Organic Carbon Removal Rate Research Articles

A double Z‐scheme catalyst BiOI/g‐C3N4/Bi2WO6 for enhanced photocatalytic activity

AbstractBACKGROUNDTo enhance photocatalyst activity, a Z‐scheme ternary heterojunction of g‐C3N4 and BiOI co‐modified with Bi2WO6 (BiOI/g‐C3N4/Bi2WO6 (BCB)) was prepared. The double Z‐scheme catalyst is advantageous but not well studied for compositing low‐cost g‐C3N4 with Bi‐containing components such as BiOI and Bi2WO6.RESULTSFor g‐C3N4 and BiOI, we determined the optimal doping ratios of 3 wt% BiOI/10 wt% g‐C3N4 /Bi2WO6. It catalyzed almost complete degradation of (100 mg L−1) rhodamine B (RhB) under visible light irradiation (95% in 20 min and 100% in 30 min), with a significant reaction kinetic constant of 0.245 min−1. The remaining high total organic carbon removal rate of RhB, even after five cycles of the experiment, and the good removal effect for different concentrations of tetracycline (TC) proved the effectiveness of the catalyst.CONCLUSIONThe e−, h+, and ·OH, ·O2− reactive species work together, leading to rapid pollutant degradation. The developed triple‐component double Z‐scheme heterojunction catalyst has promising applications in pollution control. © 2022 Society of Chemical Industry (SCI).

Application of QSAR for investigation on coagulation mechanisms of textile wastewater.

Coagulation is an effective preliminary treatment process for textile wastewater. In order to evaluate the effectiveness of the coagulation process, we performed quantitative structure activity relationship (QSAR) analyses with total organic carbon (TOC) removal rates (Rexp) as an index by three different coagulants (AlCl3, FeCl3, and MgCl2). The experimental results showed that the average Rexp of the three coagulants was 39.12%±2.60%, 51.60%±2.88%, and 49.95%±3.17%. Subsequently, 42 molecular descriptors of dye molecules were calculated by quantitative calculation softwares Gaussian 09, Material Studio 7.0, and Multiwfn 3.7, and then QSAR models were constructed by a multiple linear regression (MLR) method for the three coagulation systems. The developed QSAR models demonstrated excellent stability, robustness, and predictability with values of R2 =0.7677, 0.8015, and 0.7035, Q2INT =0.6067, 0.7026, and 0.5898, Q2EXT =0.5505, 0.5076, and 0.5697, respectively. Based on the analysis of quantum parameters, the coagulation mechanism for AlCl3, FeCl3 is primarily electrostatic adsorption as well as hydrogen bonding, while MgCl2 coagulates dyes mainly by electrostatic adsorption. This study provides an assessment of the removal rules and a feasible method for predicting dye removal rates in AlCl3, FeCl3, and MgCl2 coagulation process.

Synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater by electro-peroxone process.

Herein, a highly efficient electro-peroxone (E-peroxone) process with graphite felt as ozone diffusion electrode (ODE) was developed for the synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater. Under optimal conditions, the total organic carbon (TOC) removal rate of real hospital wastewater could reach 93.9%. Importantly, 126 pharmaceutical compounds (antibiotics, antivirals, analgesics, antiepileptics, hormones, and others) were determined in hospital wastewater by using ultra performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS). 110 pharmaceutical compounds could be efficiently degraded in E-peroxone system. Concurrently, the microbial community analysis through high-throughput sequencing showed that E-peroxone process exhibited an excellent disinfection effect in real hospital wastewater. Escherichia coli as a bacterial indicator could be completely inactivated in E-peroxone process·H2O2 and hydroxyl radical (OH) were found in E-peroxone system based on the results of chemical probe experiments and electron paramagnetic resonance (EPR) analysis. The in-situ generation of H2O2 from cathodic oxygen reduction in ODE can react with ozone to produce OH, and realize high efficiencies for the elimination of pharmaceutical and sterilization. This work established a green and effective way without extra addition of chemical reagents for high-efficiency treatment of real hospital wastewater.

Fabrication of Ce MOFs/Black-TNTs and CCM/Black-TNTs as high-efficiency photoelectrode for wastewater treatment and hydrogen production

The photoelectrocatalytic (PEC) process has attracted much attention in the field of the eliminating organic pollutants in the wastewater with simultaneous hydrogen evolution in the past decade. Development of photoelectrode with high photoelectrocatalytic activity and stability is a key to degrade of various toxic pollutants via PEC technology. Here, a novel nanoflower-like metal–organic framework loaded on black titanium dioxide nanotubes (Ce MOFs/Black-TNTs) were fabricated by the hydrothermal method. Moreover, in order to improve the efficiency of photocatalytic process, cobalt-copper-manganese complex-doped black titanium dioxide nanotubes (CCM/Black-TNTs) photocathode is prepared and coupled with the Ce MOFs/Black-TNTs photoanode for hydrogen evolution at the cathode in an H-type photoreactor. The total organic carbon (TOC) removal rate of 2, 4-dichlorophenoxyacetic acid (2, 4-D) reached 98% and the yield of H2 reached 160 mmol in 120 min of reaction. The possible PEC degradation pathway of 2, 4-D at Ce MOFs/Black-TNTs photoanode was also speculated by UV–visible absorption spectroscopy and liquid chromatography combined with mass spectrometer (LC-MS). This work could open new insight into rationally designing TiO2-based photoelectrocatalysts for PEC system.

Co nanoparticles encapsulated in nitrogen-doped nanocarbon derived from cobalt-modified covalent organic framework as peroxymonosulfate activator for sulfamerazine degradation

In this work, new covalent organic framework (COF) materials with high crystallinity and large specific surface areas were used as cobalt-loaded supports. Cobalt nanoparticle-embedded nitrogen-doped carbon porous catalysts (Co@COF) were obtained by high-temperature pyrolysis of the COF materials and cobalt salts. With multiple active sites (Co0, pyridine N, and graphitic N), Co@COF exhibited superior catalytic properties for peroxymonosulfate (PMS) activation toward the degradation of sulfamerazine (SMZ). The efficiency of SMZ degradation reached 92.4 % within 10 min and the total organic carbon (TOC) removal rate reached 70.3 % within 30 min. Using radical quenching experiments and electron paramagnetic resonance (EPR) analysis, sulfate radicals (SO4•−), hydroxyl radicals (•OH), and singlet oxygen (1O2) were identified in this system, while 1O2 was the dominant active species for SMZ removal. The degradation intermediates of SMZ in Co@COF/PMS were monitored by high performance liquid chromatography–time of flight mass spectrometry (HPLC–TOFMS).

Mn-Co/ɣ-Al2O3 coupled with peroxymonosulfate as efficient catalytic system for degradation of norfloxacin

As one of the most widely used antibiotics, fluoroquinolones (FQs) are frequently detected in water resources, posing a severe threat to human health and ecological environment. In the present study, Mn-Co/ɣ-Al2O3 material was synthesized as a highly effective activator for peroxymonosulfate (PMS) to degrade the typical FQs norfloxacin (NOR). The degradation efficiency of NOR was up to 90.7 % within 60 min using 2.0 mM PMS and 0.10 g/L Mn-Co/ɣ-Al2O3 at pH 6.6 and 25 °C. The NOR degradation obeyed pseudo-first-order reaction kinetics. High PMS concentration and temperature could enhance the NOR degradation. The presence of Cl− and humic acid could reduce the NOR degradation, whereas the NOR transformation was promoted with the addition of HCO3−. The degradation efficiencies (82.0–88.7 %) of other three FQs (ciprofloxacin, ofloxacin and enrofloxacin) showed the Mn-Co/ɣ-Al2O3 activated PMS process could be applied to remove the FQs. The degradation efficiencies of NOR (79.0–90.7 %) and the total organic carbon (TOC) removal rates (71.9–86.6 %) in the five continuous applications of Mn-Co/ɣ-Al2O3 indicated that Mn-Co/ɣ-Al2O3 has stable applicability in the PMS-based system. Radical scavenger experiments demonstrated that reactive species SO4−, OH and 1O2 were involved in the degradation process of NOR. The possible degradation pathways of NOR were speculated based on eleven identified products. Overall, the Mn-Co/ɣ-Al2O3 activated PMS process is an efficient method for rapid remediation of the FQs contaminated water.

Magnetic-activated carbon composites derived from sludge and steel converter slag for wastewater treatment

It is generally challenging to design efficient, low-cost, and environmentally friendly persulfate catalytic materials for wastewater purification. We report a simple strategy to synthesize a steel converter slag-sludge carbon catalyst with steel converter slag as a template, suspended sludge as a precursor, and one-step pyrolysis. A persulfate activator was used to remove phenol and organic matter from actual wastewater leachate. The catalyst had a shell structure, a large surface area, abundant adsorption groups, and polymetallic catalytic capacity. The catalytic capacity depended on zero-valent iron (Fe0), which effectively leached active Fe2+ composite to produce hydroxyl and persulfate radicals by activating persulfate. The maximum phenol degradation was 94.5% in 55 min with 2 mM persulfate, 100 mg/L catalyst, and 20 mg/L phenol, which was 6 and 44 times greater than that of pure sludge carbon and steel converter slag, respectively. For actual wastewater leachate, the maximum removal rate of total organic carbon was 77.75% with 0.15 M persulfate, 50 g/L catalyst, and 1125 mg/L total organic carbon; all the fluorescent substances were removed. This work provides a new approach for designing persulfate catalysts derived from green resources. Further, our approach is practical for the treatment of wastewater that has high concentrations of organic material.

Catalytic membrane electrode with Co3O4 nanoarrays for simultaneous recovery of water and generation of hydrogen from wastewater

Tremendous research efforts have been devoted to new methods of water decontamination and water splitting at low cost and less energy consumption. Herein, we developed a robust electrochemical strategy with an efficient membrane electrode to remove refractory organic pollutants and simultaneously produce pure hydrogen in wastewater. Firstly, the membrane anode was constructed with a three-dimensional (3D) nanoneedle array of Co3O4 and Ti membrane, exhibiting superior degradation of phenol and dye with Na2SO4 as the electrolyte in a conventional electrocatalytic membrane reactor (ECMR). For the phenol degradation, ≥99% removal efficiency of phenol, 99.5% chemical oxygen demand (COD) removal rate, 92.5% total organic carbon (TOC) removal rate, 88.7% current efficiency and 0.061 kW h (g COD)−1 energy consumption can be obtained. For the dye degradation, ≥99% decolor efficiency and 95.2% COD removal rate, 87.6% TOC removal rate, 82.1% current efficiency and 0.12 kW h (g COD)−1 energy consumption can be achieved. The obtained membrane electrode can provide more active CoOOH sites, dramatically increase the electric fields and overcome mass transfer limitation in a flow-through configuration, thereby significantly enhance the catalytic performance. Finally, we designed a H-type ECMR with the proton exchange membrane (PEM) as the separator for pure H2 production, i.e., PEM-ECMR, demonstrating superior degradation performance of phenol and dye, stable production of high-purity hydrogen (11–15 mL h−1), and excellent long-term stability (100 days) and low voltage input (below 3.0 V). This work demonstrates a promising pathway towards reducing cost and energy consumption for water decontamination and simultaneous hydrogen production.

Vancomycin removal using TiO2–clinoptilolite/UV in aqueous media and optimisation using response surface methodology

ABSTRACT Investigations have shown the traces of antibiotics in surface water, groundwater, wastewater treatment plants, and drinking water. However, conventional wastewater treatment is not entirely effective for vancomycin degradation. Advanced oxidation is one of the most widespread methods of antibiotic degradation in aqueous media. Vancomycin was quantified by high-performance liquid chromatography. The Response Surface Methodology (RSM) based on Central Composite Design (CCD) was used to explore and optimise the effect of the independent variables on vancomycin degradation. Independent variables were as follows: pH (3–11), vancomycin concentration (15–75 mg/L), TiO2–clinoptilolite (25–125 mg in 250 mL reactor volume), the temperature (25–45°C), and the reaction time (15–75 min). The validity and adequacy of the model were confirmed by the corresponding statistics (F–value = 111.5, correlation coefficient R2 = 0.98, adjusted R2 = 0.97, and prediction R2 = 0.95). The vancomycin degradation efficiency was 97% under optimal conditions (pH = 5, vancomycin concentration = 30 mg/L, TiO2-clinoptilolite content = 50.2 mg in a 250 mL reactor volume, temperature = 32.24°C, and reaction time = 50.9 min). This process followed the zero-order reaction kinetics model (R2 = 0.98), and the removal rate of Total Organic Carbon (TOC) under optimal conditions was 56%. The results indicated that supporting TiO2 on clinoptilolite particles could increase the photocatalytic properties.

Molecular insights into the catalytic oxidation of methanol-to-olefins wastewater with phosphoric acid modified sludge biochar

With the development of methanol-to-olefin (MTO) process, the effective disposal of wastewater was one key factor for the long-period and benign development of this technology. Herein, a sludge-based biochar catalyst (GSC-P) was synthesized and used in photo-Fenton reaction for the degradation of MTO wastewater from the outlet of a biological aerated filter. More iron was distributed on the surface of GSC-P catalyst, facilitating the photo-Fenton oxidation of MTO wastewater, with chemical oxygen demand (COD) removal rate of 75.4% and total organic carbon (TOC) removal rate of 62.5%. The 2223 unique molecular formulas assigned by a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in the original MTO wastewater showed that CHO compounds shared the lowest peak numbers (20.2%) but the highest peak abundance (51.6%) among the four groups. Besides, lipids, unsaturated hydrocarbons, lignins and proteins were the main structural types. After photo-Fenton treatment of 60 min, there were 56.7%–74.0% of compounds removed by the analysis of van Krevelen diagram, indicating that the MTO wastewater was degraded efficiently. Three possible evolution processes of dissolved organic matters during the photo-Fenton reaction were disclosed at the molecular-level.

Removal efficiency and mechanism of refractory organic matter from landfill leachate MBR effluent by the MoS2-enhanced Fe0/H2O2 system

In this study, molybdenum disulfide (MoS2) was used to enhance a zero-valent iron/hydrogen peroxide (Fe0/H2O2) Fenton-like system, which was able to remove refractory organic matter from the effluent produced during the treatment of landfill leachate by a membrane bioreactor (MBR). The MoS2/Fe0/H2O2 system could efficiently remove refractory organic matter (i.e., fulvic acid-like substances and humic-like substances) from the MBR effluent and also exhibited a strong synergistic effect. Under the conditions of initial pH = 3, H2O2 = 40 mmol/L, Fe0 = 0.4 g/L, MoS2 = 0.1 g/L, and t = 30 min, compared with a Fe0/H2O2 system, the absorbance UV254, chroma (CN), and total organic carbon (TOC) removal rates in MBR effluent treated with MoS2/Fe0/H2O2 increased to 48.68%, 63.85%, and 35.85%, respectively. Through the identification of reactive oxygen species (ROS), the hydroxyl radical (HO•) concentration and an analysis of the effective utilization rate of H2O2, as well as an analysis of the morphology of the material, the distribution of Fe compounds, valence changes, and the Fe ion concentration, it was proven that MoS2 promoted the cycling of Fe3+/Fe2+ in the Fe0/H2O2 process. The addition of MoS2 promoted the Fe3+/Fe2+ cycling reaction through the exposed Mo4+ active center, significantly promoting the decomposition of H2O2 and the formation of HO•. The MoS2/Fe0/H2O2 system was able to remove a wide range of aromatic organics, indicating the wide applicability of the system. This study developed a new method for the efficient removal of refractory organic matter from landfill leachate.

Preparation and immobilization of Bi2WO6/BiOI/g-C3N4 nanoparticles for the photocatalytic degradation of tetracycline and municipal waste transfer station leachate

Bi2WO6/BiOI nanoparticles were embedded into graphitic carbon nitride (g-C3N4) to fabricate a new visible-light-driven photocatalyst (Bi2WO6/BiOI/g-C3N4). Furthermore, the immobilization of Bi2WO6/BiOI/g-C3N4 was performed by a new method characterized by using polytetrafluoroethylene (PTFE) as an adhesive agent and boric acid (H3BO3) as a pore-forming agent. Bi2WO6/BiOI/g-C3N4 possesses the higher photocatalytic performance than Bi2WO6/BiOI and g-C3N4 for tetracycline degradation because of the enhancement of light absorption and electron/hole (e–/h+) pairs separation. After immobilization, Bi2WO6/BiOI/g-C3N4 still remained considerable activity and stability. For the degradation of tetracycline, the immobilized photocatalyst presented the degradation rate of over 90 % within 120 min, whereas the photocatalytic degradation of municipal waste transfer station (MWTS) leachate for 28 h presented the chemical oxygen demand (COD) removal rate of 56.1 % and the total organic carbon (TOC) removal rate of 50.4 %. Additionally, the biodegradability of the two test solutions was enhanced evidently after the photocatalytic degradation. This work mainly provides a new photocatalyst immobilization method to promote the large-scale application of photocatalytic degradation.

Preparation of Fe3O4@C with water treatment residuals and its potential in the magnetic coagulation process

The resource utilization of water treatment residuals is a hot topic in current research. In this work, a kind of carbon-doped magnetic nanoparticle (Fe 3 O 4 @C) was prepared using backwashing iron mud from the groundwater treatment plant as raw material. The Fe 3 O 4 @C was used for the magnetic coagulation (MC) process to evaluate the superiority of the MC process via comparing it with the traditional coagulation (TC) process. Meanwhile, the Fe 3 O 4 was also used for reference in the MC process to assess the potential and feasibility of the Fe 3 O 4 @C. The synthesized Fe 3 O 4 @C was characterized by SEM, TEM , XRD , VSM , and XPS . Then, coagulation performances and flocs properties were evaluated in both TC and MC processes. In addition, the various roles of magnetic particles in the MC process were discussed. The results showed that the participation of Fe 3 O 4 @C increased the turbidity removal rate from 90.3% to 96.8%, the ultra-violet absorbance at 254 nm (UV 254 ) removal rate from 81.4% to 86.5%, the dissolved organic carbon (DOC) removal rate from 60.4% to 66.9%, and the residual Al content dropped from 2.54 mg/L to 2.07 mg/L. Especially, it is found the Fe 3 O 4 @C had the potential to remove more small molecular weight organic matter during the coagulation process. The flocs were loose and easily broken due to the formation of the Al species-nanoparticle cluster. Fe 3 O 4 @C involved MC process can achieve the same water treatment efficiency as Fe 3 O 4 involved MC process, or even better. Especially, the magnetic seed of Fe 3 O 4 @C based on waste utilization can not only reduce the cost, but also has a good adsorption on small molecular organics. This provides a new reference way for the utilization of iron mud and the development of magnetic seed in the MC process. • Carbon-doped magnetic nanoparticles (Fe 3 O 4 @C) were prepared as magnetic seeds. • Fe 3 O 4 @C could improve the removal of small molecular organics by adsorption. • Recycle utilization of iron sludge was realized.

Synthesis of magnetic FeCo/BC composite by one-step pyrolysis for degradation of bisphenol A through peroxymonosulfate/peroxydisulfate activization

In this study, biomass carbon supported with iron and cobalt bimetal (FeCo/BC) was synthesized by a one-pot calcination method to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) for bisphenol A (BPA) degradation. Characterization with X-ray diffraction, X-ray photoelectron spectroscopy and high resolution transmission electron microscopy showed that Fe0, Fe3O4, Co0 and CoO nanocrystals were included in FeCo/BC materials. The degradation results showed Fe0.6Co0.4/BC had excellent catalytic activation performance for PMS or PDS. The Fe0.6Co0.4/BC (0.0050 g) combined with 0.25 g·L−1 of PMS could completely degrade 20 mg·L−1 BPA within 8 min, and the same amount of BPA could be removed with 0.020 g Fe0.6Co0.4/BC in the presence of 0.25 g·L−1 PDS within 20 min. The corresponding total organic carbon removal rates reached 83.49% and 77.5% respectively after 2 h. The Fe0.6Co0.4/BC also had good adaptability to solution pH and practical water body. After five cycles, the degradation rates of BPA in the two systems were all over 90%, and excellent magnetism was beneficial to the reuse of catalysts. Electron paramagnetic resonance and free radical quenching tests indicated that SO4•-, •OH, and 1O2 were the main active species involved in the BPA degradation. This work not only provided a promising catalyst for the degradation of organic pollutants, but also elucidated the synergistic effect between Fe-Co bimetal alloys during PMS and PDS activation, which would facilitate the design, synthesis, and application of catalytic materials with high efficiency.

Integrated MnO2 nanosheet ultrafiltration ceramic membrane with micro-nano bubbles for catalytic treatment of dye wastewater

Membrane filtration integrated with micro-nano bubbles (MNBs) is an attractive technology for treating dye wastewater given its efficiency and environmental compatibility. However, the amount of ·OH generated during the disintegration of MNBs is insufficient in practical applications. This work presents the characterisation of a modified Al2O3 ceramic membrane (CM) with the MnO2 nanosheet (MnO2/Al2O3 CM), which provides dual functions of membrane filtration and MNB catalysis. Here, a novel MNB catalytic membrane reactor (MNB-CMR) was constructed by applying the modified MnO2/Al2O3 CM for treating the simulated dye wastewater, i.e., methylene blue (MB). The MB degradation showed that the MNB-CMR improved 17% decolorization rate and 20% total organic carbon removal rate compared to the integrated MNB process with the non-modified CM. The MNB-CMR exhibited excellent catalytic performance and fouling resistance. Besides, the effects of MNB-CMR operational parameters such as the initial methylene blue (MB) concentration, reaction temperature, solution flux, and solution pH on the MB degradation performance were investigated. Based on the scavenging experiments of reactive oxygen species (ROS), the reaction of singlet oxygen (1O2) or hydroxyl radicals (·OH) was elucidated as the primary ROS responsible for the oxidation of MB in the MNB-CMR. In addition, the XPS results showed that the redox couple of Mn(IV)/Mn(III) on the surface of the MnO2/Al2O3 CM was responsible for MNB catalysis. Finally, we proposed a possible degradation pathway of MB. This work shows an attractive alternative wastewater treatment process to relieve membrane fouling and enhance MNB catalysis concurrently.

Iron (II) phthalocyanine loaded tourmaline efficiently activates PMS to degrade pharmaceutical contaminants under solar light

ABSTRACT Iron (II) phthalocyanine (FePc) is loaded on the surface of the tourmaline (TM) by the reflow method to obtain FePc/TM. This research effectively prevents the π-π stacking of FePc, increased the effective utilization rate of PMS activation under solar light, and further improved the catalytic performance of the catalytic system. The catalytic oxidation efficiency of FePc/TM on carbamazepine (CBZ) and sulfadiazine (SD) can reach 99% under solar light for 15 and 5 min, the total organic carbon (TOC) removal rate can reach 58% and 69% under solar light for 120 min. After 6 cycles, the CBZ removal rate remained above 95%. In addition, the FePc/TM catalytic system has an excellent removal rate for other pharmaceuticals. The results of spin-trapped electron paramagnetic resonance and classical quenching experiments show that FePc/TM can effectively activate PMS to generate active species under solar light, including superoxide radical (•O2 −), singlet oxygen (1O2), hydroxyl radicals(•OH), and sulphate radicals (SO4•−). The intermediates of CBZ were identified by Ultra-high performance liquid chromatography and high resolution mass spectrometry, and the degradation pathway was proposed. As the reaction progresses, all CBZ and intermediates are reduced and converted into small acids, or mineralized to H2O, CO2. This work provides an alternative method for the design of efficient activation of PMS activation catalysts under solar light to eliminate residual pharmaceuticals in actual water bodies.

Strengthen Air Oxidation of Refractory Humic Acid Using Reductively Etched Nickel-Cobalt Spinel Catalyst

Nickel-cobalt spinel catalyst (NCO) is a promising catalyst for air oxidation of humic acid, which is a typical natural refractory organic matter and a precursor of toxic disinfection by-products. In this study, reductive etchers, NaBH4 or Na2SO3, were used to adjust the NCO surface structure to increase the performance. The modified catalyst (NCO-R) was characterized, and the relationship between its intrinsic properties and catalytic paths was discovered. The results of O2-temperature programmed desorption, NH3-temperature programmed desorption, and X-ray photoelectron spectroscopy (XPS) demonstrated that reductant etching introduced oxygen vacancies to the surface of NCO and increased active surface oxygen species and surface acidity. In addition, the modification did not change the raw hollow sphere structure of NCO. The crystallinity and specific surface area of NCO-R increased, and average pore size of NCO-R decreased. XPS results showed that the ratio of Co3+/Co2+ in NCO-R decreased compared with NCO, while the ratio of Ni3+/Ni2+ increased. The results of H2-temperature programmed reduction showed that the H2 reduction ability of NCO-R was stronger. Due to these changes in chemical and physical properties, NCO-R exhibited much better catalytic performance than NCO. In the catalytic air oxidation of humic acid at 25 °C, the total organic carbon (TOC) removal rate increased significantly from 44.4% using NCO to 77.0% using NCO-R. TOC concentration of humic acid decreased by 90.0% after 12 h in the catalytic air oxidation using NCO-R at 90 °C.

Evaluation of the advanced oxidation process integrated with microfiltration for reverse osmosis to treat semiconductor wastewater

This study evaluated the filtration performance and energy consumption of three different reverse osmosis (RO) membranes (ESPA2-LD, RE4040-BE, and TMG10D) for treating semiconductor wastewater. A ceramic membrane combined with ozone for RO pre-treatment and the influence of ozone injection on the filtration and energy consumption efficiency of RO were investigated. A flat-sheet ceramic membrane comprising Al2O3/SiO2-ZrO2 was used to treat real and synthetic semiconductor wastewater as feed water. The deionized water (DI) permeabilities of RO membranes were 144.6, 94.22, and 156.6 LMH/bar, respectively. The microfiltration process that used ozone reduced the permeability of all RO processes, and the total organic carbon (TOC) removal rate decreased when ozone was applied. The application of ozone on power consumption was inconclusive, and its effect was unclear indicating an increase 3.37%, 4.48%, and 11.6% when filtrated with ozone, respectively. TMG10D showed the highest permeability followed by ESPA2-LD and RE4040-BE, for both, the real and synthetic wastewaters. However, ESPA2-LD showed the highest salt and TOC rejection followed by RE4040-BE and TMG10D. TMG10D exhibited the lowest energy consumption per ton of filtered water followed by ESPA2-LD and RE4040-BE. ESPA2-LD was determined to be the most suitable membrane in terms of the water quality stability and energy consumption in RO to treat semiconductor wastewater.

Fe@Fe2O3-loaded biochar as an efficient heterogeneous Fenton catalyst for organic pollutants removal.

With increased demand for various chemical raw materials, sudden pollution incidents are more prone to occur during their transportation and usage, threatening the environment and human health. In this study, discarded tea stalks were recycled into composite materials (FSC-X00: X represents the calcination temperature) by impregnating tea stalks in Fe2+ solution combined with subsequent calcination. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) patterns verified the existence of Fe0 and Fe2O3, and Fe2O3 was gradually reduced to Fe0 when the calcination temperature was raised from 700 °C to 900 °C. FSC-X00 was adopted as a heterogeneous catalyst for activating H2O2 to quickly degrade phenol in the water system. The degradation experiments indicated that FSC-600 exhibited superior degradation performance for phenol (20 mg/L) within 5 min and 80% total organic carbon (TOC) removal rate at pH = 3 within 30 min. The effects of the calcination temperature, the pH value and the amount of H2O2 on the degradation efficiency were investigated. Competing experiments showed that fulvic acid (FA) and inorganic salts Na+ had little effect on the degradation performance. The FSC-600 catalyst can be reused by thermal reduction. In addition, it was found that FSC-600 has a good degradation effect on ciprofloxacin (CIP), norfloxacin (NOR) and enrofloxacin (ENR), indicating that FSC-600 catalysts are a promising candidate for quick degradation of organic pollutants by Fenton reaction. Electron paramagnetic resonance (EPR) spectra analysis indicated that •OH is the dominant reactive oxygen species (ROS) and part 1O2 from O2 also participated in the degradation. This study provides an example of creating catalysts from organic solid waste for use in emergency treatment for phenol.

Antifouling BaTiO3/PVDF piezoelectric membrane for ultrafiltration of oily bilge water.

Barium titanate/polyvinylidene fluoride (BaTiO3/PVDF) piezoelectric membrane was successfully prepared and generated in-situ vibrations to reduce membrane fouling by applying alternating current (AC) signal for oily bilge water ultrafiltration. The effect of in-situ vibration on membrane fouling was investigated through changing in the excitation alternating voltage and its frequency, pH, crossflow rate. The results indicated that the piezoelectric membrane by applying AC signal remarkably alleviated the membrane fouling for bilge water ultrafiltration. The membrane fouling decreased with increasing the AC signal voltage. The final steady-state permeate flux from the piezoelectric membrane for bilge water ultrafiltration increased with the AC signal voltage, raising it by up to 63.4% at AC signal voltage of 20 V compared to that of the membrane without applying AC voltage. The high permeate flux was obtained at the resonant frequency of 220 kHz. During the 50-h ultrafiltration of bilge water with the piezoelectric membrane excited at 220 kHz and 15 V, the permeate flux from the membrane was stable. The oil concentration in outflow from the piezoelectric membrane was below 14 ppm, which met the discharged level required by IMO convention. The total organic carbon removal rate in bilge water was over 94%.