparticles for water decontamination.

Efficient elimination of organic contaminants with novel and stable zeolite@MOF layer adsorbents

Many metal-organic frameworks(MOFs)trapped in water exhibit instability and small-particle agglomeration issues,which unquestionably constrain their potential applications,such as the capture of organic contaminants(OCs).In this study,four types of micron-sized MOFs(Zn/Cu-BTC,MOF-5,ZIF-8,and UiO-66)were grown within a zeolite-13X support to form millimeter-sized zeolite-13X@MOF composites for the elimination of benzothiophene,methyl orange,and tetracycline from the liquid phase by dynamic adsorption in a column.We observed that the 13X@Zn/Cu-BTC exhibited extraordinarily high OC capture capacities as a result of the Zn^(2+) and Cu^(2+) combinative effects of the acid-base interaction.Remarkably,the 13X@UiO-66 preserved its structural integrity when immersed in water for 15 days,in contact with boiling water for 12 h,and in both strong acidic and basic aqueous media.Moreover,the OC capture abilities of the 13X@UiO-66 only underwent a slight change after the fifth round.This work provides new method for the design of desirable millimeter-sized zeolite@MOFs,thereby advancing their practical application for OC capture.

Complex interplay between formation routes and natural organic matter modification controls capabilities of C_(60)nanoparticles(nC_(60)) to accumulate organic contaminants

Accumulation of organic contaminants on fullerene nanoparticles（nC（60）） may significantly affect the risks of C（60） in the environment.The objective of this study was to further understand how the interplay of nC（60） formation routes and humic acid modification affects contaminant adsorption of nC（60）.Specifically,adsorption of 1,2,4,5-tetrachlorobenzene（a model nonionic,hydrophobic organic contaminant） on nC（60） was greatly affected by nC（60）formation route- the formation route significantly affected the aggregation properties of nC（60）,thus affecting the available surface area and the extent of adsorption via the pore-filling mechanism.Depending on whether nC（60） was formed via the ＂top-down＂ route（i.e.,sonicating C（60） powder in aqueous solution） or ＂bottom-up＂ route（i.e.,phase transfer from an organic solvent） and the type of solvent involved（toluene versus tetrahydrofuran）,modification of nC（60） with Suwannee River humic acid（SRHA） could either enhance or inhibit the adsorption affinity of nC（60）.The net effect depended on the specific way in which SRHA interacted with C（60） monomers and/or C（60） aggregates of different sizes and morphology,which determined the relative importance of enhanced adsorption from SRHA modification via preventing C（60） aggregation and inhibited adsorption through blocking available adsorption sites.The findings further demonstrate the complex mechanisms controlling interactions between nC（60） and organic contaminants,and may have significant implications for the life-cycle analysis and risk assessment of C（60）.

Construction of MoFs-based nanocomposite membranes for emerging organic contaminants abatement in water

Presence of emerging organic contaminants(EOCs)in water is one of the major threats to water safety.In recent decades,an increasing number of studies have investigated new approaches for their effective removal.Among them,metal-organic frameworks(MOFs)have_attracted increasing attention since their first development thanks to their tunable metal nodes and versatile,functional linkers.However,whether or not MOFs have a promising future for practical application in emerging contaminants-containing wastewater is debatabie.This review summarizes recent studies about the removal of EOCs using MOFs-related material.The synthesis strategies of both MOF particles and composites,including thin-film nanocomposite and mixed matrix membranes,are criticaily reviewed,as well as various characterization technologies.The application of the MOF-based composite membranes in adsorption,separation(nanofiltration and ultrafiltration),and catalytic degradation are discussed.Overall,literature survey shows that MOFs-based composite could play a crucial role in eliminating EOCs in the future.In particular,modified membranes that realize separation and degradation might be the most promising materials for such application.

Enhanced utilization efficiency of peroxymonosulfate via water vortex-driven piezo-activation for removing organic contaminants from water

The efficient activation and utilization of peroxymonosulfate(PMS)in PMS-based advanced oxidation processes is a high-priority target for the removal of organic contaminants.This work introduces a water vortex-driven piezoelectric effect from few-odd-layered MoS_(2)into the PMS activation to remove benzotriazole(BTR)and other organic contaminants from the water.Approximately 91.1%of BTR can be removed by the MoS_(2)piezo-activated PMS process with a reaction rate constant of 0.428 min
1,which is 2.09 times faster than the sum of the individual MoS_(2),water vortex,and piezocatalysis rates.Meanwhile,the PMS utilization efficiency reached 0.0147 in the water vortex-driven piezo-activation system,which is 3.97 times that of the sum from the vortex/PMS and MoS_(2)/PMS systems.These results demonstrate that the presence of MoS_(2)under a water vortex can trigger a piezoelectric potential and generate abundant free electrons to activate PMS to generate various active species for degradation of organic contaminants.

Peroxymonosulfate enhanced photoelectrocatalytic oxidation of organic contaminants and simultaneously cathodic recycling of silver

Degradation of organic contaminants with simultaneous recycling of Ag+from silvercontaining organic wastewater such as photographic effluents is desired. Although photoelectrocatalysis(PEC) technology is a good candidate for this type of wastewater, its reaction kinetics still needs to be improved. Herein, peroxymonosulfate(PMS) was employed to enhance the PEC kinetics for oxidation of phenol(PhOH) at the anode and reduction of Ag^(+) at the cathode. The degradation efficiency of phenol(PhOH, 0.1 mmol/L) was increased from 42.8% to 96.9% by adding 5 mmol/L PMS at a potential of 0.25 V. Meanwhile, the Ag(by wt%)deposited on the cathode was 28.1%(Ag_(2)O) in PEC process, while that of Ag(by wt%) was 69.7%(Ag^(0)) by adding PMS. According to the electrochemistry analysis, PMS, as photoelectrons acceptor, enhances the separation efficiency of charges and the direct hoxidation of Ph OH at the photoanode. Meantime, the increasing cathode potential avoided Hevolution and strongly alkaline at the surface of cathode, thus enabling the deposition of Ag+in the form of metallic silver with the help of PMS. In addition, PMS combined with PEC process was effective in treating photographic effluents.