Degradation Of Organic Wastewater Research Articles

Z-scheme heterojunction TNCoPc/BiOBr nanomicrospheres for efficient photodegradation of tetracycline and rhodamine B: Degradation performance, intrinsic mechanism and degradation pathway studies

The natural ecosystem has been significantly jeopardized due to the misuse of organic dyes and antibiotics. To treat organic wastewater safely and efficiently, this study synthesized a binary composite photocatalyst TNCoPc/BiOBr, using a solvothermal method that involved loading cobalt tetranitro phthalocyanine onto BiOBr. The results of the catalytic performance tests indicated that the composites exhibited the capacity to degrade rhodamine B and tetracycline hydrochloride by 97.75 % and 78.37 %, respectively. Moreover, the composite exhibited good cyclic stability. Subsequent analytical characterization confirmed the formation of a Z-scheme heterojunction, resulting in a synergistic effect. This Z-scheme heterojunction facilitated the capacity of photocatalyst to achieve enhanced light absorption, augmented photogenerated carrier separation efficiency, and augmented redox capacity. Additionally, theoretical calculations were employed to further elucidate the catalytic mechanism and synergistic effects. The results demonstrate that the Co-N4 sites are the active center of the TNCoPc and verify the contribution of nitro substitution to the photogenerated electron transfer mechanism on TNCoPc. Furthermore, a systematic degradation pathway was predicted and deduced based on Fukui indices and liquid chromatography-mass spectrometry data. This study presents a paradigm for the application of composite photocatalysts containing substituted phthalocyanines in the degradation of organic wastewater.

In-situ constructing oxygen-enriched vacancies BiOCl with 3D flower-structure for exceptional visible-light-driven photocatalytic properties

Bismuth oxychloride (BiOCl), emerging as a novel environmentally friendly nanomaterial, possesses considerable potential for photocatalytic degradation of organic wastewater. However, inadequate active sites and inhibited electron separation efficiency severely hinder its visible-light photocatalytic activity. To address this issue, herein we present a facile approach to in-situ construct BiOCl three-dimensional (3D) flower-structure (BOC-F) with oxygen-enriched vacancies for abundant active sites and effective electron separation efficiency through morphology control and vacancy engineering. The visible photocatalytic activity of BOC-F and BiOCl with 2D flaky-structure (BOC-S) was assessed through a systematic examination of the degradation efficiencies of tetracycline hydrochloride (TC-HCl) and rhodamine B (RhB). Under visible light irradiation, BOC-F exhibited superior visible photocatalytic activity, effectively degrading tetracycline hydrochloride (TC-HCl) (20 mg/L) and rhodamine B (RhB) (200 mg/L) within 90 min and 20 min of light exposure, respectively. The findings elucidate that BOC-F, possessing a 3D flower structure, manifests a heightened concentration of oxygen vacancies in contrast to BOC-S, consequently yielding excellent performance. Moreover, The ESR test showed that singlet oxygen (1O2) and hole (h+) were two main active species in the photocatalytic degradation of BOC-F. This work not only furnishes a facile method for constructing oxygen-rich vacancies in BiOCl but also provides fresh insights into the potential for enhancing the visible photocatalytic properties of Bi-based materials through vacancy engineering.

Preparation and photocatalytic mechanism of magnetic Ag2S/CoFe1.95Dy0.05O4 Z‐scheme heterojunction

AbstractThe synthesis of high‐efficiency magnetic composite photocatalyst by doping magnetic cobalt ferrite and compounding single semiconductor photocatalyst is a promising strategy to improve the oxidation ability of photocatalytic systems. In this paper, CoFe1.95Dy0.05O4 (CFDO) was prepared by doping Dy element into magnetic CoFe2O4, and Ag2S (AS)/CFDO with high‐efficiency magnetic photocatalyst was synthesized by compounding AS with CFDO as the substrate. The photocatalytic samples were characterized by different advanced characterization methods, and their photocatalytic degradation of methylene blue (MB) was studied. The results show that AS/CFDO exhibits higher visible light response, excellent photogenerated charge separation ability and migration efficiency, and excellent catalytic performance in the catalytic degradation system. The photocatalytic activity of AS/CFDO was the highest, and its photocatalytic degradation kinetic constant K was 2.48 and 1.54 times that of AS and CFDO, respectively. In addition, the catalyst contained in the catalytically contaminated solution can be effectively separated by an external magnetic field to achieve multiple cycles of degradation and recycling. The cyclic degradation experiments showed that AS/CFDO exhibited high degradation stability during the photodegradation process. After the fifth reuse, the degradation efficiency was still more than 88.0%. Finally, the possible photocatalytic mechanism of the samples was discussed. Therefore, this work provides an effective solution for the construction of photocatalysts with high efficiency, magnetic recovery, and cyclic degradation stability and avoids the secondary pollution of catalysts to organic wastewater. It is of great significance to create an environmentally friendly catalytic method for efficient cyclic degradation of organic wastewater.

Unveiling the roles of turbulence characteristics on the degradation of methylene blue by the activation of H2O2 through vortex-based hydrodynamic cavitation under neutral condition

Presently, fast degradation of organic wastewater has been achieved by the synergetic method of hydrodynamic cavitation and H2O2 at a laboratory scale, while the physico-chemical effect, especially the turbulence characteristics on the degradation process remains lacking. This paper presents investigation on the degradation of dyeing wastewater containing methylene blue (MB) under neutral condition, within a vortex-based hydrodynamic cavitation (VBHC) reactor. Operating conditions are firstly optimized and then used to collaborate with H2O2 to study the synergetic effects of this hybrid treatment method. The turbulence characteristics are subsequently obtained by a computational fluid dynamics (CFD) simulation, and the correlation between them and the degradation process of MB is revealed. The results indicate that the highest degradation rate of 91.95 % is achieved under optimal conditions. Higher inlet pressure (4.5 bar) owns the thickest vapor volume fraction, greatest vapor transfer rate, and largest size of cloud cavity in the vortex core region, indicating the strongest cavitation intensity; meanwhile, moderate solution temperature (30 ℃) also favors for the greatest cavitation intensity inside the reactor. The optimal cavitation intensity activates the considerable production of reactive oxygen species, and results in good consistency with the MB degradation performance, which predominately occurs in the annular region around the vortex rope. This research unveils the rationale behind the physical essences of the VBHC process and its influence on the degradation efficacy of MB, which can provide reliable guidance for further development of cavitational reactors to degrade organic pollutants by the VBHC/H2O2 hybrid treatment method.

A new strategy for clean utilization of zinc oxide dust: Preparation of spinel zinc ferrite by solid phase reaction and its catalytic degradation of organic wastewater

The resource utilization of zinc oxide dust (ZOD) is mainly focused on the efficient recovery of zinc by acid leaching at present. Because of a large amount of iron in ZOD and zinc components existing in multi-phase, the problems of low zinc recovery and the separation of zinc and iron ions in the leaching solution are unavoidable. Considering the characteristics of ZOD and the advantages of spinel zinc ferrite (ZnFe2O4) in the advanced oxidation degradation of organic wastewater, a new strategy for clean utilization of ZOD is proposed. The leaching efficiency of soluble zinc components in ZOD reached 96.7 % by selective dissolution with low concentration sulfuric acid solution, and the leaching solution without iron ions can be directly used for electrolytic zinc recovery. The insoluble components of zinc and iron in the leaching residue were converted into ZnFe2O4 by solid phase roasting. By adjusting the roasting temperature, time and molar ratio of Fe/Zn in roasting process, the proportion of zinc elements in the form of ZnFe2O4 reached 99.56 % and a single spinel zinc ferrite product was obtained. Zinc ferrite product activated by ball milling for 2 h (ZFO-2) showed very high catalytic activity in the treatment of organic wastewater by peroxonosulfate (PMS). In the presence of 1 mM PMS and 1 g/L ZFO-2 at 20 °C, the ZFO-2/PMS system achieved a removal rate of over 90 % within 40 min for wastewater containing RhB, MO and MG (10 mg/L). In addition, ZFO-2 is ferromagnetic and easily recovered by magnetic separation. The new strategy proposed in this paper takes into account the efficient recovery of soluble zinc components and the cooperative high-value utilization of insoluble components of zinc and iron in ZOD, which is a comprehensive utilization method with more sustainable resource allocation.

Bi-ZFO/BMO-Vo Z-scheme heterojunction photocatalysis-PMS bidirectionally enhanced coupling system for environmental remediation

Given the urgency of organic pollutant removal and the low efficiency of advanced oxidation processes (AOPs), a novel Bi-ZFO/BMO-Vo photocatalyst was fabricated via the solvothermal method. A coupling system was constructed to combine photocatalysis with peroxymonosulfate (PMS) oxidation processes, which synergistically degrade organic pollutants. Bi-ZFO/BMO-Vo exhibited excellent photocatalytic performance, which could remove 100 % RhB in 110 min and degrade 100 % MG in 70 min, and 88 % H-TC in 50 min. The excellent catalytic performance of Bi-ZFO/BMO-Vo was not only attributed to the synergistic effect of PMS activation and photocatalysis, but also attributed to the SPR effect of Bi nanoparticles, electron capture of oxygen vacancies, and intense contact of Bi-ZFO/BMO-Vo heterojunctions. The active species capture experiments and EPR tests indicated that 1O2, SO4–·, ·OH, and O2–· worked together for the RhB removal. The degradation intermediates of RhB were identified by LC-MS. Based on the experimental results, the band structure and Z-scheme charge transfer mechanism were proposed. Toxicity evaluation indicated that Bi-ZFO/BMO-Vo-Vis/PMS could significantly reduce RhB toxicity. This efficient and stable catalyst is expected to be used in organic wastewater degradation and practical applications.

A high-efficiency clay mineral based organic photocatalyst towards photodegradation of butyl xanthate in mineral processing wastewater

The organic solar cell active layer, well known for excellent visible light response capability, is regarded as a potential candidate for photocatalytic degradation of organic wastewater. However, the poor dispersibility in water due to its hydrophobicity property severely limited the degrading efficiency. In this work, a novel composite photocatalyst PM6:IDT8CN-M/CK2 with a broad visible absorption spectrum and non-toxicity was first synthesized through the intercalation compounding method. A good dispersibility of PM6:IDT8CN-M in wastewater was achieved with the help of rich interlamellar porosity and good hydrophilicity of calcined kaolin. This composite photocatalyst was successfully applied to the SBX photocatalytic degradation in mineral processing wastewater, and the SBX pollutants can be completely degraded within 10 min under the condition of visible light irradiation. Compared with other reported photocatalysts, the photocatalytic degradation efficiency of SBX was dramatically improved by at least seven times. Moreover, PM6:IDT8CN-M/CK2 has remarkable stability, sustaining degradation efficiencies of over 90 % in 60 cycles. Notably, the organic solar cell active layer in PM6:IDT8CN-M/CK2 can achieve carrier rapid separation and transport, enhancing the generation of active oxides (∙O2–, and ∙OH, etc.). At the same time, the large surface area of PM6:IDT8CN-M/CK2 provides a suitable environment for the oxidation reaction of active radicals with SBX to achieve this efficient photocatalytic degradation. Overall, this work not only extends the application scope of organic solar cell active layer, but also develops a high-efficiency SBX removal technique for the treatment of mineral processing wastewater.

Research progress of magnetic TiO2 photocatalyst in wastewater treatment

ABSTRACT TiO2 photocatalyst has the advantages of high catalytic activity, suitable energy band potential, high chemical stability, high photoelectric conversion efficiency, high safety and non-toxicity, which exhibits excellent performances in photocatalytic degradation of organic wastewater. However, it is difficult to separate and recover TiO2 photocatalyst from the reactive system. Interestingly, magnetic TiO2 prepared by combining TiO2 with superparamagnetic ferromagnetic particles can overcome this shortcoming. In this review, the preparation method and the photocatalytic mechanism of magnetic TiO2 were summarized. Moreover, the catalytic mechanisms of the modified binary, ternary and multicomponent magnetic TiO2 composite photocatalysts were compared, and the effects of different magnetic substrates on the degradation activity were discussed. Besides the applications in the wastewater treatment, the development trend and application prospects were prospected.

A novel ZnCo2O4/BiOBr p-n/Z-scheme heterojunction photocatalyst for enhancing photocatalytic activity.

In this study, we developed a novel p-n/Z-scheme heterojunction photocatalyst, ZnCo2O4/BiOBr (ZCo/BB), through a straightforward and safe hydrothermal-calcination-solvent thermal method. The composite photocatalyst demonstrated exceptional photocatalytic efficacy, particularly when the mass ratio of ZnCo2O4 was 25% (referred to as 25% ZCo/BB). Structural characterization and electrochemical analysis revealed that 25% ZCo/BB exhibited a larger specific surface area and a faster electron transfer rate. Under visible light exposure for 30min, methylene blue (MB) degradation reached 92%, and the reaction rate constants were 8.2 and 3.7 times higher than those observed for individual ZnCo2O4 and BiOBr, respectively. Furthermore, the 25% ZCo/BB demonstrated exceptional photocatalytic stability over four cycles, maintaining over 80% MB degradation after each cycle. The outstanding photocatalytic activity was attributed to the p-n/Z-scheme heterojunction construction, which promoted charge separation and inhibited carrier recombination. In addition, ·OH and h+ were the major active species in photocatalysis, and · was identified as a secondary active species. This work presents an efficient heterojunction photocatalyst for the degradation of organic wastewater.

Progress of organic wastewater degradation by atmospheric pressure gliding arc plasma technology: A review

The prevention and treatment of organic pollutants in wastewater have attracted extensive attention because they threaten ecological balance and human health. Traditional wastewater treatment technologies, such as physical, chemical, biological methods, etc., are still limiting and challenging due to some factors, such as high energy consumption, chemical agents, low efficiency, and secondary pollution. At present, gliding arc plasma, based on equilibrium/non-equilibrium in plasma temperature, demonstrates itself to be one of the most promising technologies for the degradation of refractory organics with its fast degradation rates, no secondary contamination, high efficiency, and so on. The theoretical mechanisms and typical applications of gliding arc plasma degradation of wastewater are introduced in detail in this paper. The physical and chemical characteristics of gliding arc plasma and the role of the reactive species in the plasma are reviewed.

Preparation of SrFe12O19/SiO2/TiO2 Photocatalysts and Degradation of Methylene Blue and Petroleum Wastewater

AbstractThe synthesis and application of magnetic photocatalysts have become a critical topic in organic waste treatment. In this study, SrFe12O19 powder, SrFe12O19/SiO2 particles and SrFe12O19/SiO2/TiO2 photocatalysts were successfully produced using coprecipitation technique, Stöber process and solvothermal method, respectively. The degradation of methylene blue dye and simulated petroleum wastewater under simulated sunlight and ultraviolet light was used to assess the photocatalytic activity of the SrFe12O19/SiO2/TiO2 composites. Results showed the high photocatalytic performance of the produced SrFe12O19/SiO2/TiO2 photocatalysts with a 1 : 4 mass ratio of SrFe12O19 to TiO2 synthesized at 170 °C, whose surface has more hydroxyl groups as the active center. At 120 min of irradiation, the photodegradation rates of methylene blue and simulated petroleum wastewater were 83.94 % and 60.77 %, respectively. The photocatalytic activity of the Fe12O19/SiO2/TiO2 with ferrite semiconductor/insulator/semiconductor structure was improved by the action of the magnetic field of SrFe12O19. The SrFe12O19/SiO2/TiO2 composite particles can be recycled easily under an external magnetic field and show good application prospects in organic wastewater degradation.

A novel Ag2O/Bi2WO6 composite with enhanced piezocatalytic performance for ciprofloxacin removal

Bi2WO6, an important semiconductor material, has been widely used in the catalytic degradation of organic wastewater in recent years. However, Bi2WO6 owns the low band gap energy, the recombination of the produced e−-h+ pairs expected to be fast, which leads to undesirable degradation effects. In order to improve its piezocatalytic ability, this paper combined the semiconductor material Bi2WO6 with Ag2O to form Ag2O/Bi2WO6 piezoelectric catalysts, which was characterized and its removal effect on ciprofloxacin (CIP) was discussed. According to the analyses, the reaction rate constant for the piezocatalytic removal of CIP in the company of 5 % composite ratio of Ag2O/Bi2WO6 was about 1.40 and 4.87 times higher than it was when Bi2WO6 and piezocatalytic technology were used alone. By exploring the experimental principle, the increased piezocatalytic activity of Ag2O/Bi2WO6 was found to be due to the creation of Z-scheme heterojunction, which could efficiently separate the e−-h+ pairs. Reuse experiments were also carried out, and the results showed that it has good reusability and stability in piezocatalysis. In summary, Ag2O/Bi2WO6 has good piezocatalytic activity for the removal of CIP.

Synthesis of novel maghemite (γ-Fe2O3)-decorated g-C3N4 nano-tubes (g-C3N4 NTs/γ-Fe2O3) photocatalytic nano-composite for ultrafast degradation of organics in wastewater: Insight into the mechanism of photoexcited charge separation

In this study, to enhance the photodegradation of organic pollutants including Methyl blue (MB) and Methyl orange (MO), mesoporous tubular g-C3N4/γ-Fe2O3 (FCN) nano-composite synthesized via facile procedures. FT-IR and XRD data proved the existence of maghemite (γ-Fe2O3) nanoparticles on the g-C3N4 nano-tubes. Experimental data showed that among fabricated photocatalysts, FCN exhibited the highest activity rate toward the photodegradation of MB (%96.1/60 min) and MO (%98.3/120 min) with an excellent kinetic rate of 0.0509 min−1 (MB) and 0.0352 min−1 (MO) under visible light and considerable photocatalytic stability after six cycles. In addition, the visible light-harvesting-capability of FCN enhanced compared to unequipped forms of g-C3N4 (BCN and CNNTs), surprisingly functioning under irradiation of photons greater than 900 nm, proving the synergistic role of γ-Fe2O3 nanoparticles not only in harvesting visible light but also in hindering electron-hole recombination. BET analysis showed mesoporous structure, the highest SSA and pore volume (55.623 m2/g, 0.1699 cm3/g) for FCN, indicating more active sites and enhanced target molecules adsorption, then augmented photocatalytic performance in comparison to the rest of the samples. Finally, FCN generated an excellent photocurrent density (3.76 μA/cm2) with the least arc radius, introducing a high-potential hybrid photocatalyst to the research field.

Organic Wastewater Treatment using Two-dimensional Graphene-based Photocatalysts: A Review

Photocatalysts have gained enormous attention in water decontamination due to their economic viable and intriguing properties. Recently, graphene-based semiconductors have become the sparkling star on the horizon of material science. The coupling of two-dimensional graphene and its derivatives (graphene oxide and reduced graphene oxide) with semiconductors could effectively enhance the efficiency in organic wastewater degradation under light irradiation. Hence, a collective study on this topic is necessary. Four types of graphene-based semiconductors, viz. titania, zinc oxide, cadmium sulfide, and bismuth oxychloride, are explored. Besides, synthesis approaches and properties of these photocatalysts are elucidated too. We hope this review could enable us to rationally design and harness the morphology, structure and electronic properties of these advanced materials. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

B4C/Ce co-modified Ti/PbO2 dimensionally stable anode: Facile one-step electrodeposition preparation and highly efficient electrocatalytic degradation of tetracycline

The application of PbO2 for electrochemical oxidation technology is limited by its low electrocatalytic activity and short service life. Herein, based on the facile one-step electrodeposition, we prepared a boron carbide (B4C) and cerium (Ce) co-modified Ti/PbO2 (Ti/PbO2–B4C–Ce) electrode to overcome these shortcomings. Compared with Ti/PbO2 electrode, the denser surface is displayed by Ti/PbO2–B4C–Ce electrode. Meanwhile, electrochemical characterization indicates that the introduction of B4C and Ce significantly enhance the electrochemical performance of PbO2 electrode. In degradation experiments, under optimized conditions (current density 20 mA cm−2, pH 9, 0.15 M Na2SO4 and 30 °C), the fully degradation of tetracycline (TC) can be completed within 30 min. Furthermore, the trapping experiment demonstrates that ∙OH and SO4·- radicals have a synergistic effect in the degradation process of TC. Based on results of liquid chromatography-mass spectrometer, the generated ·OH preferentially attacks amides, phenols and conjugated double bond groups in TC. Importantly, Ti/PbO2–B4C–Ce electrode maintains a constant degradation efficiency even after 10 recycling tests, and its service life is 2.4 times of traditional Ti/PbO2 electrode. Hence, Ti/PbO2–B4C–Ce electrode is a promising electrode for degradation of organic wastewater containing amides, phenols, and conjugated double bond groups.

Adsorption and Degradation of Organics in Wastewater on Municipal Sludge.

Adsorption and degradation of organic compounds on sludge were investigated by comparing activated and inactivated sludge at various dosages, pH values, and temperatures. The organic compounds in wastewater were identified and evaluated through fluorescence spectra. The results show that optimum adsorption occurred as the activated and inactivated sludge concentration was 4000 mg/L at a pH of 7.99 and a temperature of 30 °C. The fluorescence scanning spectrum indicated that activated sludge could remove protein-like organic matter, fulvic acid-like organic matter, and humic acid-like organic matter by 22.1, 9.4, and 41.2%, respectively, via adsorption only or by 25.9, 9.8, and 74.3%, respectively, via adsorption and degradation. Under optimum conditions, by using the good adsorption performance of sludge combined with other sewage treatment technologies, the treatment of high-content organic wastewater can be achieved.

Dual-functional MnS2/MnO2 heterostructure catalyst for efficient acidic hydrogen evolution reaction and assisted degradation of organic wastewater

The design and synthesis of non-precious metal dual-functional electrocatalysts through the modulation of electronic structure are important for the development of renewable hydrogen energy. Herein, MnS2/MnO2-CC heterostructure dual-functional catalysts with ultrathin nanosheets were prepared by a two-step electrodeposition method for efficient acidic hydrogen evolution reaction (HER) and degradation of organic wastewater (such as methylene blue (MB)). The electronic structure of Mn atoms at the MnS2/MnO2-CC heterostructure interface is reconfigured under the joint action of S and O atoms. Theoretical calculations show that the Mn d-band electron distribution in MnS2/MnO2-CC catalyst has higher occupied states near the Fermi level compared to the MnO2 and MnS2 catalysts, which indicates that MnS2/MnO2-CC catalyst has better electron transfer capability and catalytic activity. The MnS2/MnO2-CC catalysts require overpotential of only 66 and 116 mV to reach current density of 10 and 100 mA cm−2 in MB/H2SO4 media. The MnS2/MnO2-CC catalyst also has a low Tafel slope (26.72 mV dec−1) and excellent stability (the performance does not decay after 20 h of testing). In addition, the MB removal efficiency of the MnS2/MnO2-CC catalyst with a better kinetic rate (0.0226) can reach 97.76%, which is much higher than that of the MnOx-CC catalyst (72.10%). This strategy provides a new way to develop efficient and stable non-precious metal dual-functional electrocatalysts for HER and organic wastewater degradation.

Cyclic catalytic Fe-N doped composite particle electrodes derived from gasification fine slag for non-selective mineralization of organic wastewater

As a typical coal-based solid waste, coal gasification fine slag (GFS) will have an annual discharge of more than 50 million tons in 2025 in China alone. However, the difficulty of its resource utilization lies in the precise separation of carbon and ash due to their complex distribution pattern. There is an urgent need to develop GFS-based materials for comprehensive utilization of carbon and ash. In this study, a combined process of acid leaching and pyrolysis was designed, in which active metal iron was leached from ash and immobilized on the surface of residual carbon in the form of Fe-N-C. The unique structure of Fe-N doped carbon/ash synergistically improved the efficiency of electrocatalytic degradation of organic wastewater by 72.78 ± 1.37%. The hierarchical porous structure of residual carbon considerably enhanced the accessibility of ash catalytic sites. Abundant ash defects and Fe-N active sites promoted the conversion of free radical precursors to reactive oxygen species (ROS). The removal rate of various organic wastewater within 35 min reached more than 100 ± 1.83% %, with excellent electrocatalytic performance and pH adaptability. Fe-NCPE had a high specific surface area (318.36 m2·g−1), orderly graphite phase (002 crystal surface size 1.3 nm), and abundant catalytic sites. We also proposed the catalytic mechanism by combining molecular simulation with experiments. The high adsorption capacity above 24.07 ± 0.12 mg·g−1 ensured the continuous and rapid supply of pollutants and H2O2 near the catalytic site·H2O2 was converted into ROS mainly composed of hydroxyl groups through the valence state change of aluminum or Fenton-like reaction of nitrogen-linked iron. The ROS then attacked organic molecules to degrade pollutants. The above two processes corresponded to two cyclic catalytic reactions. Therefore, this study provides an innovative and promising approach for comprehensive utilization of carbon and ash in GFS.

Mn-SR as an ozone catalyst for coal to ethylene glycol organic wastewater treatment: Activity evaluation and reaction mechanism

Large amounts of soda residue waste from the production of sodium carbonate industries cause serious pollution to environment. In this study, a novel Mn-SR non-homogeneous ozone catalyst was prepared by mixed calcination method using soda residue as the main component for organics degradation of coal to ethylene glycol wastewater. Firstly, under the optimal Mn-SR preparation process (95% n-SR (msoda residue: mkaolin = 8:1), 5% MnO2, calcination temperature: 500 °C, calcination time: 4 h) and the optimal operating conditions (pH: 8, water temperature: 40 °C, catalyst dosage: 320 g/L, O3 dosage: 20 g/L) for the reaction of 60 min, the COD removal rate reaches to 77.1%, which is 63.9% higher than only ozonation COD removal efficiency under the same conditions. Kinetic study shows that water temperature is the most important factor affecting COD degradation rate in the reaction system. Through the adsorption performance, ozone utilization, free radical quenching experiments and three-dimensional fluorescence tests, the catalytic performance of Mn-SR catalysts for ozonation was investigated. The results showed that Ca and Mg in Mn-SR play a major role in organics degradation, while MnO2 plays a complementary role in the degradation of high COD concentrations. It was confirmed that hydroxyl radicals (·OH) are the main reactive radicals in the Mn-SR catalytic ozonation system, which plays an important role in the degradation of organics in wastewater. Meanwhile, after Mn-SR was reused and regenerated for five times, the COD removal rates was still higher than 67.0%, and Mn-SR recovery rates were more than 94.7%, which showed a good stability.

Efficient degradation of tetracycline: Performance and mechanism study of Fe3O4@CF composite electrode materials applied to a non-homogeneous photo-electro-Fenton process

In order to improve the low conversion efficiency of Fe2+ in conventional electro-Fenton, this work developed solvent-heated Fe3O4@carbon felt (Fe3O4@CF) electrodes, which have good photo-electrochemical characteristics. The structure, composition and photoelectrochemical properties of the electrode were analyzed by a series of characterization measurements. The loading of Fe3O4 on the carbon felt (CF) surface improves the agglomeration of Fe3O4, effectively increasing the active sites of the electrode reaction and also improving the photoelectrochemical properties of the electrode. The Fe3O4@CF electrode was applied to the photo-Fenton, electro-Fenton and non-homogeneous photo-electro-Fenton systems respectively, and the results showed that after 60 min reaction, the best tetracycline removal efficiency of Fe3O4@CF electrode in heterogeneous photo-electro-Fenton system is 97.8 %. Then, the influencing factors in the degradation of tetracycline in the non-homogeneous photo-electro-Fenton system were investigated. Fe3O4@CF electrode had good cycling stability as the removal rate of tetracycline in solution was still above 85 % after 5 cycles of stabilization experiments. Fe3O4@CF electrode had good mineralization effect and the removal rate of TOC in solution could reach 83.3 %. Finally, free radical quenching experiments were conducted to identify the active substances that play a major role in the reaction process, and the reaction mechanism of the non-homogeneous photo-electro-Fenton system for the degradation of tetracycline was proposed. In summary, it is shown that Fe3O4@CF electrode is of great significance for the application of non-homogeneous photo-electro-Fenton system for the degradation of organic wastewater.