Refractory Organic Substances Research Articles

H2O2 oxidation – CaO precipitation pretreatment combining forward osmosis for electroless nickel spent tank liquid (ENSTL) reduction

ABSTRACT The electroless nickel spent tank liquid (ENSTL), as a typical hazardous waste, contains a variety of refractory organic substances as well as heavy metals and inorganic salts. Generally, ENSTL is delegated for disposing by qualified hazardous waste disposal departments in China. However, the temporary storage, transportation, and higher entrusted disposal expenses increase the burden on enterprises producing the hazardous ENSTL. This paper explored an oxidation/precipitation pretreatment and forward osmosis (FO) combined process for ENSTL reduction. 400 mmol/L Hydrogen peroxide and 5.0 wt% calcium oxide were selected as the optimal pretreatment in order to minimize the osmotic pressure of ENSTL, by which the conductivity was significantly reduced from 50.8 mS/cm to 26.8 mS/cm. As a result, the concentrating factor (N) could be dramatically increased from 2.45 by the direct FO to 8.71 by the combined system. Accordingly, the average water flux during the 24 h concentrating cycle increased from 2.47 L/(m2·h) to 4.56 L/(m2·h). TOC rejection rate decreased from 90.23% to 84.39% due to the transformation of organic matter forms by the chemical oxidation during the pretreatment. Meanwhile, TP, Ni and NH4 + rejection rates decreased to a certain extent, which may related to the mitigation of membrane fouling by the pretreatment.

Optimizing bimetallic-insect exuviate melanin composite cathodes using response surface methodology to enhance the H2O2 yield and selectivity of the electro-Fenton process

Electro-Fenton is a fast and efficient oxidative degradation technology for treating many refractory organic substances. However, the poor electrochemical performance and power generation capacity of the cathode during electro-Fenton treatment limit H2O2 generation and pollutant removal. A FeCu bimetal–melanin cathode catalyst with high H2O2 production, low Fe3+ formation, and low resistance was optimized using response surface methodology. The composite desirability coefficient was as high as 0.9281, indicating that the two-factor setting conditions yielded the optimal response results. The synergistic effect between Fe and Cu and the ionic conductivity of melanin promote the conversion between Fe2+ and Fe3+ and improve the charge transfer ability of the cathode. The optimized Fe–Cu–Me cathodic catalyst had the highest H2O2 generation (217.91 ± 4.65 mg/L) and the lowest resistance value (190.33 Ω), 4.88 times and 5.05 % that of the unmodified cathode, respectively; also the lowest Fe3+ generation was 32 % and 73 % that of the Fe and FeCu cathodic catalysts, respectively. Moreover, the optimized Fe–Cu–Me cathode catalyst exhibited up to 80 % selectivity for 2-electron oxygen reduction reaction-catalyzed H2O2 generation based and excellent O2 and H2O2 adsorption performance on ring disk electrode analysis and density function theory calculation. This study is the first to use FeCu bimetals combined with insect exuviate melanin as a cathode catalyst for the in situ generation of cathodic H2O2. The high performance and stability of the fabricated electrocatalyst can be used in the subsequent treatment of wastewater through the electro-Fenton process, providing an innovative approach to improve the performance of the cathode.

Treatment of membrane-concentrated landfill leachate by heterogeneous chemical and electrical Fenton processes with Iron-loaded granular activated carbon catalysts

The composition of the membrane-concentrated landfill leachate (MCLL) is complex with a high concentration of organic matter and inorganic ions. In this study, a chemical and an electro-Fenton system were constructed to treat MCLL from a mature landfill using granular activated carbon loaded with iron oxides as heterogeneous Fenton catalysts. In the chemical Fenton treatment optimized by orthogonal experiments, the COD and colour removal rates were 93.9% and 80.2%. For the electro-Fenton system, the best COD, colour, and TN removal rates of MCLL reached 95.7%, 99%, and 94.9% with an energy consumption (EC) of 0.098 kWh·(g COD)−1 under the condition of pH 6, applied voltage 8 V, the reaction time 4 h, and the catalyst dosage 16.67 g L−1. Various spectral analyses confirmed that refractory organic matter and toxic substances in the MCLL were effectively degraded. The synergistic effect study of the factors in chemical Fenton indicated that as far as the effect on COD removal is concerned, heterogeneous Fenton system > catalyst adsorption > activated carbon/H2O2 system > activated carbon adsorption. The results of free radical quenching experiments illustrate that a large amount of ·OH was produced in the chemical heterogeneous Fenton system, while both ·OH and active chlorine play important roles in the removal of pollutants for the electro-Fenton system. MCLL can be disposed of costly and effectively by chemical and electrical Fenton processes with Iron-loaded granular activated carbon catalysts.

Synergistic photocatalytic ozonation of eliminating chloramphenicol over a 2D MXene-derived heterojunction

Herein, we demonstrate the first example of applying 2D MXene hetero-interfaced nanocomposites for a photocatalytic ozonation of chloramphenicol (CAP). The hierarchical 2D/2D Bi2MoO6/Ti3C2Tx MXene (BMT) hybrid enables a high CAP removal ratio of 95 % within 60 min that outperforms bare Bi2MoO6. Evidences from theoretical calculations and experimental findings prove that the adsorption capability of O3/O2 onto BMT surfaces is elevated and the electron transfer process is accelerated by virtue of hybridization with Ti3C2Tx, thus facilitating the generation of reactive oxygen species (ROSs) including •OH, 1O2 and •O2−. Such elaborate design provides a novel type of robust and cost-effective material adapted for integrated advanced oxidation processes (AOPs) in highly efficient removal of refractory organic substances in water environments.

Removing refractory organic substances from landfill leachate using a nanofiltration membrane bioreactor: Performance and mechanisms

Membrane bioreactors (MBRs) are typically used to dispose landfill leachate, but they are challenged by the low removal of refractory organic substances. To address this challenge, in this study, we replaced the commonly used microfiltration (MF) membranes in conventional MBRs with nanofiltration (NF) membranes, i.e., MBRNF. We operated a one-step MBRNF for 127 days and benchmarked against a conventional MBRMF in terms of membrane fouling, pollutants removal, and bulk solution properties. The results showed that the NF membrane could effectively reject refractory organic substances, leading to a longer organic retention time (ORT) and a higher concentration of refractory organic substances in the bioreactor. Consequently, the MBRNF outperformed MBRMF by 20 %–30 % in removing of refractory organic substances, mainly by the enhanced biodegradation of refractory organic substances with low molecular weight. Further investigation suggested that the enhanced biodegradation in the MBRNF could be ascribed to 1) more biomass in the bioreactor; 2) higher concentration of refractory organic substances in the bioreactor; and 3) the enrichment of dominant bacteria such as Chloroflexi. These findings highlight the potential of MBRNF in removing refractory organic substances from landfill leachate and other wastewaters with poor biodegradability.

Removal of refractory organic matter from landfill-contaminated groundwater by a permeable reactive barrier coupled with an Fe0/PMS advanced oxidation system

Advanced oxidation technology based on peroxymonosulfate (PMS) has attracted much attention because of its good degradation and even mineralization of refractory organic matter, but it is less used in the removal of refractory organic matter from landfill-contaminated groundwater (CGW). In this study, an Fe0/PMS advanced oxidation system-based permeable reactive barrier (Fe0/PMS-PRB) has been employed to remove refractory organic matter from landfill leachate CGW. The results show that the Fe0/PMS system offers a significantly higher removal efficiency of organic matter, especially humus, from CGW than other control systems. The main active oxygen species are SO4•─ and HO•, which can facilitate electron-transfer, carbonylation, electrophilic addition, decarboxylation, and other pathways to effectively degrade various refractory organic substances (e.g., bisphenol A, diclofenac acid, and ciprofloxacin). The pseudo-first-order reaction rates reached 0.1083, 0.3030, and 0.0641 min−1, respectively, effectively reducing the bio-toxicity of the effluent. Based on observations by scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy, a reaction mechanism was proposed, which involves homogeneous oxidation, heterogeneous oxidation, adsorption, and precipitation of Fe0. In long-term seepage tests, under conditions of an Fe0 loading of 0.7 g, a PMS concentration of 0.8 mm, and a hydraulic retention time of 15 min, after running for 10 pore volumes, the removal extents of aromatic organic matter and total organic carbon from the CGW by the Fe0/PMS-PRB reached 79.01 % and 68.25 %, respectively. Therefore, Fe0/PMS-PRB can effectively remove refractory organic matter from CGW and has good application prospects.

Three-dimensional graphene aerogel mitigated the toxic impact of chloramphenicol wastewater on microorganisms in an EGSB reactor

Anaerobic treatment of chloramphenicol wastewater holds significant promise due to its potential for bioenergy generation. However, the high concentration of organic matter and residual toxic substances in the wastewater severely inhibit the activity of microorganisms. In this study, a three-dimensional graphene aerogel (GA), as a conductive material with high specific surface area (114.942 m2 g−1) and pore volume (0.352 cm3 g−1), was synthesized and its role in the efficiency and related mechanism for EGSB reactor to treat chloramphenicol wastewater was verified. The results indicated that synergy effects of GA for Chemical Oxygen Demand (COD) removal (increased by 8.17 %), chloramphenicol (CAP) removal (increased by 4.43 %) and methane production (increased by 70.29 %). Furthermore, GA increased the average particle size of anaerobic granular sludge (AGS) and promoted AGS to secrete more redox active substances. Microbial community analysis revealed that GA increased the relative abundance of functional bacteria and archaea, specifically Syntrophomonas, Geobacter, Methanothrix, and Methanolinea. These microbial species can participate in direct interspecific electron transfer (DIET). This research serves as a theoretical foundation for the application of GA in mitigating the toxic impact of refractory organic substances, such as antibiotics, on microorganisms during anaerobic treatment processes.

Application of Co3O4 in Photoelectrocatalytic Treatment of Wastewater Polluted with Organic Compounds: A Review

The negative effects of refractory organic substances in water on the environment and life have aroused worldwide attention. The efficiency of using photoelectrocatalysis (PEC) to degrade refractory organic pollutants depends to a large extent on the properties of the photoanode semiconductor. Therefore, the selection of a satisfactory photoanode semiconductor material to promote the production of intermediate reactive species (hydroxyl radicals and superoxide radicals) has become a key issue in improving the efficiency of PEC. Among the available catalysts, transition metal oxides have received a lot of attention in recent years due to their low price and significant advantages. Due to its outstanding photoelectrocatalytic properties, Co3O4 has emerged as a candidate to serve as a photoelectrocatalyst specifically for the oxidation of water with oxygen in these materials. This paper summarizes in detail the recent advances in Co3O4 materials for PEC, both pure Co3O4 and Co3O4-based composites. In addition, this review discusses the impact of strategies on the performance of photoelectrocatalysts, such as synthesis methods, crystal surface structures, and composites. Finally, this review concludes with a presentation of the challenges and workable solutions for Co3O4-based materials in PEC, along with a discussion of their potential for future research.

Enhancement of Wastewater Treatment Using Mist and Photocatalyst

AbstractAdvanced oxidation processes are attractive methods for treating wastewater containing refractory organic substances. Hybrid reactors utilizing mist generated by ultrasound and photocatalysts have been proposed to enhance pollutant removal. However, the functions of ultraviolet, ultrasound, mist, and photocatalyst in the hybrid reactor have not been clarified. The aim of this study is to investigate these functions by comparing the pollutant removal performance under different operating conditions. The results indicate that the application of ultraviolet, ultrasound, and photocatalyst is necessary to utilize mist as a reaction field. A synergistic effect of the simultaneous application was observed in the hybrid reactor.

Mussel-Inspired Catechol-Grafted Quaternized Chitosan Flocculant for Efficiently Treating Suspended Particles and Refractory Soluble Organic Pollutants

It remains challenging yet of great importance to develop a qualified biopolymer-derived flocculant in treating complex high-salinity wastewaters polluted by suspended solids and refractory soluble organic substances such as organic dyes. The key to this success is to endow the developed flocculants with versatile intermolecular and interfacial interactions in high salinity to trigger effective flocculation. Herein, inspired by mussel’s powerful wet adhesion in a salted marine environment to diverse interfaces, we develop a mussel-inspired chitosan-based flocculant (CQ-CS) by simultaneously grafting catechol and cationic trimethylammonium groups to chitosan backbones. Compared with its cationic compartment, the optimal dosage of CQ-CS is decreased greatly after introducing catechol groups. Moreover, CQ-CS works in a wide pH range from 2 to 7 and can achieve more than 95% removal efficiency of soluble organic dyes and suspended particles such as anionic dyes and kaolin clay at the optimal dosages. More importantly, the flocculation performance of CQ-CS exhibits excellent tolerance to the salinity. As NaCl concentration increases from 0 to 2000 mg/L, CQ-CS maintained similar removal efficiencies for organic dyes, while the removal efficiency of quaternized chitosan (Q-CS) for organic dyes decreased by approximately 8% at this salinity. Finally, CQ-CS exhibits excellent flocculation performance to industrial dyeing wastewaters.

Comparative study on the treatment of refractory organics in landfill leachate by homogeneous and heterogeneous Fenton advanced oxidation processes.

With the advancement of the landfill stabilization process of municipal solid waste, landfill leachate containing a large amount of refractory organic matter is formed. In this study, homogeneous Fenton and heterogeneous Fenton-like (activation by zero valent iron (Fe0), pyrite (FeS2) and magnetite (Fe3O4) as solid iron materials) processes have been compared for the removal of refractory organics from landfill leachate. The removal efficiency of organics in the Fenton process was slightly higher than those in the Fenton-like processes. The removal efficiencies based on total organic carbon, UV absorbance at 254 nm (UV254) and colour number in the Fenton process were as high as 57.42%, 71.63% and 81.03%, respectively. In the Fenton-like processes, the Fe0/H2O2 process achieved 35.74%, 66.24% and 86.29% removal efficiencies, respectively. Moreover, the degradation effect on refractory organic substances proved to be better. In the Fenton-like processes, the activation mechanisms with Fe0 and FeS2 involve the homogeneous activation of Fe2+ in solution and heterogeneous activation of iron oxides produced during the reaction, respectively. With Fe3O4, the activation mechanism is mainly a heterogeneous process involving its intrinsic iron oxide constituents. This study may provide a theoretical basis for the treatment of refractory organics in landfill leachate.

Combination of coagulation, Fe0/H2O2 and ultra-high lime aluminium processes for the treatment of residual pollutants in biologically-treated landfill leachate

ABSTRACT Refractory substances (humus) and salts (chloride (Cl−) and sulphate (SO4 2−) ions) remain in the biotreated landfill leachate treatment, and it is necessary to carry out further treatments by a suitable method before discharge. In this study, the effect and operational mechanism of a combination of the coagulation Fe0/H2O2 and ultra-high lime aluminium (UHLA) processes for the treatment of refractory organic substances and salts in the leachate effluent of a semi-aerobic aged refuse biofilter (SAARB) were investigated. The results showed that polyferric sulphate is a relatively efficient coagulant comparing to FeCl3, Al2(SO)4, and polyaluminium chloride. The Fe0/H2O2 process further removed refractory organics from wastewater, achieving 49.8% of total organic carbon removed. Further treatment by the UHLA process was carried. The results demonstrated that the amount of precipitant, reaction duration, and temperature had a significant impact on the Cl− and SO4 2− removals. After three treatments, the cumulative SO4 2− and Cl− removal efficiencies were 98% and 80%, respectively. The SO4 2− and Cl− were removed in the form of precipitates such as UHLA, specific components of which included calcium alumina, Fremy's salt of calcium, aluminium chloride, and calcium hydroxide. Overall, the UV254, CN, Cl−, and SO4 2− removal efficiencies from the SAARB effluent were 94.08%, 98.73%, 79.96%, and 98.44%, respectively, for the combined coagulation Fe0/H2O2 and UHLA processes. Therefore, the combined processes could effectively remove residual pollutants in the biologically-treated landfill leachate, and the study provides a useful reference for the removal of refractory organic matter and salts in landfill leachate. Highlights Coagulation-Fe0/H2O2-UHLA process is effective to SAARB effluent treatment. Refractory organics are substantially degraded by the coagulation-Fenton-like stage. Both Cl− and SO4 2− in SAARB effluent are greatly removed by UHLA process.

Volume reduction and water reclamation of reverse osmosis concentrate from coal chemical industry by forward osmosis with an osmotic backwash strategy.

Coal chemical industry (CCI) generally utilizes reverse osmosis (RO) for water reclamation, which generates a highly concentrated stream containing refractory organic substances and high-concentration total dissolved solids (TDS). To address this issue, the present work focuses on volume reduction of RO concentrate (ROC) produced from CCI by forward osmosis (FO). We investigated the effects of membrane orientation and draw solution (DS) concentration on FO performance. Foulant removal was tested by using chemical cleaning, physical cleaning and osmotic backwash (OB). AL-FS (active layer facing feed solution) mode outcompeted AL-DS (active layer facing draw solution) mode, achieving a flux of 26.4 LMH, 92.5% water reclamation and energy consumption of 0.050 kWh·m-3 with 4 M NaCl as DS. The FO process was able to reject >98% SO4 2-, Mg2+and Ca2+, 92-98% Si and 33-55% total organic carbon (TOC). Ten-cycle (10 × 20 h) accelerated fouling test demonstrated approximately 30% flux decline in association with Si-containing foulants, which could be removed almost completely through OB with 97.1% flux recovery. This study provides a proof-of-concept demonstration of FO for volume reduction and water reclamation of ROC produced from CCI, making the treatment of ROC more efficient and more energy effective.

Different refractory organic substances degradation and microbial community shift in the single-chamber bio-photoelectrochemical system

The single-chamber bio-photoelectrochemical system (BPES) with a BiOBr photocathode was developed for acid orange 7 (AO7), 2,4 dichlorophenol (2,4-DCP) and chloramphenicol (CAP) degradation under solar irradiation. Photoelectrochemical characterizations showed that the optimized BiOBr-photocathode exhibited great light-response property and excellent electrochemcial performance. Moreover, desired TOC removals were achieved for various organic pollutants, with the values of 90.97% (AO7), 81.41% (2,4-DCP) and 78.47% (CAP). Besides, the lower cathode potentials in the illuminated BPESs were favorable to efficient pollutants degradation. Significant microbial community shifts were observed among the inoculation and anodic biofilms from the BPES, and the most dominated species in anodic biofilms acclimated to various pollutants were Geobacter and Pseudomonas, which have the abilities of extracellular electrons transfer and organics degradation. Some other species that different from the inoculation were also identified from the BPES biofilms. This study suggested that BPES had great potential for refractory organics degradation.

Impacts of advanced treatment processes on elimination of antibiotic resistance genes in a municipal wastewater treatment plant

Antibiotic resistance genes (ARGs) pose a serious threat to public health. Wastewater treatment plants (WWTPs) are essential for controlling the release of ARGs into the environment. This study investigated ARG distribution at every step in the treatment process of a municipal WWTP located in Harbin for six consecutive months. Changes in ARG distribution involved in two advanced secondary effluent treatment processes, ozonation and granular activated carbon (GAC) adsorption, were analyzed. Biological treatment resulted in the highest ARG removal (0.76–1.94 log reduction), followed by ultraviolet (UV) disinfection (less than 0.5-log reduction). Primary treatment could not significantly remove ARGs. ARG removal efficiency increased with an increase in the ozone dose below 40 mg/L. However, amorphous GAC (AGAC) adsorption with a hydraulic retention time (HRT) of 1 h showed better removal of ARGs, total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) than ozonation at a 60 mg/L dose. UV treatment could efficiently reduce the relative ARG abundance, despite presenting the lowest efficiency for the reduction of absolute ARG abundance compared with GAC and ozone treatments. The combination of ozone and AGAC can significantly improve the removal of ARGs, TOC, TN and TP. These results indicate that a treatment including biological processing, ozonation, and AGAC adsorption is a promising strategy for removing ARGs and refractory organic substances from sewage.

Options for Removing Refractory Organic Substances in Pre-Treated Process Water from Hydrothermal Carbonization

Granular activated carbon (GAC) adsorption, as well as ozonation in combination with biodegradation was investigated in order to remove refractory organics from biologically pre-treated process waters (PW) produced by the hydrothermal carbonization (HTC) of spent grains and fine mulch. Kinetic tests revealed that the organics in spent grains PW had much lower molecular weights than organics in fine mulch PW. Moreover, isotherms showed that they were more strongly adsorbable. This was confirmed in GAC column experiments, where the breakthrough curves could be predicted fairly well by a dynamic adsorption model. On the other hand, ozonation had a stronger effect on fine mulch PW with respect to an enhancement of the aerobic degradability. Thus, the type of input material determines the properties of soluble reaction products from the carbonization process that must be accounted for when selecting the most suitable post-treatment method for HTC PW. However, adsorption on granular activated carbon should always be the final stage.

Visible-light-driven photocatalytic activity of mixed phase CdS-flakes

A mixed phase cadmium sulfide (CdS) thin films were prepared through chemical synthesis for studying the visible-light-driven photocatalytic activity for wastewater treatment. The wastewater that contains a considerable amount of refractory organic substances such as congo red (CR), methylene blue (MB) and indigo carmine (IC) dye solutions were degraded under visible-light irradiation using the CdS thin films. Structural studies of the CdS photocatalyst indicated good crystallinity, showing mixed phases of the hexagonal and cubic structure. Morphological studies suggested a flake-like structure that is uniformly distributed over the entire surface of the substrate. Such morphology induces porosity, which helps for intercalating the organic dyes. The optical band-gap energy of film sample was found to be 2.35 eV, which helped for high photocatalytic activity in the degradation of the non-biodegradable CR dye under visible-light irradiations as compared to IC and MB dyes.

Using combined multiple techniques to characterize refractory organics during anammox process with mature coal chemical wastewater as influent.

This study combined spectroscopy techniques to assess the composition of refractory organics and highlighted the potential application of excitation-emission matrix (EEM) fluorescence spectroscopy within future monitoring of coal chemical wastewater treatment by the anammox process. The results showed that the anammox process could effectively degrade refractory organic substances, with fulvic-like, UV-humic acid, and Vis-humic acid component removal efficiencies of 43.61, 53.93, and 100%, respectively. In this study, EEM fluorescence spectroscopy was proven to be an effective method of assessing the removal of dissolved organic nitrogen during anammox treatment of mature coal chemical wastewater. Furthermore, remarkable accumulation (9.3-16.2%) of Ca. Kuenenia occurred in the anammox granules that underwent long-term cultivation in mature coal chemical wastewater, which provided the high nitrogen removal rate. The abundance of Anaerolineaceae and Bacteroides was vital in refractory organic degradation.

Characterisation of transparent exopolymer particles (TEP) produced during algal bloom: a membrane treatment perspective

Algal blooms are currently a major concern of the membrane industry as it generates massive concentrations of organic matter (e.g. transparent exopolymer particles [TEP]), which can adversely affect the operation of membrane filtration systems. The goal of this study is to understand the production, composition and membrane rejection of these organic materials using different characterisation techniques. Two common species of bloom-forming freshwater and marine algae were cultivated in batch cultures for 30 days and the productions of TEP and other organic matter were monitored at different growth phases. TEP production of the marine diatom, Chaetoceros affinis, produced 6–9 times more TEP than the freshwater blue-green algae, Microcystis. The organic substances produced by both algal species were dominated by biopolymeric substances such as polysaccharides (45–64%) and proteins (2–17%) while the remaining fraction comprises of low molecular weight refractory (humic-like) and/or biogenic organic substances. MF/UF membranes mainly rejected the biopolymers but not the low molecular weight organic materials. MF membranes (0.1–0.4 μm) rejected 42–56% of biopolymers, while UF membranes (10–100 kDa) rejected 65–95% of these materials. Further analysis of rejected organic materials on the surface of the membranes revealed that polysaccharides and proteins are likely responsible for the fouling of MF/UF systems during an algal bloom situation.

Research on Synergistic Effect of Microwave Irradiation-Fenton Oxidation Coupling Coagulation Process to Treat Dye Wastewater

From various aspects, enhancement effect of microwave and synergistic effect of the combined process were investigated systematically to treat dye wastewater using microwave irradiation-Fenton oxidation coupling coagulation process. The results showed when microwave was introduced to enhance Fenton oxidation and coagulation process, the degradation efficiency of refractory organic substances in dye wastewater was significantly promoted, and treatment time and various dosages of flocculant, oxidant and catalyzer were also reduced obviously. The synergistic effect discussion of the combined system also indicated that microwave irradiation brought not only the thermal efficiency but also the non-thermal efficiency, which would accelerate to produce more hydroxyl radicals, and promote the molecular polarization of organic substances. The physical and chemical properties of refractory organic substances in dye wastewater could be changed, which would be helpful for the follow-up Fenton oxidation and coagulation process. These facts fully embodied that there existed synergetic effects in microwave irradiation-Fenton oxidation coupling coagulation process.