Organic Wastewater Treatment Research Articles

Salt stress altered anaerobic microbial community and carbon metabolism characteristics: The trade-off between methanogenesis and chain elongation

Discharge of saline organic wastewater is increasing worldwide, yet how salt stress disrupts the microbial community's structure and metabolism in bioreactors has not been systematically investigated. The non-adapted anaerobic granular sludge was inoculated into wastewater with varying salt concentration (ranging from 0% to 5%) to examine the effects of salt stress on the structure and function of the anaerobic microbial community. Result indicated that salt stress had a significant impact on the metabolic function and community structure of the anaerobic granular sludge. Specifically, we observed a notable reduction in methane production in response to all salt stress treatments (r = −0.97, p < 0.01), while an unexpected increase in butyrate production (r = 0.91, p < 0.01) under moderate salt stress (1–3%) with ethanol and acetate as carbon sources. In addition, analysis of microbiome structures and networks demonstrated that as the degree of salt stress increased, the networks exhibited lower connectance and increased compartmentalization. The abundance of interaction partners (methanogenic archaea and syntrophic bacteria) decreased under salt stress. In contrast, the abundance of chain elongation bacteria, specifically Clostridium kluyveri, increased under moderate salt stress (1–3%). As a consequence, the microbial carbon metabolism patterns shifted from cooperative mode (methanogenesis) to independent mode (carbon chain elongation) under moderate salt stress. This study provides evidence that salt stress altered the anaerobic microbial community and carbon metabolism characteristics, and suggests potential guidance for steering the microbiota to promote resource conversion in saline organic wastewater treatment.

Expandable polystyrene waste modified iron sludge-based biochar activating multiple free radicals for deep wastewater treatment

Fe-containing sludge can be converted to functional biochar as a promising resource recycle pathway. However, activating properties of Fe sludge-based biochar are always limited by low specific surface area and weak carbon center for persistent free radical(PFRs). In the current study, waste expandable polystyrene particles were simultaneously used to improve the biochar catalytic performance. The co-prepared biochar achieved a high micromesoporous ratio(98.4%) with specific surface area (345.3 m²/g), improved by 20.1% and 105.2% than unimproved biochar. The improved micromesoporous properties performed better iron active sites and oxygen-containing functional groups for PFRs functioning in wastewater. The co-prepared biochar showed an efficient catalytic degradation through persulfate activating multiple free radicals of 1O2, O2˙ˉ, ˙OH and SO4˙ˉ, which removed 95.4% sulfamethoxazole with mineralizing ratio of 74% within 60 min. The recycling of waste iron sludge and waste polystyrene foam material can achieve functional biochar to apply in deep treatment of refractory organic wastewater.

Efficient electrochemical wastewater treatment on a customized three-phase interface

The development of high-performance catalysts for organic wastewater treatment has proven itself to be a very challenging chemical problem. In this issue of Chem Catalysis, Zhang and co-workers report a Ru-MnO2-mTi anode material through a three-phase interface engineering strategy. The Ru-MnO2-mTi catalyst demonstrates exceptional efficiency for the electrochlorination degradation of dyes found in wastewater from the textile industry.

Pilot-scale study and biochemical verification of salt-tolerant catalyst Fe-Bi@γ-Al2O3 for catalytic ozonation of high-salinity wastewater

In this study, Fe-Bi@ γ-Al2O3 was used as a catalyst to construct a heterogeneous catalytic ozonation system for the treatment of high-salinity organic wastewater and its biochemical verification was studied. The optimum operating conditions and degradation mechanism of Fe-Bi@ γ-Al2O3 catalytic ozonation of high salinity wastewater were systematically investigated. The biodegradability of wastewater before and after treatment was also studied. Under the optimum operating conditions of ozone dosage of 160 mg/L, catalyst filling rate of 15%, ratio of height to diameter of 15, hydraulic retention time of 210 min and recycle ratio of 500%, the removal rate of COD is 45.13%. The mechanical strength of Fe-Bi@ γ-Al2O3 catalyst is almost unchanged after being reused for 20 times. The results of Ultraviolet and visible spectrophotometry (UV-Vis), 3D (Three-Dimensional)-fluorescence and Gas Chromatography-Mass Spectrometer (GC-MS)showed that humus, fulvic acid and undissolved microbial organic matter were degraded. In the biochemical verification experiment, after the high salinity wastewater was used to impact the bio-reactor, the mixed liquor suspended solids (MLSS) was basically stable at 9597 mg/L, 8856 mg/L, 9414 mg/L and 8741 mg/L, and the mixed liquor volatile suspended solids (MLVSS) was basically stable at 7042 mg/L, 6940 mg/L, 6949 mg/L and 6519 mg/L. The dissolved oxygen (DO) in the four reactors were 2.9 mg/L, 3.48 mg/L, 3.6 mg/L and 2.92 mg/L respectively, and the sludge Volume Index (SVI30) were 93 mL/g, 98 mL/g, 93 mL/g and 91 mL/g respectively. After two cycles (20d) of 30% high salinity wastewater, the chemical oxygen demand (COD) removal rates of the four reactors were 78%, 84%, 86% and 91%, respectively. When the reaction time is 40 min, the BOD5/COD (B/C) value of the high-salinity wastewater reaches 0.91, and the biodegradability of the wastewater is improved significantly. Scanning electron microscope (SEM) showed that the granular sludge in the reactor had compact structure and smooth surface, and there were a lot of fungi and filamentous microorganisms on the sludge surface.in that condition of salinity stress, the microbial community in the activate sludge changed to a great extent, and Proteobacteria and Bacteroidetes became the main phylum. The Fe-Bi@ γγ-Al2O3 catalyst has good catalytic performance and can be used for deep treatment of high-salt organic wastewater.

A new insight into the generation of hydrogen peroxide from carmine degradation by cryptomelane as a catalyst, oxidant, and adsorbent

Carmine, as a widely used dye, is one kind of refractory organic pollutants that endanger the water environment. Finding an efficient and environmentally friendly degradation method is a crucial step to treat dye-containing wastewater. Using a one-step hydrothermal synthetic method, cryptomelane was synthesized, characterized, and investigated for its ability to degrade carmine in an aqueous solution. Under the optimum conditions of a 2 g/L cryptomelane dosage and an initial pH of 6.8, 97.87% of 100 mg/L carmine degraded within 240 mins. Cryptomelane exhibited excellent reusability after three cycles, with a decolorization efficiency of 85.39%. Cryptomelane accommodated a board working pH range. The carmine was efficiently decolorized via an interaction of oxidation, catalysis, and adsorption of cryptomelane in a ratio of 46.85:47.11:3.90, respectively. The existence of oxygen vacancies on cryptomelane was responsible for H2O2 generation, and O2•- and 1O2 active species were involved in the carmine degradation by cryptomelane. A low reaction activation energy (Ea = 6.36 kJ/mol) caused efficient removal of carmine by cryptomelane at ambient temperature. These findings notably distinguish three roles of cryptomelane as an adsorbent, oxidant, and catalyst in a pollutant removal system, and prove that cryptomelane may have extensive and promising utilization on refractory organic wastewater treatment without the need to add extra oxidants.

Removal of chemical oxygen demand and ammonia nitrogen from high salinity tungsten smelting wastewater by one-step electrochemical oxidation: From bench-scale test, pilot-scale test, to industrial test

In recent years, electrochemical oxidation (EO) shows the characteristics of green and high efficiency in removing chemical oxygen demand (COD) and ammonia nitrogen (NH3–N) from wastewater, which has been favored by researchers. However, at present, most of current studies on EO remain in laboratory stage, reports about pilot-scale or even industrial tests with large treatment capacity are few, which slowing down the use of the advanced technology to practical application. In this study, bench-scale tests, pilot-scale tests (treatment capacity 200–500 L/h), and industrial tests (treatment capacity 100 m3/h) were carried out by EO technology in view of the characteristics of tungsten smelting wastewater (TSW) with high salinity (NaCl), COD, and NH3–N. Results showed that the removal of COD and NH3–N was a competitive reaction in the EO process, and COD could be removed more preferentially than NH3–N. When NH3–N content was low, the influent pH had a minimal effect on its removal, and when NH3–N content was high, increasing the influent pH was beneficial to its removal. Industrial tests showed that the one-step removal of COD and NH3–N in TSW met the standard, and the power consumption per cubic meter of wastewater was only 4.2 kW h, and the treatment cost was much lower than the two-step process of “breaking point chlorination to remove NH3–N and adding oxidant to remove COD”. This study has successfully realized industrial application of EO technology in TSW treatment for the first time and provided a successful case, which is helpful to accelerate the popularization and application of this technology in the field of high salinity organic ammonia nitrogen wastewater treatment.

Application of Photocatalysis and Sonocatalysis for Treatment of Organic Dye Wastewater and the Synergistic Effect of Ultrasound and Light.

Organic dyes play vital roles in the textile industry, while the discharge of organic dye wastewater in the production and utilization of dyes has caused significant damage to the aquatic ecosystem. This review aims to summarize the mechanisms of photocatalysis, sonocatalysis, and sonophotocatalysis in the treatment of organic dye wastewater and the recent advances in catalyst development, with a focus on the synergistic effect of ultrasound and light in the catalytic degradation of organic dyes. The performance of TiO2-based catalysts for organic dye degradation in photocatalytic, sonocatalytic, and sonophotocatalytic systems is compared. With significant synergistic effect of ultrasound and light, sonophotocatalysis generally performs much better than sonocatalysis or photocatalysis alone in pollutant degradation, yet it has a much higher energy requirement. Future research directions are proposed to expand the fundamental knowledge on the sonophotocatalysis process and to enhance its practical application in degrading organic dyes in wastewater.

Unraveling the Roles of MW/UV/TiO2 Photocatalysis Technologies for Organic Wastewater Treatment

Microwave-induced oxidation and UV/TiO2 photocatalytic technologies are widely used for organic wastewater treatment. Furthermore, the combination of these technologies (MW/UV/TiO2) result in a new advanced oxidation process. As a green and efficient photocatalytic degradation technology, MW/UV/TiO2 is favored for its advantages of high removal rate, short time use, wide concentration range, low cost, good stability, and no secondary pollution. Herein, this paper has summarized insights into the removal process by unveiling the degradation mechanism of organic compounds with MW-assisted technology. Additionally, water quality factors and process parameters affect the photocatalytic efficiencies, consisting of initial concentration, initial volume, TiO2 dosage, UV intensity, microwave power, temperature, pH, and fluid velocity, which have been systematically analyzed. Finally, possible future research directions and guidelines are proposed. Our findings will provide a way forward for the development of effective microwave-assisted remediation technologies that are broadly applicable to various environmental contamination scenarios.

Treatment of bisphenol pollutant in water by N,P-co-doped carbon nanosheet: Fast degradation, toxicity elimination and reaction mechanism investigation

Metal-free carbon catalysts perform well in peroxymonosulfate-based advanced oxidation process for the treatment of organic pollutant-containing wastewater. Herein, a natural biomolecule of adenosine triphosphate (ATP), containing abundant N and P elements, served as sole precursor to prepare N,P-co-doped carbon through one-step anoxic pyrolysis, which was applied as peroxymonosulfate activator to treat bisphenol-contaminated water. Owing to the endogenous N and P elements in ATP, in-situ doping was achieved for the prepared carbon material with excellent doping effect, such as high doping amount and numerous defects. During pyrolysis process, the generated gases facilitated the exfoliation of carbon structure, resulting in a nanosheet-like morphology with large specific surface area, e.g., 852.75 m2 g−1 for NPCN-900 sample obtained at 900 °C. Benefiting from the structural modulation brought by N,P co-doping, typical sample of NPCN-900 presented excellent catalytic performance towards bisphenol AF (BPAF) degradation through PMS activation. An apparent reaction rate constant of 0.4115 min−1 was calculated under the investigated reaction conditions. Further studies indicated that 1O2, surface-bound •OH and SO4−• worked together in NPCN-900/PMS system for BPAF degradation. Graphitic N, pyrrolic N, CO groups, defect structure and the doped P atoms in NPCN-900 contributed to PMS activation. It was also important that the toxicity of BPAF solution could be preliminarily eliminated after treatment by NPCN-900/PMS system, which was verified by ecotoxicity assessments through ECOSAR program and green algae growth experiments.

Potential of direct granulation and organic loading rate tolerance of aerobic granular sludge in ultra-hypersaline environment

Salt-tolerant aerobic granular sludge (SAGS) technology has shown potentials in the treatment of ultra-hypersaline high-strength organic wastewater. However, the long granulation period and salt-tolerance acclimation period are still bottlenecks that hinder SAGS applications. In this study, “one-step” development strategy was used to try to directly cultivate SAGS under 9% salinity, and the fastest cultivation process was obtained under such high salinity compared to the previous papers with the inoculum of municipal activated sludge without bioaugmentation. Briefly, the inoculated municipal activated sludge was almost discharged on Day 1–10, then fungal pellets appeared and it gradually transitioned to mature SAGS (particle size of ∼4156 μm and SVI30 of 57.8 mL/g) from Day 11 to Day 47 without fragmentation. Metagenomic revealed that fungus Fusarium played key roles in the transition process probably because it functioned as structural backbone. RRNPP and AHL-mediated systems might be the main QS regulation systems of bacteria. TOC and NH4+-N removal efficiencies maintained at ∼93.9% (after Day 11) and ∼68.5% (after Day 33), respectively. Subsequently, the influent organic loading rate (OLR) was stepwise increased from 1.8 to 11.7 kg COD/m3·d. It was found that SAGS could maintain intact structure and low SVI30 (< 55 mL/g) under 9% salinity and the OLR of 1.8–9.9 kg COD/m3·d with adjustment of air velocity. TOC and NH4+-N (TN) removal efficiencies could maintain at ∼95.4% (below OLR of 8.1 kg COD/m3·d) and ∼84.1% (below nitrogen loading rate of 0.40 kg N/m3·d) in ultra-hypersaline environment. Halomonas dominated the SAGS under 9% salinity and varied OLR. This study confirmed the feasibility of direct aerobic granulation in ultra-hypersaline environment and verified the upper OLR boundary of SAGS in ultra-hypersaline high-strength organic wastewater treatment.

Study on copper oxide modified biochar for activating persulfate high efficiency and application for the removal of bisphenol A

AbstractAdvanced oxidation based on persulfate applied for the removal of organic pollutants has received widespread attention. Here, combining hydrothermal synthesis and a high‐temperature calcination approach, we constructed an effective copper oxide‐modified biochar from wood waste (Ginkgo biloba rods) for the removal of bisphenol A (BPA) from contaminated waterways. The modified biochar with copper oxide in its structure (CuO/BC) exhibited a densely arranged needle‐shaped structure different from pristine timber waste biochar (BC). CuO/BC can activate persulfate efficiently, and the removal rate of BPA could reach 100% within 20–30 min, approximately three times higher than that of BC. Moreover, CuO/BC was more suitable for treating BPA wastewater under alkaline conditions. The stability of CuO/BC, reaction intermediates, and possible degradation pathway were investigated. These results demonstrate the potential of the application of CuO/BC for organic wastewater treatment and shed light on a new approach to develop wastewater treatment materials that are carbon‐based and cost‐effective.

Life cycle assessment of high concentration organic wastewater treatment by catalytic wet air oxidation

There have been many studies on life cycle assessment in sewage treatment, but there are scarce few studies on the treatment of industrial wastewater in combination with advanced oxidation technology, especially in catalytic wet air oxidation (CWAO). There are no cases of using actual industrialized data onto life cycle assessment. This paper uses Simapro 9.0 software to establish a life cycle assessment model for the treatment of high-concentration organic wastewater by CWAO, and comprehensively explains the impact on the environment from three aspects: the construction phase, the operation phase and the demolition phase. In addition, sensitivity analysis and uncertainty analysis were performed. The results showed that the key factors affecting the environment were marine ecotoxicity, mineral resource consumption and global warming, the operation stage had the greatest impact on the environment, which was related to high power consumption during operation and emissions from the treatment process. Sensitivity analysis showed that electricity consumption has the greatest impact on abiotic depletion and freshwater aquatic ecotoxicity, and it also proved that global warming is mainly caused by pollutant emissions during operation phase. Monte Carlo simulations found slightly higher uncertainty for abiotic depletion and toxicity-related impact categories.

Research progress on key factors of dielectric-barrier discharge plasma for wastewater treatment

Plasma treatment of wastewater is known as a new advanced oxidation process (AOP), which has attracted extensive attention. Dielectric barrier discharge plasma has the characteristics of no vacuum pumping and high electron number density. It has outstanding application value in various forms of plasma. There are many coupling factors that affect the characteristics of dielectric barrier discharge plasma and the effect of wastewater treatment. Optimizing the key parameters is of great significance to improve the treatment efficiency and reduce the treatment cost. This paper introduces the principle, experimental device, potential advantages and application value of dielectric barrier discharge, summarizes the influence rules of key factors such as high voltage power supply characteristics, electrode configuration, carrier gas and reactor design on the characteristics of organic pollutant wastewater treatment by dielectric barrier discharge plasma. The optimization and matching of multiple factors are important problems. This paper provides a useful reference for the engineering application of plasma technology for wastewater treatment.

Efficient mineralization of organic pollutants in water via a phenol-responsive catalytic ozonation process

Background: Catalytic ozonation process has become one of the most promising technologies in organic wastewater treatment industry due to its high efficiency and rapidity. Some researchers have found that alkaline earth metal oxides can be used to promote the ozonation process to removal organic compound in wastewater. And some of them believe that calcium-based catalysts can effectively catalyze the ozonation reaction, but there are few reports about its reaction mechanism.Methods: In this work, calcium oxide was used as catalyst to study their effect in phenol wastewater and the mechanism of catalytic reaction process. In the catalytic ozonation process, the surface hydroxyl of solid CaO-based catalyst can react as the reaction active sites to promote the formation of free radicals, and the Ca2+ solutes in this system can promote the decomposition of H2O2 to produce free radicals. At the same time, the addition of calcium oxide-based catalyst also increases the pH of the reaction system, which is conducive to the decomposition of ozone to produce hydroxyl radicals. Owing to the presence of •OH, 1O2 and •O2−, phenol and by-product are decomposed effectively.Significant findings: The experimental results show that the COD removal rate of phenol reached ∼100% in 20 min. And in this study, the mechanism of CaO-based catalysts used in the ozonation process was studied. We found that both of Ca2+ in solution and solid calcium oxide promoted the formation of active free radicals in catalytic ozonation process.

Molybdenum disulfide co-catalysis boosting nanoscale zero-valent iron based Fenton-like process: Performance and mechanism

The conventional Fenton process has the drawbacks of low efficiency of Fe3+/Fe2+ conversion, low utilization of H2O2, and narrow range of pH. In this paper, molybdenum sulfide (MoS2) was used as a co-catalyst to boost the nanoscale zero-valent iron (nZVI) based heterogeneous Fenton-like process for the degradation of Rhodamine B (RhB). The catalytic performance, influences of parameters, degradation mechanism, and toxicity of intermediates were explored. Compared with the conventional like-Fenton process, the existence of MoS2 accelerated the decomposition of H2O2 and the RhB degradation rate constant of MoS2/nZVI/H2O2 reached more than six times that of nZVI/H2O2. In addition, the effective pH range of MoS2/nZVI/H2O2 was broadened to 9.0 with 84.9% of RhB being removed within 15 min. The co-catalytic system of MoS2 and nZVI was stable and had high reusability according to the results of four consecutive runs. Quenching tests and electron paramagnetic resonance (EPR) demonstrated that hydroxyl radical (·OH), superoxide anions (·O2−), and singlet oxygen (1O2) were all involved in MoS2/nZVI/H2O2. Compared with nZVI/H2O2 system, MoS2 not only increased the corrosion of nZVI but also accelerated the conversion of Fe3+/Fe2+. ECOSAR analysis suggested that the overall acute and chronic toxicity of the degradation products decreased after treatment. Hence, this MoS2 co-catalytic nZVI based Fenton-like process can be used as a promising alternative for the treatment of organic wastewater.

Heterogeneous Electro-Fenton-Catalyzed Degradation of Rhodamine B by Nano-Calcined Pyrite

The use of natural pyrite as a catalyst for the treatment of recalcitrant organic wastewater by an electro-Fenton system (pyrite-EF) has recently received extensive attention. To improve the catalytic activity of natural pyrite (Py), magnetic pyrite (MPy), and pyrrhotite (Pyr), they were obtained by heat treatment, and the nanoparticles were obtained by ball milling. They were characterized by X-ray diffraction, X-ray electron spectroscopy, and scanning electron microscopy. The degradation performance of rhodamine B (Rhb) by heterogeneous catalysts was tested under the pyrite-EF system. The effects of optimal pH, catalyst concentration, and current density on mineralization rate and mineralization current efficiency were explored. The results showed that the heat treatment caused the phase transformation of pyrite and increased the relative content of ferrous ions. The catalytic performance was MPy > Py > Pyr, and the Rhb degradation process conformed to pseudo-first-order kinetics. Under the optimum conditions of 1 g L-1 MPy, an initial pH of five, and a current density of 30 mA cm-2, the degradation rate and TOC removal rate of Rhb wastewater reached 98.25% and 77.06%, respectively. After five cycles of recycling, the chemical activity of MPy was still higher than that of pretreated Py. The main contribution to Rhb degradation in the system was •OH radical, followed by SO4•-, and the possible catalytic mechanism of MPy catalyst in the pyrite-EF system was proposed.

Cu atoms on UiO-66-NH2/ZnIn2S4 nanosheets enhance photocatalytic performance for recovering hydrogen energy from organic wastewater treatment

The extensive use of sacrificial agents and the low carrier separation and utilization efficiency remain important factors limiting the development of photocatalytic hydrogen production. We report a three-layered, dual-functional photocatalysts of Cu atomics@UiO-66-NH2(U6N)/ZnIn2S4 nanosheets (ZIS), for the simultaneous production of photocatalytic hydrogen and degradation of organic pollutants. When common and highly toxic organic pollutants (phenolic compounds and antibiotics) were substituted for the sacrificial agents, Cu@U6N/ZIS exhibited superior sustained hydrogen production, approximately 28 times greater than that of pure ZIS. The experimental results suggested that the window size of U6N (< organic pollutants molecular size) separates the reaction sites of organic pollutants oxidation and reduction of hydrogen ions (H+), thereby achieving spatial separation of redox sites. Besides, the structure of Cu@U6N/ZIS, which was anchored Cu within U6N and encapsulated by ZIS nanosheets, forming Z-type heterojunctions, achieved the control of the directional transfer of photogenerated electrons. And the coupled system can effectively enhance water quality by reducing the biological toxicity of the wastewater. This study suggests new avenues for environmental restoration and non-fossil fuel production.

Oxidized dextran-crosslinked ferrocene-chitosan-PEI composite porous material integrating adsorption and degradation to malachite green

Treating wastewater containing malachite green (MG) using porous materials with both adsorption and degradation functions have become a major challenge in achieving the carbon neutrality goal. Herein by incorporating the ferrocene (Fc) group as a Fenton active center, a novel composite porous material (DFc-CS-PEI) was prepared using chitosan (CS) and polyethyleneimine (PEI) as skeletons and oxidized dextran as a crosslinker. DFc-CS-PEI not only possesses satisfactory adsorption performance to MG but also excellent degradability in the presence of a minor amount of H2O2 (3.5 mmol/L) without any additional assistance, due to high specific surface area and active Fc group. The maximum adsorption capacity is ca. 177.73 ± 3.11 mg/g, outperforming most CS-based adsorbents. The removal efficiency of MG is significantly enhanced from 20 % to 90 % as DFc-CS-PEI and H2O2 coexist, due to ·OH-dominated Fenton reaction, and remained in a wide pH range (2.0–7.0). Cl− exhibits notable suppression on the degradation of MG because of quenching effects. Note that DFc-CS-PEI has a very small iron leaching (0.2 ± 0.015 mg/L), and can be rapidly recycled by simple water-washing, without any harmful chemicals and potential second pollution. Such versatility, high stability, and green recyclability make the as-prepared DFc-CS-PEI a promising porous material for the treatment of organic wastewater.

Peroxymonosulfate activation by graphene oxide-supported 3D-MoS2/FeCo2O4 sponge for highly efficient organic pollutants degradation

To address conventional powder catalysts' recovery and aggregation issues that greatly restrain their practical application, a recoverable graphene oxide (GO)-supported 3D-MoS2/FeCo2O4 sponge (SFCMG) was developed through a simple impregnation pyrolysis method. SFCMG can efficiently activate peroxymonosulfate (PMS) to produce reactive species for rapid degradation of rhodamine B (RhB), with 95.0% and 100% of RhB being removed within 2 min and 10 min, respectively. The presence of GO enhances the electron transfer performance of the sponge, and the three-dimensional melamine sponge serves as a substrate to provide a highly dispersed carrier for FeCo2O4 and MoS2/GO hybrid sheets. SFCMG exhibits a synergistic catalytic effect of Fe and Co, and facilitates the redox cycles of Fe(III)/Fe(II) and Co(III)/Co(II) by MoS2 co-catalysis, which enhances its catalytic activity. Electron paramagnetic resonance results demonstrate that SO4•−, ·O2− and 1O2 are all involved in SFCMG/PMS system, and 1O2 played a prominent role in RhB degradation. The system has good resistance to anions (Cl−, SO42−, and H2PO4−) and humic acid and excellent performance for many typical contaminants degradation. Additionally, it works efficiently over a wide pH range (3–9) and possesses high stability and reusability with the metal leaching far below the safety standards. The present study extends the practical application of metal co-catalysis and offers a promising Fenton-like catalyst for the treatment of organic wastewater.

A novel iron molybdate photocatalyst with heterojunction-like band gap structure for organic pollutant degradation by activation of persulfate under simulated sunlight irradiation.

Advanced oxidation processes (AOPs) applied to wastewater treatment have become increasingly well developed and the ability of a single technology to remove difficult organic pollutants is limited. One of the main limiting factors is the insufficient variety and quantity of active species generated during the reaction process and catalyst failure. The coupling of the two methods is a practical and effective approach. In this study, different types of semiconductor persulfate (PS) activators, iron molybdate nanoparticles (I-FeMoO4, II-FeMoO4, and III-FeMoO4), were synthesized by simple solvothermal and calcination methods and applied to photo-assisted activation of PS systems. In addition, the relationship between the intrinsic physicochemical and optoelectronic properties of FeMoO4 and the catalytic degradation performance was revealed by a series of characterization tools, and the dominant catalysts were screened. At an unadjusted pH of 4.86, 0.6g L-1 of PS and 0.4g L-1 of I-FeMoO4 could achieve efficient degradation of several difficult organic dye contaminants (rhodamine b (Rh B), methylene blue (MB), malachite green (MG), methyl orange (MO), and tartrazine (TTZ)) and other antibiotic contaminants (sulfamethoxazole (SMX), tetracycline (TC), norfloxacin (NOR), and carbamazepine (CBZ)) within 5-60min. Possible degradation mechanisms in the I-FeMoO4/PS/Light reaction system were suggested by radical trapping experiments and electron paramagnetic resonance (EPR) tests. Recovery tests demonstrated that I-FeMoO4 has good recoverable stability and did not cause secondary pollution. Finally, our study provided a new perspective on the application of coupled wastewater treatment technologies in the practical treatment of organic wastewater.