Specifically enhancement of heterogeneous Fenton-like degradation activities for ofloxacin with synergetic effects of bimetallic Fe-Cu on ordered mesoporous silicon

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite derived from lignin: an efficient peroxymonosulfate activator for naphthalene degradation

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite (Fe-Cu-N-PC) was prepared via direct pyrolysis by employing black liquor lignin as a main precursor, and it was utilized as a novel catalyst for PMS activation in degrading naphthalene. Under the optimum experimental conditions, the naphthalene degradation rate was up to 93.2% within 60 min in the Fe-Cu-N-PC/PMS system. The porous carbon framework of Fe-Cu-N-PC could facilitate the quick molecule diffusion of reactants towards the inner bimetallic nanoparticles and enriched naphthalene molecules from the solution by a specific adsorption, which increased the odds of contact between naphthalene and reactive oxygen species and improved the reaction efficiency. The quenching reaction proved that the non-free radical pathway dominated by 1O2 was the main way in naphthalene degradation, while the free radical pathway involving SO4·- and ·OH only played a secondary role. Moreover, owing to its high magnetization performance, Fe-Cu-N-PC could be magnetically recovered and maintained excellent naphthalene degradation rate after four degradation cycles. This research will offer a theoretical basis for the construction of facile, efficient, and green technologies to remediate persistent organic pollutants in the environment.

Highly efficient decomplexation of chelated nickel and copper effluent through CuO-CeO2-Co3O4 nanocatalyst loaded on ceramic membrane

A novel CuO-CeO₂-Co₃O₄ nanocatalyst loaded on Al₂O₃ ceramic composite membrane (CCM-S) was synthesized through spraying-calcination method, which can be beneficial to the engineering application of scattered granular catalyst. BET and FESEM-EDX testing revealed that CCM-S possessed a porous character with high BET surface area of 22.4 m²/g and flat modified surface with extremely fine particle aggregation. The CCM-S calcined above 500 °C presented excellent anti-dissolution effect due to the formation of crystals. XPS indicated that the composite nanocatalyst possessed the variable valence states, which were conducive to exert the catalytic effect of Fenton-like reaction. Subsequently, the effects of experimental parameters including fabricate method, calcination temperature, H₂O₂ dosage, initial pH value, and CCM-S amount were further investigated considering the removal efficiency of Ni(II)-complex and COD after decomplexation and precipitation (pH = 10.5) treatment within 90 min. Under the optimal reaction condition, the residual Ni(II)-complex and Cu(II)-complex concentration from actual wastewater was all lower than 0.18 mg/L and 0.27 mg/L, respectively; meanwhile, the removal efficiency of COD was all higher than 50% in the mixed electroless plating effluent. Besides, the CCM-S could still maintain high catalytic activity after a six-cycle test, and the removal efficiency was slightly declined from 99.82% to 88.11%. These outcomes indicated that CCM-S/H₂O₂ system was provided with a potential applicability on treatment of real chelated metal wastewater.

Novel catalysts with multivalence copper for organic pollutants removal from wastewater with excellent selectivity and stability in Fenton-like process under neutral pH conditions

Fenton-like reaction has been widely used for organics degradation. However, most Fenton-like reaction works at low pH range (pH < 4) with uncontrollable selectivity of hydroxyl radicals from H₂ O₂ activation, and unsatisfied catalyst stability, which is compromised advanced oxidation performance for water/wastewater treatments. In this work, to solve the drawbacks, novel copper catalysts were fabricated via hydrogen reduction/calcination of Cu²⁺ -supported Al/MCM-41 with precisely controllable copper valence state. Compared with catalysts with monovalence copper (i.e., CuO, Cu, and Cu²⁺ ), the obtained catalysts with multivalence copper present higher selectivity, excellent stability towards •OH radical pathways, and outperformance in pCBA degradation efficiency at neutral state. In addition, the fabricated catalysts also exhibited excellent phenol removal efficiency (75.5%) and H₂ O₂ utilization efficiency (47.9%) within neutral environment. Moreover, the degradation efficiency of phenol approaches to 100% within only 2 h. The catalyst also shows good stability for organic pollutants removal, which shows good potential in catalytic oxidation for phenolic compounds-containing wastewater in Fenton-like reaction, especially under neutral pH conditions. PRACTITIONER POINTS: Multivalence copper presents great potentials for organic compounds removal at neutral condition. Multivalence copper shows higher selectivity toward •OH and good stability at neutral condition. Multivalence copper exhibiters outperformed phenol removal efficiency at neutral condition.

Effect of soil sulfamethoxazole on strawberry (Fragaria ananassa): Growth, health risks and silicon mitigation

The negative impact of antibiotic pollution on the agricultural system and human health is a hot issue in the world. However, little information is available on the antibiotics toxicity mechanism and the role of silicon (Si) to alleviate the antibiotics toxicity. In this study, strawberry (Fragaria ananassa) showed excitatory response to low-dose SMZ (1 mg L^-1), but strawberry root and photosynthetic efficiency were damaged under high level. When SMZ level exceeded 10 mg L^-1, H₂0₂, O₂^-, MDA and relative conductivity increased, while SOD and CAT activities first increased and then decreased. SMZ accumulated more in roots and fruits, but less in stems, and the accumulation increased with the increase of SMZ-dose. Under 1 mg L^-1 SMZ, the SMZ accumulation in fruits was 110.54 μg kg^-1, which exceeded the maximum residue limit. SMZ can induce the expression of sul1, sul2 and intI1, and intI1 had the highest abundance. Exogenous application of Si alleviated the toxicity of SMZ, which is mainly related to the degradation of SMZ in soil and the reduction of SMZ absorption by strawberry. In addition, Si relieved root damage, promoted the increase of photosynthetic efficiency, and improved the antioxidant system to resist SMZ toxicity.

Fe-based Fenton-like catalysts for water treatment: Preparation, characterization and modification

Fenton reaction based on hydroxyl radicals () is effective for environment remediation. Nevertheless, the conventional Fenton reaction has several disadvantages, such as working at acidic pH, producing iron-containing sludge, and the difficulty in catalysts reuse. Fenton-like reaction using solid catalysts rather than Fe²⁺ has received increasing attention. To date, Fe-based catalysts have received increasing attention due to their earth abundance, good biocompatibility, comparatively low toxicity and ready availability, it is necessary to review the current status of Fenton-like catalysts. In this review, the recent advances in Fe-based Fenton-like catalysts were systematically analyzed and summarized. Firstly, the various preparation methods were introduced, including template-free methods (precipitation, sol gel, impregnation, hydrothermal, thermal, and others) and template-based methods (hard-templating method and soft-templating method); then, the characterization techniques for Fe-based catalysts were summarized, such as X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET), SEM (scanning electron microscopy)/TEM (transmission electron microscopy)/HRTEM (high-resolution TEM), FTIR (Fourier transform infrared spectroscopy)/Raman, XPS (X-ray photoelectron spectroscopy), ⁵⁷Fe Mössbauer spectroscopy etc.; thirdly, some important conventional Fe-based catalysts were introduced, including iron oxides and oxyhydroxides, zero-valent iron (ZVI) and iron disulfide and oxychloride; fourthly, the modification strategies of Fe-based catalysts were discussed, such as microstructure controlling, introduction of support materials, construction of core-shell structure and incorporation of new metal-containing component; Finally, concluding remarks were given and the future perspectives for further study were discussed. This review will provide important information to further advance the development and application of Fe-based catalysts for water treatment.

Preparation of a Gangue-Based X-type Zeolite Molecular Sieve as a Multiphase Fenton Catalyst and Its Catalytic Performance

In this study, a series of X-type zeolite molecular sieve catalysts, modified with copper (Cu-X), were prepared by an alkali fusion-hydrothermal synthesis using coal gangue from Inner Mongolia. These catalysts were used in the degradation of the methylene blue dye by a Fenton-like reaction. Characterization results showed that Cu is considered to be present in the surface structure of the zeolite in the form of doped Cu ions and metal oxide. It is believed that Cu2+ is the main active site involved in the Fenton reaction. The X-ray photoelectron spectroscopy (XPS) spectra indicated that Cu2+ and Cu+ coexist in the catalysts and participate together in the Fenton reaction. The degradation of methylene blue by the Cu-X catalysts was investigated to determine the optimal catalytic conditions in terms of six aspects: catalyst dosage, initial solution concentration, initial pH of the solution, H2O2 dosage, copper loading, and reaction temperature. The experimental results showed that CX-1.0 had excellent activity and stability for the degradation and decolorization of the methylene blue dye, which could completely degrade the dye within 90 min, and the total organic carbon removal rate reached as high as 97.8%. Electron spin resonance (ESR) and radical capture experiments showed that •OH played a dominant role in the Fenton-like reaction. Combined with XPS, ESR, and catalytic tests, the redox cycle of Cu+/Cu2+ was found to be accelerating the generation of reactive radicals in the Fenton system.

Heterogeneous Fenton degradation of ofloxacin catalyzed by magnetic nanostructured MnFe2O4 with different morphologies

Magnetic nanostructured MnFe₂O₄ with different morphologies, synthesized via chemical co-precipitation and hydrothermal method, was assayed as heterogeneous Fenton catalysts. The as-prepared MnFe₂O₄ catalysts were thoroughly characterized by various characterization methods, such as X-ray diffraction (XRD), N₂ adsorption-desorption, transmission electron microscopy (TEM), magnetic hysteresis loops, temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The catalytic activity of MnFe₂O₄ catalysts was evaluated in the heterogeneous Fenton degradation of ofloxacin (OFX). In our study, the morphology exhibited a critical impact on the catalytic activity of MnFe₂O₄. For example, MnFe₂O₄ nanorods (MnFe₂O₄-NR) had a higher catalytic activity than MnFe₂O₄ nanospheres (MnFe₂O₄-NS) and MnFe₂O₄ nanocubes (MnFe₂O₄-NC) in OFX removal and H₂O₂ decomposition. Notably, the catalytic activity was remarkably enhanced with increasing the relative amount of Mn³⁺ and Fe²⁺ species on the surface. Based on the results from quenching experiments and quantitative determination of •OH radicals, a possible catalytic mechanism of MnFe₂O₄ was proposed. In addition, the stability and reusability of MnFe₂O₄-NR was ascertained, as the results suggested that MnFe₂O₄-NR was a stable and easily separated catalyst for heterogeneous Fenton process.

Enhanced Photo–Fenton Removal Efficiency with Core-Shell Magnetic Resin Catalyst for Textile Dyeing Wastewater Treatment

Heterogeneous photo–Fenton reactions have been regarded as important technologies for the treatment of textile dyeing wastewaters. In this work, an efficient core-shell magnetic anion exchange resin (MAER) was prepared through in situ polymerization and used to remove reactive brilliant red (X-3B) in a UV–Fenton system. The MAER exhibited satisfactory removal efficiency for X-3B because of its highly effective catalytic activity. More than 99% of the X-3B (50 mg/L) was removed within 20 min in the UV–Fenton reaction. This is because the uniformly dispersed core-shell magnetic microsphere resin could suppress the aggregation of Fe3O4 nanoparticles and, thus, enhance the exposure of Fe reaction sites for catalytic reaction with H2O2. The good adsorption capacity of MAER also played an important role in promoting contact between X-3B and reactive radicals during the reaction. Mechanism research showed that hydroxyl radical (•OH) was the main reactive radicals for the removal of X-3B in the MAER UV–Fenton system. The MAER can be easily separated by a magnet after catalytic reactions. Moreover, the matrix effects of different substrates (Cl−, NO3−, SO42−, and humic acid) were investigated. The results showed that SO42− could be beneficial to improve the removal of X-3B but that the others decrease the removal. The MAER UV–Fenton also removed significant amounts of total organic carbon (TOC) for the X-3B solution and an actual textile dyeing industrial wastewater. The heterogeneous oxidation system established in this work may suggest prospects for practical applications in the treatment of textile dyeing wastewater.

Fabrication, application, optimization and working mechanism of Fe2O3 and its composites for contaminants elimination from wastewater

Fe₂O₃ and its composites have been extensively investigated and employed for the remediation of contaminated water with the characteristics of low cost, outstanding chemical stability, high efficiency of visible light utilization, excellent magnetic ability and abundant active sites for adsorption and degradation. In this review, the potentials of Fe₂O₃ in water remediation were discussed and summarized in detail. Firstly, various synthesis methods of Fe₂O₃ and its composites were reviewed and compared. Based on the structures and characteristics of the obtained materials, their applications and related mechanisms in pollutants removal were surveyed and discussed. Furthermore, several strategies for optimizing the remediation processes, including dispersion, immobilization, nano/micromotor construction and simultaneous decontamination, were also highlighted and discussed. Finally, recommendations for further work in the development of novel Fe₂O₃-related materials and its practical applications were proposed.

Fe3O4-Zeolite Hybrid Material as Hetero-Fenton Catalyst for Enhanced Degradation of Aqueous Ofloxacin Solution

A hetero-Fenton catalyst comprising of Fe3O4 nanoparticles loaded on zeolite (FeZ) has been synthesized using a facile co-precipitation method. The catalyst was characterized using various characterization methods and then, subsequently, was used to degrade ofloxacin (OFL, 20 mg·L−1), an antibiotic, via a heterogeneous Fenton process in the presence of an oxidizing agent. The effects of different parameters such as Fe3O4 loading on zeolite, catalyst loading, initial solution pH, initial OFL concentration, different oxidants, H2O2 dosage, reaction temperature, and inorganic salts were studied to determine the performance of the FeZ catalyst towards Fenton degradation of OFL under different conditions. Experimental results revealed that as much as 88% OFL and 51.2% total organic carbon (TOC) could be removed in 120 min using the FeZ catalyst. Moreover, the FeZ composite catalyst showed good stability for Fenton degradation of OFL even after five cycles, indicating that the FeZ catalyst could be a good candidate for wastewater remediation.

Recent advances in Cu-Fenton systems for the treatment of industrial wastewaters: Role of Cu complexes and Cu composites

Cu-based Fenton systems have been recognized as a promising suite of technologies for the treatment of industrial wastewaters due to their high catalytic oxidation capacity. Rapid progress regarding Cu Fenton systems has been made not only in fundamental mechanistic aspects of these systems but also with regard to applications over the past decade. Based on available literature, this review synthesizes the recent advances regarding both the understanding and applications of Cu-based Fenton processes for industrial wastewater treatment. Cu-based catalysts that are essential to the effectiveness of use of Cu Fenton reactions for oxidation of target species are mainly classified into two types: (i) Cu complexes with organic or inorganic ligands, and (ii) Cu composites with inorganic materials. Performance of the Cu-based catalysts for the removal of organic pollutants in industrial wastewaters are reviewed, with the key operating parameters illustrated. Furthermore, the roles of Cu complexes and composites in both homogeneous and heterogeneous Cu-Fenton systems are critically examined with particular focus on the mechanisms involved. Perspectives and future efforts needed for Cu-based Fenton systems using Cu complexes and composites for industrial wastewater treatment are presented.

Degradation of antibiotics by advanced oxidation processes: An overview

Antibiotics are becoming emerging contaminants due to their extensive production and consumption, which have caused hazards to the ecological environment and human health. Various techniques have been studied to remove antibiotics from water and wastewater, including biological, physical and chemical methods. Among them, advanced oxidation processes (AOPs) have received increasing attention due to their fast reaction rate and strong oxidation capability, which are effective for the degradation of antibiotics in aquatic environments. In this review paper, a variety of AOPs, such as Fenton or Fenton-like reaction, ozonation or catalytic ozonation, photocatalytic oxidation, electrochemical oxidation, and ionizing radiation were briefly introduced, including their principles, characteristics, main influencing factors and applications. The current applications of AOPs for the degradation of antibiotics in water and wastewater were analyzed and summarized, the concluding remarks were given and their future perspectives and challenges were discussed.

A novel discovery of a heterogeneous Fenton-like system based on natural siderite: A wide range of pH values from 3 to 9

Natural iron-bearing minerals have been proven to be effective for activating H₂O₂ to produce OH, which can be used to degrade organic pollutants. In this study, the performance of siderite to degrade sodium sulfadiazine via catalytic H₂O₂ degradation was investigated at different solution pH values from 3 to 9. An interesting discovery was made: the performance of the siderite-H₂O₂ system was excellent under acidic, neutral, and even alkaline conditions. The influence of various factors (e.g. initial concentration, anions, natural organic matters, etc.) on the system under different pH conditions was investigated, which confirmed that siderite exhibited an excellent catalytic performance. By combining EPR characterization with scavenger research, it was proposed that dissolved iron (Fe²⁺) mainly initiated the homogenous Fenton reaction to degrade pollutants under acidic conditions, while structural Fe²⁺ species present in siderite triggered Fenton-like reactions under neutral or even alkaline conditions. From the SEM and XPS characterizations, oxidation and dissolution of Fe²⁺ on the surface were also observed, confirming our inference concerning the different reaction mechanisms. The experimental findings show that this siderite-H₂O₂ system can be used in solutions with pH values from 3 to 9 and that siderite plays a positive role in soil and groundwater remediation when H₂O₂ is used as an oxidant.

Waste control by waste: Fenton-like oxidation of phenol over Cu modified ZSM-5 from coal gangue

Coal gangue and phenol are two main pollutants in coal mining and processing. Using coal gangue as raw material, a series of Cu modified ZSM-5 (Cu/ZSM-5) catalysts were developed to remove phenol through heterogeneous Fenton-like reaction. This procedure implies the concept of waste control by waste. The characterization results showed that Cu modification had no obvious impact on the MFI (Mobile Five) structure of ZSM-5. Copper ions were presented as doping element (substitution of Na and Al ions) and copper oxides on ZSM-5 surface. The XPS spectra suggested the co-existence of Cu²⁺ and Cu⁺. As a consequence of well-defined experimental parameters, 7% Cu/ZSM-5 performed excellent activity and stability for the degradation and mineralization of phenol pollutant, which could degrade phenol completely within 30min and the TOC removal efficiency could reach 63% within 60min and 92% within 8h. ESR and radicals capturing experiments demonstrated that OH and ¹O₂ played the dominant roles in the Fenton-like reaction. In combination with XPS, ESR and catalytic tests, it's found that the redox cycling of Cu⁺/Cu²⁺ played critical roles in accelerating the active radical generation in this Fenton-like system.

Efficient degradation of AO7 by ceria-delafossite nanocomposite with non-inert support as a synergistic catalyst in electro-fenton process

CuFeO₂/CeO₂ as a novel catalyst was synthesized and its catalytic performance was evaluated for electro-Fenton degradation of acid orange 7 (AO7). It was demonstrated from the characterization results that the rhombohedral structure of CuFeO₂ and face-centered cubic fluorite structure of CeO₂ remained stable after nanocomposite construction. The impact of such operating parameters as pH, current intensity and, catalyst amount was investigated and the optimum conditions (100 mgL^-1 AO7, pH 3, 150 mgL^-1 CuFeO₂/CeO₂, I: 150 mA) determination led to 99.3% AO7 removal and 79.1% COD removal in 60 min. The introduction of CeO₂ as non-inert support had a significant impact on H₂O₂ electro-generation as an important step in AO7 removal. CuFeO₂/CeO₂ presented negligible metal leaching (iron 4.13%, copper 2.4%, and cerium 0.33%) which could be due to the strong interaction between active species and support. The nanocomposite performed efficiently in salty systems and two samples of real wastewaters due to Brønsted acidity character of ceria, which makes it a potential choice in industrial applications. The good performance of nanocomposite could be the result of the synergistic effect between Fe, Cu, and Ce. Regarding scavenging measurements results, the electro-Fenton process followed the Haber-Weiss mechanism. The by-products detection was performed using GC-MS analysis to propose an acceptable pathway for EF degradation of AO7. The BMG kinetics model (1/b = 0.969 (min) and 1/m = 0.269 (min^-1)) was matched with the experimental data and described the kinetics of reaction very well. The catalytic activity of CuFeO₂/CeO₂ almost remained after six cycles. Based on the obtained results, CuFeO₂/CeO₂ using the benefit of the synergistic effect of Ce³⁺ with Fe²⁺ and Cu⁺can be introduced as a promising novel catalyst for the electro-Fenton reaction in wastewater treatment.

Cellulose Conversion to 5 Hydroxymethyl Furfural (5-HMF) Using Al-Incorporated SBA-15 as Highly Efficient Catalyst

Al-incorporated SBA-15 samples (xAl/SBA-15) were successfully prepared by “atomic implantation” method. The samples were characterized by X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), N2 adsorption-desorption isotherms (BET), and temperature-programmed desorption (NH3-TPD). In this catalyst, metal oxide species were highly dispersed on the SBA-15 surface and existed as isolated atoms. It was shown that the Al incorporation lead to the formation of medium and strong acid sites. The catalytic activity and selectivity were tested in a mild hydrothermal process for degradation of cotton cellulose to 5-hydroxymethyl furfural (5-HMF). A cellulose conversion of 68.5% and 5-HMF selectivity of 62.1% after 2 h of reaction at 170°C were achieved. The very high 5-HMF yield (42.57%) obtained in this paper is much higher than that was reported in the literature.

Preparation of Iron-Loaded Granular Activated Carbon Catalyst and Its Application in Tetracycline Antibiotic Removal from Aqueous Solution

The removal of tetracycline antibiotics from water is currently an important environmental issue. Here we prepared an iron-loaded granular activated carbon catalyst (GAC-Fe) through a one-step calcination method to remove tetracycline antibiotics from aqueous solution. The GAC-Fe was characterized by Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. The effect of different influencing factors on the removal behavior of tetracycline antibiotics was studied, such as the solid-to-liquid ratio, H2O2 dosage, environmental temperature, initial pH, and contact time. The removal mechanism was explored through Fe ion dissolution and a free radical quenching experiment. The results show that the optimum solid-to-liquid ratio was 3.0 g∙L-1 and the suitable H2O2 dosage was 1.0 mL (3%). The applicable environmental temperature was 25 °C and the appropriate pH value was 2.0. The removal rate of tetracycline antibiotics tended to be stable in a contact time of 600 min. The main mechanism of tetracycline antibiotic removal by GAC-Fe was heterogeneous catalytic reaction through iron ion leaching and free radical inhibition experiment. The hydroxyl radical played a major role during the removal process. The partially dissolved iron ions initiated a homogeneous catalytic reaction. However, heterogeneous catalytic degradation was the main reaction. The GAC-Fe could still remove tetracycline antibiotics after five cycles, especially for methacycline and minocycline. Our work suggests that the GAC-Fe catalyst has potential as a remediation agent for tetracycline antibiotics in aqueous solution.

Enhanced degradation of sulfamethoxazole by Fe-Mn binary oxide synergetic mediated radical reactions

In this study, a novel Fe-Mn binary oxide (FMBO), which combined the oxidation capability of iron and manganese oxides, was constructed to remove sulfamethoxazole (SMX) effectively using the simultaneous co-precipitation and oxidation methods, and the reaction products were probed by liquid chromatography-mass spectrometry (LC/MS). Particularly, FMBO-mediated transformation mechanisms of SMX were explored using radical scavengers and electron paramagnetic resonance (EPR). Results indicated that the best removal efficiency was obtained at a pH of 4.0, with the H₂O₂ of 6.0 mmol/L and the FMBO dosage of 2.0 g/L, giving 97.6% removal of 10 mg/L SMX within 60 min. More importantly, we found that the hydroxyl (•OH) radicals generated by FMBO through Fenton-like reaction were responsible for the SMX oxidation. EPR studies were confirmed that the peak intensities of hydroxyl adduct decreased remarkably with increasing pH values. Moreover, the four SMX degradation intermediate products were detected by LC/MS and a reaction pathway for the possible mineralization of SMX, with •OH radicals as the main oxidant, was proposed. These findings provide a novel insight into the removal of SMX by FMBO-mediated radical reactions in aquatic environments. Moreover, this research suggested that FMBO can act as an efficient catalyst to remove SMX in hospital wastewater.

A microwave-activated coal fly ash catalyst for the oxidative elimination of organic pollutants in a Fenton-like process

Raw coal fly ash was first activated by microwave irradiation to promote its catalytic potential and then used as a Fenton-like catalyst to treat polyacrylamide-contaminated wastewater. The optimal activation conditions of the raw coal fly ash (microwave power = 700 W, irradiation time = 10 min, mixing speed = 120 rpm, and raw coal fly ash loading = 20 g L-1) were determined by the orthogonal test. The significance of each effective parameter follows the order: raw coal fly ash loading > microwave power > irradiation time > mixing speed. Microwave irradiation can change the surface morphology and remarkably increase the specific surface area and pore volume. More than 75% of the TOC in the polyacrylamide-contaminated wastewater can be removed under the optimized treatment conditions ([H2O2] = 12 mg L-1, catalyst loading = 10 g L-1, [polyacrylamide] = 200 mg L-1, T = 313 K). The kinetic study shows that the variation in the catalyst loading and the polyacrylamide concentration can change the degradation path of the polyacrylamide, whereas the variation in the H2O2 dosage can accelerate the degradation of polyacrylamide. The Fenton-like process studied herein has a wider optimal pH range (2-5) than that of the classic Fenton process (3). The catalyst has weak catalytic capacity but better catalytic persistence than that of Fe2+. During the five runs of the catalyst, some heavy metallic and toxic elements (Fe, Al, Ti, Cr, Mn, etc.) can be detected but under the limits of the GB8978-1996 standard. Leaching can weaken the catalytic capacity (i.e., stability) of the catalyst. The catalytic process is caused by the synergism of multiple metals and consists of heterogeneous and homogeneous processes.

Heterogeneous fenton-like degradation of ofloxacin over sludge derived carbon as catalysts: Mechanism and performance

In this study, heterogeneous Fenton-like degradation of ofloxacin (OFX) was investigated by sludge derived carbon (SC). The effects of SC catalyst, temperature and pH on the efficiency of ofloxacin degradation were investigated. SC treated with sulfuric acid (SC-H₂SO₄) performed high catalytic activity, indicating that sulfate group produced low pH of the surface and was beneficial for heterogeneous Fenton-like degradation. The removal of ofloxacin and TOC was 91.5% and 62.3%, respectively, after 180 min adsorption and 540 min oxidation, at pH 6 and a dosage of 138 mg L^-1 H₂O₂. It was found that OFX conversion increased with the decrease of pH and OFX was degraded under the wide range of pH (3-6) by SC-H₂SO₄. These promising results clearly demonstrate the potential of the heterogeneous Fenton-like process for the effective degradation of ofloxacin by SC-H₂SO₄. Based on intermediated products identified by gas chromatography-mass spectrometry, a possible OFX oxidation pathway in Fenton-like reaction was proposed.

Nanoparticles of magnetite anchored onto few-layer graphene: A highly efficient Fenton-like nanocomposite catalyst

Developing a catalyst with high efficiency and recyclability is an important issue for the heterogeneous Fenton-like systems. In this study, magnetic Fe₃O₄ and reduced graphene oxide (RGO) nanocomposites were prepared by a facile alkaline-thermal precipitation method and employed as a highly effective heterogeneous Fenton-like catalyst for methyl orange (MO) degradation. Characterization of these nanocomposites by XRD, FTIR, Raman, FESEM and TEM revealed that nanoparticles (NPs) of Fe₃O₄ were tightly anchored on the few-layer RGO sheets. The anchoring of Fe₃O₄ NPs and the reduction of GO were achieved in one pot without adding any other reducing agents. Based on the measurements of GO surface Zeta potentials, a possible anchoring mechanism of Fe₃O₄ NPs onto RGO sheets was given. The Fe₃O₄/RGO nanocomposites exhibited much higher Fenton-like catalytic efficiency for MO degradation than pure Fe₃O₄ NPs. This degradation process followed the first-order kinetics model, where k₁ and T complied with the Arrhenius equation with E_a of 12.79 kJ/mol and A of 8.20 s^-1. Magnetic measurements revealed that Fe₃O₄/RGO nanocomposites were ferromagnetic as indicated by the presence of magnetic hysteresis loops. The Fe₃O₄/RGO nanocomposites showed good stability and recyclability. Hydroxyl radicals, OH were determined as the dominant oxidative species in Fe₃O₄/RGO-H₂O₂ system and the Fenton-like mechanism for MO degradation in water was proposed and discussed.

Treatment of Cutting Fluid Waste using Activated Carbon Fiber Supported Nanometer Iron as a Heterogeneous Fenton Catalyst

Addressing the problem of high chemical oxygen demands (COD) of cutting fluid waste generated in the machining process, its complex composition, and the specific conditions required for the treatment process, a heterogeneous Fenton fibre catalyst (NZVI@ACF) made of nanometer-iron supported on activated carbon fiber using dip-molding was developed. NZVI was homogeneously loaded onto ACF surfaces to form NZVI@ACF, with a specific surface area (S_BET) of 726.3642 m²/g. Using a multistage chemical pretreatment, the NZVI@ACF/H₂O₂ system was used to effectively treat cutting fluid waste. The results indicated that the rate of COD removal in the cutting fluid waste liquid pretreated with NZVI@ACF/H₂O₂ system was 99.8% when the reactions conditions were optimized to 20 nmol/L H₂O₂, 6 g/L NZVI@ACF, total reaction time of 120 min and pH 5. The treated waste solution passed China’s tertiary wastewater discharge standards. NZVI@ACF/H₂O₂ demonstrated an excellent catalytic performance compared to the traditional Fenton catalyst, increased the effective pH reaction range and had an adsorption effect on the waste liquid after the reaction.

Comparative study of Cu-based bimetallic oxides for Fenton-like degradation of organic pollutants

In order to provide useful information for the rational design of effective Fenton-like catalyst, a series of Cu-based bimetallic oxides were synthesized and their Fenton-like performances for the degradation of Orange II and ciprofloxacin were compared. The structure, chemical oxidation state, surface charge property and redox ability of the catalysts were also investigated by different characterization techniques. Among them, NiCu exhibited the highest adsorption capacity towards Orange II and the highest activity for the production of OH from H₂O₂ decomposition, which could be attributed to its high surface area and highly positively charged surface. However, FeCu exhibited the highest activity for the degradation of Orange II. The reason might be that FeCu has more unpaired electrons and higher redox ability, thus promoting the activation of adsorbed Orange II through the electron transfer process. By contrast, NiCu exhibited the highest activity for the removal of ciprofloxacin because ciprofloxacin was mainly degraded by OH. Finally, the main degradation intermediates of Orange II and ciprofloxacin were determined by liquid chromatography-mass spectrometry.

Reuse and recovery of raw hospital wastewater containing ofloxacin after photocatalytic treatment with nano graphene oxide magnetite

Inadequate treatment of hospital wastewater could result in considerable risks to public health due to its macro- and micropollutant content. In order to eliminate this problem, a new nanoparticle composite was produced under laboratory conditions and a photocatalytic degradation approach was used. Chemical oxygen demand (COD), biological oxygen demand (BOD₅), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), total phosphorus (TP) (macro) and oflaxin (micro) pollutant removal were investigated with the nano graphene oxide magnetite (Nano-GO/M) particles by two different processes, namely adsorption and photodegradation. Low removal efficiencies (21-60%) were obtained in the adsorption process for the parameters given above, after 90 min contact time at a pH of 7.8 with 5 g/L Nano-GO/M composite. Using the photodegradation process, higher removal efficiencies were obtained with 2 g/L Nano-GO/M composite for COD (88%), TSS (82%), TKN (95%) and oflaxin (97%), at pH 7.8 after 60 min irradiation time at a UV power of 300 W. The synthesized nanoparticle was reused for two sequential treatments of pharmaceutical wastewater with no significant losses of removal efficiencies (for oflaxin 97%-90%). The quality of the treated hospital wastewater was first class according to the Turkish Water Pollution Control Regulations criteria. This water could also be used for irrigation purposes.