Total Organic Carbon Removal Rate Research Articles

Preparation of a rice straw-based green separation layer for efficient and persistent oil-in-water emulsion separation

Inefficiency, high cost, and complex operation have emerged as shackles for large-scale separate oil-in-water emulsion. Herein, a low-cost and eco-friendly separation layer with a rough structure and rich anionic groups was fabricated from rice straw (RS) via a simple acid-base treatment and slight squeeze process. The separation layer’s morphology, composition, and wettability were investigated. It was then employed to separate oil-in-water emulsion. The RS after acid and alkali treatment (A1A2-RS) exhibited a clear fiber structure and abundant humps, which made the separation layer superwettable and highly electronegative (−26.55 mV). The overlapped and intertwined A1A2-RS layer structure owned a superior performance for hexadecyl-trimethyl-ammonium-bromide (CTAB) adsorption and tiny oil interception. As a result, the separation layer had stable fluxes (>500 LMH) for multiple CTAB-stabilized emulsions and the obtained filtrates performed low total organic carbon (TOC) contents (<30 mg/L). In addition, the A1A2-RS layer had excellent renewability (10 cycles/ 200 mL) and the flux could be substantially recovered merely by aqueous wash. Moreover, filtrate analysis showed that the A1A2-RS layer had a good effect on actual emulsion treatment with a TOC removal rate of 89.56%.

Electrochemically reduced phytic acid-doped TiO2 nanotubes for the efficient electrochemical degradation of toxic pollutants

Element-doped TiO2 nanotube arrays (TNAs) with optimized active sites provide an effective approach for significantly improving electrocatalytic performance. The challenges in such construction mainly include selection of green dopant and control of active sites. Herein, we present phytic acid as a phosphorus source for P-doped TNAs. An oxygen vacancy (Ov) and P co-doped TNAs (P-TiO2−y) was prepared as an electrochemical oxidation anode. P-TiO2−y exhibits excellent degradation activity due to the formation of Ti-O-P bonds and generation of Ov. P-doping was beneficial in improving the oxygen evolution potential of the electrode, which would be benefit for electrocatalytic degradation of pollutants. Using the P-TiO2−y anode with a current density of 10 mA/cm2 for tetracycline degradation, after a 3 h treatment, the removal rate, chemical oxygen demand and total organic carbon removal rates were 100%, 90.32% and 76.60%, respectively. The P-TiO2−y also has excellent degradation performance for phenol, hydroquinone, p-nitrophenol and metronidazole.

Treatment of agrochemical wastewater by thermally activated persulfate oxidation method: Evaluation of energy and reagent consumption

Agrochemical wastewater is a potential danger to public health, the environment, and other livings, as it contains hazardous compounds that can harm plants and animals and cause many diseases in humans. In this work, the thermally activated persulfate (TAP) oxidation method, which is an effective and practical approach for degradation of agrochemical wastewater, was carried out. Optimization and modeling of total organic carbon (TOC) and decolorization of the agrochemical wastewater were studied using a central composite design. Persulfate was thermally activated and the effect of the temperature, treatment time, and persulfate concentration on the TAP method was detailed. Temperature and persulfate concentration were the most effective process parameters for TOC removal. Results, model coefficients, and analysis of variance (ANOVA) showed that the resulting model was precise and acceptable for predicting TOC and color removals. The feasibility of energy and reagent consumption was proposed. Under conditions where TOC and color removal rates were reached 70.2% and 100%, the electrical energy and persulfate consumption were 529.5 kWhm−3 and 21.6 kgm−3, respectively. Chemical composition analysis of wastewater and treated samples showed that the TAP method was able to degrade almost all compounds found in this study, including those resistant to oxidation. Ion chromatography analysis showed that the ion concentration of the wastewater samples changes with the applied temperature and the oxidant concentration.

Effect of Fe-based catalytic ozonation and sole ozonation on the characteristics and conversion of organic fractions in bio-treated industrial wastewater

The conversion of hydrophobic (HPO)/transphilic (TPI)/hydrophilic (HPI) fractions of dissolved effluent organic matter (EfOM) in water by sole ozonation process (SOP) and catalytic ozonation process (COP) were investigated in this study. The modified iron shavings were used as catalyst in COP. The difference in total organic carbon (TOC) removal rate between SOP and COP for two types of bio-treated industrial wastewater was mainly caused by the different HPI degradation degree. The accumulation of HPI in SOP was 28.8% (in bio-treated dyeing wastewater) and 88.8% (in bio-treated paper-making wastewater) higher than that in COP, while HPO was degraded by more than 90% in both processes. Part of HPO was converted to TPI in the early stage (0–15 min) and the original HPI in the raw water was degraded at the same time. In the middle stage (15–60 min), TPI was transformed into HPI. The remaining fluorescent substances in HPI fraction in SOP were higher than those in COP, indicating that more HPI was accumulated in SOP. Among the fluorescent substances, aromatic protein II and SMP-like substances were removed more completely, while humic acid-like substances were relatively more difficult to degrade. Furthermore, COP had higher removal for fulvic acid-like substances, SMP-like substances and humic acid-like substances than SOP, while the removals of aromatic protein by COP and SOP were almost the same. COP had better removal effect than SOP for TPI and HPI organic pollutants with molecular weight (MW) more than 2 kDa. SOP and COP had no significant difference in the removal of HPO fraction and small molecular organics with MW less than 2 kDa. The remaining organic pollutants in the effluent of COP was mainly hydrophilic small molecular substances, which would be benefit for secondary biochemical process.

Design, preparation, characterization, and application of MnxCu1-xOy/γ-Al2O3 catalysts in ozonation to achieve simultaneous organic carbon and nitrogen removal in pyridine wastewater

In the process of treating high-concentration pyridine wastewater, problems such as low treatment efficiency and total nitrogen (TN) residues are always encountered. Catalytic ozonation can degrade pyridine wastewater well, and it also has the potential to remove TN. However, limited research has been conducted on the development of ozonation catalysts that can simultaneously remove the total organic carbon (TOC) and TN. Density functional theory (DFT) technology can determine the number of active components on the catalyst based on its composition; therefore, it can be used to guide the research and development of such catalysts. Here, we presented a strategy to guide the preparation of two-component Mn and Cu catalysts using DFT technology. By characterising and applying the prepared MnxCu1-xOy/γ-Al2O3 catalysts, it was confirmed that the DFT accurately predicted the changes in the active site content. The selected catalyst also achieved strong TOC and TN removal rates during the catalytic ozonation of high-concentration pyridine wastewater. A Box-Behnken design and response surface methodology was used to optimise the process conditions of catalytic ozonation and verify its stability. Under the optimal reaction conditions, the TOC and TN removal efficiencies from a 500 mg/L pyridine solution were 99.8% and 45.8%, respectively. This work indicated that the use of DFT for the design of catalytic materials was an effective method, which can provide a theoretical basis for material design and reduce the time for material screening.

Highly-crystalline Triazine-PDI Polymer with an Enhanced Built-in Electric Field for Full-Spectrum Photocatalytic Phenol Mineralization

Herein, a conjugated triazine-perylene diimide (triazine-PDI) polymer photocatalyst is prepared, and its full-spectrum photo-oxidative activity is evaluated. Enhanced dipole promotes the generation and separation of photo-induced charges, while its high degree of crystallinity results in a strong built-in electric field, which provides channels for the rapid transfer of the photo-generated charges. The advantageous structural characteristics enable a phenol degradation rate constant of 0.191 h−1, which is which is 12.7 and 2.2 times greater than bulk g-C3N4 and supramolecular PDI, respectively. Besides, triazine-PDI’s deep VB position led to a high rate of mineralization, i.e., a 79% total organic carbon removal rate in 24 h, which is 38% higher than that of self-assembled PDI. In summary, this work demonstrates the critical influence of crystallinity and built-in electric field adjustments for PDI photocatalytic activity.

Effects of pure oxygen aeration on organic pollutants removal performance and soluble microbial products characteristics of salt-tolerant activated sludge

ABSTRACT The effects of pure oxygen aeration on organic pollutants removal performance and effluent soluble microbial products (SMP) characteristics of salt-tolerant sludge for the treatment of wastewater with the salinity from 1.0% to 3.5% were investigated. The results showed that the oxygen transfer efficiency of the pure oxygen aeration was higher than that of the air aeration. At the low salinities (0.5%, 1.0%, 1.5%), the total organic carbon (TOC) removal rates were 71.42%, 72.88% and 76.30%, respectively, much higher than those with air aeration. However, there were no significant differences of TOC removal efficiency between the air aeration and the pure oxygen aeration at high salinities (2.5% and 3.5%). The SMP contents showed a trend of first decline and then increase generally. The content of SMP with pure oxygen aeration was lower than that with air aeration at low salinity, whereas an opposite result was obtained for salinity above 2.5%. Five excitation–emission matrix (EEM) fluorescence peaks detected in the SMP with pure oxygen aeration and air aeration were assigned to tryptophan protein-like, tyrosine protein-like and humic acid-like substances. Humic acid-like fluorescence mainly appeared in the SMP with air aeration, which may be due to respiratory failure under air aeration conditions.

Degradation of aqueous bisphenol A in the CoCN/Vis/PMS system: Catalyst design, reaction kinetic and mechanism analysis

Low levels of pharmaceutical and personal care products (PPCPs) in the environment have attracted widespread attention as a new class of organic pollutants. Degradation of these PPCPs by optimizing advanced oxidation processes (AOPs) is highly desirable, but remains a huge challenge. Here, the Co sites embedded in carbon nitride catalyst (CoCN) was synthesized by a simple one-step pyrolysis of Co-based Zeolitic Imidazolate Framework-67 (ZIF-67) and melamine, of which highly dispersed Co atom sites were uniformly doped in the CN ring of g-C3N4. In the optimized system of visible light irradiation involving CoCN and peroxymonosulfate (CoCN/Vis/PMS system) (λ ≥ 420 nm, [PMS] = 0.2 g L-1, pH = 7.0), 100% of bisphenol A (BPA, 20 mg L-1) was removed after 2 min and the total organic carbon (TOC) removal rate of BPA reached 88.8% after 90 min reaction. Detailed characterization showed that a specially designed unique Co-N bond structure was crucial for the high degradation performance of BPA in the CoCN/Vis/PMS system. HO∙, SO4∙-, O2∙-, h+ and 1O2 contributed to the BPA degradation in the CoCN/Vis/PMS system. Besides, the effect of solution pH and several common anions in environmental water on BPA removal was evaluated. Several typical pollutants, sulfamethoxazole (SMX), ciprofloxacin (CIP), 4-chlorophenol (4-CP) and atrazine (ATZ), were effectively degraded by the same CoCN/Vis/PMS system, which exhibited universal applicability of this AOP reaction. The cycling degradation experiment showed the stability and reusability of the CoCN/Vis/PMS system. This work offers immense hope to the environmental purification and provides numerous new opportunities for the effective removal of other pollutants beyond BPA, SMX, CIP, 4-CP and ATZ.

Highly efficient removal of amoxicillin from water by three-dimensional electrode system within granular activated carbon as particle electrode

Amoxicillin (AMX) is a widely used broad-spectrum antibiotic. In this study, a three-dimensional electrode system (3DES) was constructed with granular activated carbon (GAC) packed between the anode and cathode electrodes to degrade AMX. Under optimal conditions of 3DES (current density of 5 mA/cm2, 17 mM NaCl as the electrolyte, an initial pH of 5.56, and a GAC-quartz sand volume ratio of 9:1), the removal efficiency of AMX reached 98.98 % after 2 h of treatment. It was also shown that the total organic carbon (TOC) removal efficiency (R) and reaction rate constant (k) of 3DES were 47.6 % and 0.22 h−1, respectively, much higher than the sum of the two-dimensional electrode system (2DES) and adsorption process (30.7 % and 0.12 h−1). Thus, there existed the synergy between electrolysis and adsorption in 3DES, which enhanced the TOC removal efficiency and removal rate by up to 35.5 % and 46.8 %, respectively. Electrochemical characterization was explored using an electrochemical workstation. It demonstrated that GAC played an important role in reducing the mass transfer resistance, and the mass transfer rate of 3DES was 2.24 times that of the 2DES. It was also deduced that AMX adsorbed on the surface of GAC directly participated in the electrochemical oxidation to achieve the in-situ regeneration of activated carbon. The results of Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) of GAC verified it again. In summary, 3DES has good electrochemical performance, and it is an efficient, cost-effective, and environmentally friendly system for AMX degradation.

Degradation of Auramine-O in Aqueous Solution by Ti/PbO2-Electro-Fenton Process by Hydrogen Peroxide Produced In Situ

Electrochemical removal of synthesis solution containing 50 mg/L auramine-O through Ti/PbO2 electrodes and carbon felt air-diffusion electrode to in situ generate hydrogen peroxide (H2O2) by the oxygen (O2) reduction. The effects of operating conditions, FeSO4·7H2O concentrations, current density, initial concentration, initial pH value and sodium sulfate (Na2SO4) concentration were investigated. For reaction of 60 min, the auramine-O removal rate reached 99% and total organic carbon (TOC) removal rate was close to 64.27%. This means that the organic macromolecules in the pollutants have been completely destroyed and broken down. The degradation of auramine-O under electro-Fenton (EF) process using Ti/PbO2-carbon felt was analyzed from the dimensions of TOC, mineralization current efficiency, energy consumption, degradation mechanism and kinetics. Comparing EF-Ti/PbO2 with Ti/PbO2 anode, AO (anodic oxidation)-Ti/PbO2 anodic oxidation using Ti/PbO2 anode and EF-Pt EF process with Pt anode, the consequences demonstrated that Ti/PbO2-EF process by hydrogen peroxide produced in situ was the best choice than others.

Trace Ti3+- and N-codoped TiO2 nanotube array anode for significantly enhanced electrocatalytic degradation of tetracycline and metronidazole

A trace Ti3+- and N-codoped TiO2 nanotube array (TiON) anode is fabricated by electrochemical reduction after introducing nitrogen into the TiON. The TiON anode material is characterized by scanning electron microscopy, X-ray diffraction, Raman spectra and X-ray photoelectron spectroscopy. Electrochemical analyses of TiON, including cyclic voltammetry, electrochemical impedance spectroscopy and linear scan voltammetry, are conducted to confirm that the electrochemical performance could be significantly improved by electrochemical reduction and N doping. The achieved TiON anode is applied to the electrocatalytic oxidation of tetracycline (TC) and metronidazole (MNZ). The effect of applied current density, initial solution pH and initial TC/MNZ concentration on the reaction kinetics is systematically evaluated to obtain the optimal conditions. The degradation processes follow an apparent first-order kinetic model in all conditions. After 240 min of reaction time, the TC removal efficiency, chemical oxygen demand (COD) removal rate and total organic carbon (TOC) removal rate are >99%, 92.86% and 74.98%, respectively. The MNZ removal efficiency, COD and TOC removal rate achieved are >99%, 93.03% and 79.30%, respectively, after 240 min of degradation. The excellent removal efficiency of TC and MNZ indicates that this TiON anode is a promising material in the practical application of removing antibiotics from water.

Heterogeneous catalytic oxidation degradation of BPAF by peroxymonosulfate active with manganic manganous oxide: Mineralization, mechanism and degradation pathways

In this study, the catalytic ability and mechanisms involved in activating peroxymonosulfate (PMS) with Mn3O4 and the degradation pathways of bisphenol-AF (BPAF) removal was investigated. SO4−• and ·OH which were explored by and scavenging tests were the major reactive radicals in the Mn3O4/PMS system. A simple simulation algorithm was also used to calculate the relative concentrations of SO4−• ([SO4−•]) and ·OH ([·OH]) which were 8.39 × 10 −15 M and 6.96 × 10 −13 M, respectively. The mechanism for the electron transfer between the Mn (II) and Mn (III) species was discussed. Three degradation pathways of BPAF were determined by the GC/MS and LC/MS technology, including chemical mechanism of oxidation, hydroxylation, electron transfer, polymerization, and ring-cleavage. In addition, the results suggested that the Mn3O4/PMS system had an efficient total organic carbon (TOC) removal rate and excellent environmental adaptability, the removal rate of TOC being as high as 73.2% in the control condition. Furthermore, the reuse experiments and the comparison on the structural and componential changes of Mn3O4 powder before and after reaction demonstrated that the Mn3O4 catalyst possessed excellent stability and reusability. Finally, a maximum BPAF degradation of approximately 90.0% was achieved on the optimal conditions for 500 mg/L Mn3O4 dosage, 4 mM PMS concentration, 7.0 ± 0.2 initial pH, and 5 mg/L BPAF concentration respectively. And the effect of the coexisting anions and natural environmental water quality were also considered. This study demonstrated the Mn3O4/PMS system can be considered as a green approach for the removal of environmental reluctant pollutants.

Effective treatment of levofloxacin wastewater by an electro-Fenton process with hydrothermal-activated graphite felt as cathode

The performance of the cathode significantly affects the ability of the electro-Fenton (EF) process to degrade chemicals. In this study, a simple method to modify the graphite felt (GF) cathode was proposed, i.e. oxidizing GF by hydrothermal treatment in nitric acid. The surface physical and electrochemical properties of modified graphite felt were characterized by several techniques: scanning electron microscope (SEM), water contact angle, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and linear scanning voltammetry (LSV). Compared with an unmodified GF (GF-0), the oxygen reduction reaction (ORR) activity of a modified GF was significantly improved due to the introduction of more oxygen-containing functional groups (OGs). Furthermore, the results showed that GF was optimally modified after 9 h (GF-9) of treatment. As an example, the H2O2 generation by GF-9 was 2.26 times higher than that of GF-0. After optimizing the process parameters, which include the initial Fe2+ concentration and current density, the apparent degradation rate constant of levofloxacin (LEV) could reach as high as 0.40 min−1. Moreover, the total organic carbon (TOC) removal rate and mineralization current efficiency (MCE) of the modified cathode were much higher than that of the GF-0. Conclusively, GF-9 is a promising cathode for the future development in organic pollutant removal via EF.

Photocatalytic degradation efficiency of hazardous macrolide compounds using an external UV-light irradiation slurry reactor.

The current work investigates the removal of two hazardous macrolide molecules, spiramycin and tylosin, by photodegradation under external UV-light irradiation conditions in a slurry photoreactor using titanium dioxide as a catalyst. The kinetics of degradation and effects of main process parameters such as catalyst dosage, initial macrolide concentration, light intensity and stirring rate on the degradation rate of pollutants have been examined in detail in order to obtain the optimum operational conditions. It was found that the process followed a pseudo first-order kinetics according to the Langmuir-Hinshelwood model. The optimum conditions for the degradation of spiramycin and tylosin were low compound concentration, 1 g L-1 of catalyst dosage, 100 W m-2 light intensity and 560 rpm stirring rate. Then, a maximum removal (more than 90%) was obtained after 300 min of irradiation time. Furthermore, results show that the selection of optimized operational parameters leads to satisfactory total organic carbon removal rate (up to 51%) and biochemical oxygen demand to chemical oxygen demand ratio (∼1) confirming the good potential of this technique to remove complex macrolides from aqueous solutions.

Bi-Polymer Electrospun Nanofibers Embedding Ag3PO4/P25 Composite for Efficient Photocatalytic Degradation and Anti-Microbial Activity

Using a bi-polymer system comprising of transparent poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) (PVP), a visible light active Ag3PO4/P25 composite was immobilized into the mats of polymeric electrospun nanofibers. After nanofibers synthesis, sacrificial PVP was removed, leaving behind rough surface nanofibers with easy access to Ag3PO4/P25 composite. The remarkable photocatalytic efficiency was attained using a PMMA and Ag3PO4/P25 weight ratio of 1:0.6. Methyl orange (MO) was used to visualize pollutant removal and exhibited stable removal kinetics up to five consecutive cycles under simulated daylight. Also, these polymeric nanofibers (NFs) revealed an important role in the destruction of microorganisms (E. coli), signifying their potential in water purification. A thin film fibrous mat was also used in a small bench scale plug flow reactor (PFR) for polishing of synthetic secondary effluent and the effects of inorganic salts were studied upon photocatalytic degradation in terms of total organic carbon (TOC) and turbidity removal. Lower flow rate (5 mL/h) resulted in maximum TOC and turbidity removal rates of 86% and 50%, respectively. Accordingly, effective Ag3PO4/P25 immobilization into an ideal support material and selectivity towards target pollutants could both enhance the efficiency of photocatalytic process under solar radiations without massive energy input.

Biological treatment of non-biodegradable azo-dye enhanced by zero-valent iron (ZVI) pre-treatment

Zero-valent iron (ZVI) pre-treatment in sequential strategy for removal of non-biodegradable azo-dye Orange II by activated-sludge was quantitatively examined. The decolorization and TOC (total organic carbon) removal of Orange II by ZVI pre-treatment were examined in the ranges of pH from 3 to 11 and ZVI dosage from 500 to 2000 mgL−1. While the decolorization was enhanced with decreasing pH and the optimal pH for decolorization was found at pH 3, the TOC removal rate at pH 3 remained at 22.2% and the maximum TOC removal rate of 78.2% was obtained at pH 4. The decolorization and TOC removal of Orange II were monotonously increased with increasing ZVI dosage. To quantify the ZVI pre-treatment, the contributions of redox degradation, complexation/precipitation and adsorption to TOC removal by ZVI were defined. Novel kinetic models for the ZVI pre-treatment and activated-sludge post-treatment were developed. The proposed kinetic models satisfactorily predicted the transitional behaviors of the ZVI pre-treatment and activated-sludge post-treatment and the contributions of redox degradation, complexation/precipitation and adsorption to TOC removal by the ZVI pre-treatment. The complete removal of non-biodegradable azo-dye Orange II of 300 mgL−1 was accomplished by 78.2% removal after 360 min ZVI pre-treatment with the ZVI dosage of 1000 mgL−1 at pH 4 and subsequently 21.8% removal after 480 min activated-sludge post-treatment. The ZVI pre-treatment integrated with activated-sludge post-treatment was proved to be an effective strategy for treating non-biodegradable pollutants.

Application of graphene oxide nanosheets in the coagulation-flocculation process for removal of Total Organic Carbon (TOC) from surface water

Organic compounds in aquatic environments are one of the severe concerns in water treatment plants because of their role in increasing microbial growth in water supply systems and producing toxic by-products after chlorination. In other words, Natural Organic Matters (NOMs) can react with chlorine and be transformed into compounds, which were already proven to be carcinogenic. The primary purpose of this present study is assessing the role of Graphene Oxide (GO) in coagulation-flocculation process in TOC removal and the application of Fe3O4 for enhancing sedimentation rate. The physical, chemical, and morphological properties of GO and Fe3O4 were characterized by FT-IR, XRD, DLS, FE-SEM, and VSM. The experiments were designed using Box-Behnken to study the key parameters such as pH, GO, and FeCl3 concentration on TOC and turbidity removal. At the optimized points derived from Design-Expert software, GO concentration, FeCl3 concentration, and pH were reported 18 mg/L, 36 mg/L, and 7.5, respectively. The results were analyzed by UT isotherms, Radke-Prausnitz, Temkin, Langmuir, Freundlich, and Dubinin-Radushkevich, Redlich-Peterson. Radke-Prausnitz exhibited a lower error than the others. The maximum adsorption capacity of 1608 mg/g was obtained, which is related to the Langmuir isotherm. The experiment results demonstrated that using GO and Fe3O4 has significant effects on TOC and turbidity removal rate and settlement rate in coagulation-flocculation process.

Enhanced mineralization of bisphenol A by eco-friendly BiFeO3–MnO2 composite: Performance, mechanism and toxicity assessment

An eco-friendly BiFeO3–MnO2 composite with dual functionalities of adsorption and catalysis was successfully constructed by using a simple one-step hydrothermal method for the removal of bisphenol A (BPA) pollution from water. Several characterization methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), were applied to verify the combination of BiFeO3 and MnO2. BiFeO3–MnO2 (BFO–MO) exhibited excellent adsorption and catalytic activity compared with those of pure BiFeO3. The adsorption process followed a pseudo-second-order kinetic model and matched the Langmuir isotherm model. Effects of the catalyst and peroxymonosulfate (PMS) concentrations, pH and real water matrix were also analyzed, and BFO–MO displayed perfect adsorption and degradation performance under different conditions. Meanwhile, mineralization performance was tested, and the total organic carbon removal rate was nearly 85%. Moreover, BFO–MO exhibited good stability and reusability after five cycles. Based on radical quenching experiments, SO4− and OH were the primary reactive species responsible for BPA oxidation, and the possible reaction mechanism of BFO–MO/PMS was proposed. Finally, the degradation intermediates were identified, and the toxicity of intermediates was assessed. The novel BFO–MO composite is a promising catalyst for synchronous adsorption and degradation to purify wastewater.

Degradation of high-concentration p-nitrophenol by Fenton oxidation.

This work aimed to degrade high-concentration p-nitrophenol (PNP) by Fenton oxidation. We studied various reaction parameters during Fenton oxidation, such as the iron dosage (as Fe2+), the initial concentration and temperature of PNP, and the dosage of hydrogen peroxide (H2O2), especially the influence of temperature on the PNP degradation rate and degree. Under the addition of the same molar ratio of H2O2/Fe2+ and H2O2 dosage according to the theoretical stoichiometry, the PNP degradation rate and the removal rate of total organic carbon (TOC) increased significantly with the increase in the initial PNP concentration. Moreover, the oxidative degradation effect was significantly affected by temperature. The increased reaction temperature not only significantly reduced the Fe2+ dosage, but also greatly promoted the removal rate of chemical oxygen demand (COD) and TOC, and improved the utilization efficiency of H2O2. For example, when the initial concentration of PNP was 4,000 mg·L-1, and the dosage of Fe2+ was 109 mg·L-1 (H2O2/Fe2+ = 200), the removal rates of COD and TOC at 85 °C reached 95% and 71% respectively. Both were higher than the 93% COD removal rate and 44% TOC removal rate when the dosage of Fe2+ was 1,092 mg·L-1 (H2O2/Fe2+ = 20) at room temperature.

Iodine-doping-assisted tunable introduction of oxygen vacancies on bismuth tungstate photocatalysts for highly efficient molecular oxygen activation and pentachlorophenol mineralization

In this work, the tunable introduction of oxygen vacancies in bismuth tungstate was realized via a simple solvothermal method with the assistance of iodine doping. With the predictions afforded by theoretical calculations, the as-prepared bismuth tungstate was characterized using various techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, electron spin resonance spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The different concentrations of the oxygen vacancies on bismuth tungstate were found to be intensely correlated with iodine doping, which weakened the lattice oxygen bonds. Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as a result of iodine doping, the molecular oxygen activation was remarkably enhanced, thus endowing bismuth tungstate with high activity for the photocatalytic degradation of sodium pentachlorophenate. More encouraging is the total organic carbon removal rate of sodium pentachlorophenate over iodine-doped bismuth tungstate that exceeded 90% in only 2 h and was 10.6 times higher than that of the pristine bismuth tungstate under visible light irradiation. Moreover, the mechanism, through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tungstate is enhanced, was speculated based on the results of radical detection and capture experiments. This work provides a new perspective for the enhanced photocatalytic degradation of organochlorine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-doped bismuth tungstate.