First-order Degradation Rate Constants Research Articles

Complementary metalloporphyrin-based nanostructure decorated with silver nanoparticles for photocatalytic degradation of organic dyes

A hybrid composite photocatalyst, SA-T@Ag, was fabricated by the photoreduction of silver salts in the presence of nanomaterials composed of self-assembled complementary porphyrin triad SA-T. We confirmed the formation of SA-T@Ag from SA-T using various spectroscopic techniques, including X-ray diffraction (XRD), infrared (IR) spectroscopy, UV–visible spectroscopy, and fluorescence spectroscopy. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) investigations revealed that a substantial amount of silver nanoparticles (AgNPs) were deposited on the surface of SA-T and that the microstructure of SA-T was intact during photoreduction. The formation of AgNPs on the surface of SA-T reduced the band gap energy (Eg) of SA-T@Ag compared to that of SA-T. This not only improves its light-harvesting properties but also delays the recombination of photogenerated electron-hole pairs, which promotes more reactivity under visible light irradiation and improves the efficiency of polluted dye degradation. These photophysical properties are reflected in the degradation of methylene blue (MB) dye under visible light irradiation. The first-order degradation rate constant of MB dye within 45 min of visible light irradiation is much higher for SA-T@Ag (0.081 min−1) than SA-T (0.028 min−1). This report is of great importance in the field of environmental remediation and provides new opportunities for designing porphyrin-based photocatalytic systems as alternatives to conventional photocatalysts.

Removal of Diclofenac in Wastewater by Activated Sludge in Batch and Moving-bed Biofilm Reactor Experiments

This study aimed to determine the diclofenac removal in wastewater by sludge taken from an operating wastewater treatment facility. Laboratory experiments were conducted in two parts: batch and moving-bed biofilm reactor (MBBR) experiments. Results from batch experiments showed that 0.1–2 mg L-1 of diclofenac could be removed more than 80% within 72 h, and the removal efficiency reduced to less than 60% for higher concentrations. The increase in the removal rate from 0.00058 to 0.16527 mg L-1 h-1 was observed when the initial diclofenac concentration increased from 0.1 to 10 mg L-1, respectively. The average first-order rate constants of 24-h and 72-h degradation were calculated as 4.71 × 10-2 and 1.99 × 10-2 h-1, respectively. The removal of diclofenac by sludge was mainly from biodegradation by microorganisms in sludge, followed by the adsorption onto the sludge biomass. The addition of various metal ions in the studied range did not significantly increase the diclofenac removal; however, the addition of Ca2+, Co2+, Fe3+, Mn2+, and Zn2+ tended to increase both diclofenac removal rate and efficiency. This positive effect was reduced when the metal ion concentrations were increased up to 0.75 ppm. Lastly, results from an initial phase of continuous MBBR showed that sludge addition during the start-up also extended the diclofenac removal efficiency to one week compared with 3 days in the experiment without sludge addition. In conclusion, the findings show the capability of using activated sludge in diclofenac wastewater treatment by the traditional or alternative systems.

Insight into the humic acid/antibiotic complexation for boosting tetracycline degradation by heterogeneous persulfate activation

Little attention has been paid to the degradation of antibiotics in their bound states, although numerous ionizable organic micro-pollutants possessed a strong tendency towards complexing with natural organic matters (NOM) in aquatic ecosystems. This study systematically investigated the degradation kinetics of tetracycline (TCH) bound with humic acid (HA) versus free TCH in heterogeneous persulfate activation system. Contrary to the homogeneous UV/PS oxidation processes documented, the complexation with HA promoted the removal of TCH due to the adsorption behavior of TCH on the heterogeneous catalyst. The results displayed that higher first-order rate constants of HA-bound TCH degradation (up to 3.8 folds) were obtained compared to free TCH at varying TCH and HA concentrations. The presence of ionic strength, alkalinity and hardness had an inhibitory effect on the degradation of bound TCH, and the effect of pH was more significant due to the change of electrostatic complexation of TCH/HA. Differential absorbance spectra further identified that the degradation sensitivity followed the order of bound TCH ＞ free TCH in TCH/HA mixed systems. In addition, the enhanced interfacial electron transfer that played a dominant role in TCH oxidation may be responsible for the efficient removal of TCH in the bound state. Results of this study provide new insights into the NOM/antibiotics complexation for boosting the antibiotics degradation in heterogeneous catalysis.

Self-carbon-thermal-reduction strategy for boosting the Fenton-like activity of single Fe-N4 sites by carbon-defect engineering

Carbon-defect engineering in metal single-atom catalysts by simple and robust strategy, boosting their catalytic activity, and revealing the carbon defect-catalytic activity relationship are meaningful but challenging. Herein, we report a facile self-carbon-thermal-reduction strategy for carbon-defect engineering of single Fe-N4 sites in ZnO-Carbon nano-reactor, as efficient catalyst in Fenton-like reaction for degradation of phenol. The carbon vacancies are easily constructed adjacent to single Fe-N4 sites during synthesis, facilitating the formation of C-O bonding and lowering the energy barrier of rate-determining-step during degradation of phenol. Consequently, the catalyst Fe-NCv-900 with carbon vacancies exhibits a much improved activity than the Fe-NC-900 without abundant carbon vacancies, with 13.5 times improvement in the first-order rate constant of phenol degradation. The Fe-NCv-900 shows high activity (97% removal ratio of phenol in only 5 min), good recyclability and the wide-ranging pH universality (pH range 3-9). This work not only provides a rational strategy for improving the Fenton-like activity of metal single-atom catalysts, but also deepens the fundamental understanding on how periphery carbon environment affects the property and performance of metal-N4 sites.

Goat manure waste and palm oil mill effluent, viable crude oil degradation substrates: A thermodynamic and composting investigation studies

The composting and thermodynamic processes of crude oil (CO) degradation using the compost of goat manure origin (CGMO) and compost of palm oil mill effluent origin (CPOMEO) were studied. Microbial activity was investigated using the carbon dioxide (CO₂) evolution test. The physiochemical properties of the composts and that of the treated CO-contaminated soil (COCS) were also investigated. In particular, CGMO significantly improve CO degradation with the highest CO₂ evolution rate of 45 mg/g compared to the CPOMEO and the control. The CO degradation rates of 85.7 %, 71.4 %, and 14 % corresponded to the first-order CO degradation rate constants of 0.743 day−1, 0.689 day−1, and 0.136 day−1 for CGMO, CPOMEO, and control, respectively. The Fourier transforms infrared (FTIR) spectral pattern for both composts revealed adsorption bands that were identifiable with polysaccharides, potassium, and nitrogen, whereas the scanning electron microscope and energy dispersive spectrophotometry (SEMEDX) of CPOMEO indicated carbon and oxygen as the sole compositions. The negative ΔG and ΔH values indicated the spontaneity and exothermic nature of the CO composting process, respectively.

Phase-dependent reactivity of MnO2 catalysts for permanganate activation: Insight into the role of surface-adsorbed MnO4− species

The development of green and efficient heterogeneous catalysts for permanganate (Mn(VII)) activation remains unexplored. Given the different roles of crystal structures of MnO2 in many applications, it is of great significance to investigate the reactivity of MnO2 with different phases for Mn(VII) activation. In this study, it was found that the first-order rate constants for phenol degradation in the presence of 100 μM Mn(VII) follow an order of α-MnO2 (0.0884 min−1) > δ-MnO2 (0.0746 min−1) > β-MnO2 (0.0417 min−1) > γ-MnO2 (0.0396 min−1). The fact is in line with Mn(VII) adsorption, which can be related closely to the surface area, pore diameter, and isoelectric points of the catalysts. Other phenolic contaminants such as parachlorophenol and bisphenol A were also degraded efficiently by the Mn(VII)/α-MnO2 system. After coordination with surface Mn species in MnO2, the Mn–O bond of Mn(VII) is stretched with an increase in electron transfer reactivity and a decrease in oxygen atom transfer ability. A surface-promoted electron transfer process is then proposed for phenol degradation by the system. A good adaptability and reusability of the Mn(VII)/α-MnO2 system were observed. The influence of several parameters and comparisons with other catalysts were also studied. This work provides insights into the phase-dependent reactivity of MnO2 catalysts for Mn(VII) activation and pollutant degradation.

Degradation of bisphenol S – a contaminant of emerging concern - by synergistic ozone and percarbonate based AOP

Degradation of bisphenol S was studied using ozone activated by sodium percarbonate and the effectiveness of optimized process was compared with the peroxone process. The influence of several factors including sodium percarbonate concentration, ozone dose, pH, and water matrix were investigated. A synergetic coefficient of 3.84 was achieved for the combination of sodium percarbonate and ozone, confirming the effectiveness of this hybrid process. Scavenging tests revealed, that carbonate radicals, hydroxyl radicals, superoxide radicals, and singlet oxygen contributed to the degradation of bisphenol S. At the same operating condition, degradation effectiveness values of 99% and 81% were obtained by ozone combined with sodium percarbonate and hydrogen peroxide, respectively, demonstrating the superiority of sodium percarbonate over hydrogen peroxide in combination with ozone for the degradation of bisphenol S. Low concentration of inorganic anions had a negligible effect on the degradation, while carbonate ions increased the first-order degradation rate constant by 56%.

Role of Substituents in the Removal of Emerging Fluorinated Liquid Crystal Monomer Pollutants under the UV/Peroxydisulfate Treatment

Fluorinated liquid crystal monomers (LCMs) have been identified as emerging persistent and bioaccumulative chemicals with non-negligible environmental concentrations. Herein, 12 fluorinated LCMs including highly detected 4-ethoxy-2,3-difluoro-4′-(trans-4-propylcyclohexyl)biphenyl (EDPB) were selected as target fluorinated LCMs to investigate their structure–reactivity relationships by the ultraviolet/peroxydisulfate (UV/PDS) treatment. EDPB with biphenyl and ethoxy showed the highest first-order degradation rate constant of 1.93 h–1, while that of fluorinated LCMs with ethoxy (1.10–1.26 h–1) and biphenyl (0.45–0.56 h–1) and without biphenyl or ethoxy (0.27–0.30 h–1) decreased sequentially. HO• and SO4•– were identified as the main oxidative species in the UV/PDS treatment. Theoretical calculation suggested that biphenyl and ethoxy can significantly alter the electron distribution of LCM molecules, providing more attackable sites for HO• and SO4•– on LCMs with biphenyl or ethoxy. Oxalic acid, cyclohexane, and bicyclohexane were the main degradation products of fluorinated LCMs even though their degradation pathways were determined by their different molecular structures. Toxicity estimation revealed that fluorinated LCMs with high acute toxicity and developmental toxicity could be decomposed into some final products with less toxicity. This study is expected to fill knowledge gaps in the structure–activity relationships of fluorinated LCMs by the UV/PDS treatment.

Electrochemical Reduction of Halogenated Alkanes and Alkenes Using Activated Carbon-Based Cathodes.

Granular activated carbon (GAC) is used to sorb a broad range of halogenated contaminant classes, but spent GAC disposal is costly. Taking advantage of GAC's conductivity, this study evaluated the conversion of the GAC to cathodes for electrochemical reductive dehalogenation of 15 halogenated alkanes and alkenes exhibiting a diversity of structures (type of halogen, number of halogens, functional groups) and including contaminants of practical importance (e.g., trichloroethylene). Alkane degradation rates increased with the number of halogens and in the order: chlorine < bromine < iodine. Quantitative structure-activity relationships (QSARs) correlating experimental first-order degradation rate constants for alkanes with molecular descriptors associated with an outer-sphere one-electron transfer calculated using density functional theory indicated that correlations with molecular descriptors improved in the order: aqueous phase reduction potentials (E0,aq) < energy of the substrate's lowest unoccupied molecular orbital (ELUMO) < Marcus theory activation free energies (ΔG‡) ∼ gas-phase standard reduction free energies (ΔG0,gas). Chlorinated alkene degradation rates increased with decreasing number of chlorines, and QSAR correlations were opposite those of alkanes, indicating a different reaction mechanism. Degradation timescales ranged from 1 min to 3 h with halides as predominant products. These results suggest that the electrochemical reduction of halogenated alkanes and alkenes can be used to regenerate spent GAC.

Assessing a Large-Scale Sequential In Situ Chloroethene Bioremediation System Using Compound-Specific Isotope Analysis (CSIA) and Geochemical Modeling

Compound-specific isotopic analysis (CSIA) and geochemical modeling were applied to evaluate the effectiveness of an 800 m-long sequential in situ bioremediation (ISB) system in Northern Italy. The system was created for the clean-up of a polluted aquifer affected by chloroethenes. A hydraulically upgradient anaerobic (AN)-biobarrier-stimulated reductive dichlorination (RD) of higher chloroethenes (PCE, TCE) and a downgradient aerobic (AE)-biobarrier-stimulated oxidation (OX) of lower chloroethenes (DCE, VC) were proposed. Carbon CSIA and concentration data were collected for PCE, TCE, cis-DCE and VC and interpreted using a reactive transport model that was able to simulate isotopic fractionation. The analysis suggested that the combination of CSIA and modeling was critical to evaluate the efficiency of sequential ISBs for the remediation of chloroethenes. It was found that the sequential ISB could reduce the PCE, TCE and cis-DCE concentrations by &gt;99% and VC concentrations by &gt;84% along the flow path. First-order RD degradation rate constants (kRD) increased by 30 times (from kRD = 0.2–0.3 y−1 up to kRD = 6.5 y−1) downgradient of the AN barrier. For cis-DCE and VC, the AE barrier had a fundamental role to enhance OX. First-order OX degradation rate constants (kOX) ranged between kOX = 0.7–155 y−1 for cis-DCE and kOX = 1.7–12.6 y−1 for VC.

자외선/염소 및 자외선/과산화수소 기술에 의한 Microcystin-LR 처리 특성 비교

Microcystin-LR (MC-LR), the most widely known toxin produced in cyanobacteria, is problematic because of its toxicity. This study was carried out to evaluate the capability of ultraviolet photolysis of chlorine(UV/Cl₂) and ultraviolet photolysis of hydrogen peroxide(UV/H₂O₂). Results showed that direct photolysis with 254 nm UV irradiation achieved substantial toxin removal. In particular, in UV/Cl₂ oxidation treatment, the removal rate of MC-LR was improved through various radical reactions that were similar to UV/H₂O₂. In the UV/chlorine process at the pH of 7.0, UV irradiation amount of100 mJ/cm² and chlorine concentration of 0.3 mg/L, the MC-LR removal rate was 52.0%, indicating that the removal rate was increased by 24% compared to the UV only treatment. In the UV/chlorine and UV/H₂O₂ process at pH 7.0, the first-order degradation rate constants of MC-LR were 3.1×10^-3~3.6×10^-3 s^-1 and 2.9×10^-3~3.7×10^-3 s^-1, respectively. It was shown that the degradation rate constant of MC-LR was lowered by 19.4% at pH 9.0 compared to that of pH 7.0, where the analysis found that the change in pH affected oxidation ability. UV/H₂O₂ was not affected by pH. This result affects the energy consumption needed to meet the required 90% elimination of MC-LR.

Analysis of the Antioxidant Composition of Low Molecular Weight Metabolites from the Agarolytic Bacterium Alteromonas macleodii QZ9-9: Possibilities for High-Added Value Utilization of Macroalgae.

Agar accounts for ~60% of the dry weight of some red macroalgae, and the breakdown of this kind of polysaccharide releases high-value compounds; therefore, the resource utilization of agar is of great significance to improve the added value of these macroalgae. Herein, Alteromonas macleodii QZ9-9 isolated from tropical Gracilaria hainanensis in Hainan Island was characterized as an agarolytic bacterium, which displayed a high agar-degrading activity. The highest diameters of the degradation zones of the A. macleodii QZ9-9 and its extracellular-agarase (12.16 U/mL) were 41.46 mm and 22.89 mm, respectively, and the first-order degradation rate constants of those were 0.02 h−1 and 0.77 U−1, respectively. Importantly, the fermentation products of A. macleodii QZ9-9 exhibited antioxidant activity, and the peak of DPPH scavenging activity of 50 h fermentation products of this strain was up to 50.79% in the reaction for 1 h; the DPPH scavenging activity of low molecule metabolites (≤3 kDa) in particular was up to ~85.85%. A total of 766 metabolites were detected in the low molecule metabolites by metabolomics. The peptide-like metabolites, such as prolyl–histidine, isoleucyl–histidine, isoleucyl–proline and arginyl–proline, and the antioxidant maculosin were found in the top 20 metabolites with relatively high abundance. Additionally, the antioxidant activity of maculosin was further verified in this work. We concluded that the low molecule metabolites of A. macleodii QZ9-9 with relatively high antioxidant activity are interesting candidates for preparing desirable non-toxic antioxidants, thereby facilitating the high value-added utilization of macroalgae in the fields of cosmetic, food preservation, and pharmaceutical industries.

Preparation of surface-decorated mesoporous dendritic fibrous nanosilica/TiO2 for use in phenol degradation

Surface-decorated three-dimensional dendritic fibrous nanosilica (DFNS)/TiO2 are novel materials that may be used in degrading organic pollutants. The DFNS nanosphere substrate was synthesized using a one-pot hydrothermal technique and polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol/TiO2 (F127/TiO2) thin films were prepared via simple solvent volatilization-induced self-assembly method. The DFNS spheres and F127/TiO2 thin film were then combined and further annealed to obtain DFNS/TiO2 nanospheres. The as-synthesized DFNS mesoporous silica spheres exhibited unique fibrous morphologies, high specific surface areas, and uniform distributions. Standard characterization studies of the obtained mesoporous DFNS/TiO2 catalysts revealed that these catalysts were composed of amorphous SiO2 and anatase TiO2 with high specific surface areas of 525.3 m2∙g−1. The phenol degradation efficiencies of these catalysts were also studied. The amount of tetrabutyl titanate used as the Ti source was adjusted to obtain the optimal material with a first-order degradation rate constant of 0.0229 min−1. Thus, these surface modification DFNS/TiO2 materials display excellent catalytic properties, with potential applications in the fields of organic pollutant degradation and energy.

TACN-Mn catalyst use in an advanced oxidation process for efficient micropollutant abatement in wastewater: A transformation study of diclofenac and sulfamethoxazole

Advanced oxidation processes (AOP) are key technologies that can degrade micropollutants in wastewater treatment. In this study, we examined how well the TACN-Mn catalyst can be applied in environmentally relevant conditions (ambient temperature and near-neutral pH) in combination with hydrogen peroxide (H2O2). Furthermore, we investigated the degradation – including the reaction pathways, kinetics and transformation products (TPs) – of the two relevant micropollutants, diclofenac (DCF) and sulfamethoxazole (SMX), in two different water matrices. The rate constants we identified compared well to literature data and showed a strong pH dependency: The pseudo first-order rate constants for DCF degradation in ultrapure water varied from 4.45 × 10-3 min-1 to 1.06 × 10-1 min-1 when the pH was increased from 7.5 to 9.0, and for SMX degradation, the rate constants ranged from 1.62 × 10-3 min-1 to 2.33 × 10-2 min-1. In wastewater, the oxidation was still effective, but at a lower rate and to a lesser extent than that in ultrapure water. TPs and reaction pathways of DCF and SMX were elucidated by LC-HRMS. TPs formed were very similar to those reported in previous studies about reactions with OH radicals. These promising results are the prerequisites for further investigations to optimize and evaluate the TACN-Mn/H2O2-AOP.

Visible light assisted heterogeneous photo-Fenton-like degradation of Rhodamine B based on the Co-POM/N-TiO2 composites: Catalyst properties, photogenerated carrier transfer and degradation mechanism

The water pollution caused by industry emissions makes effluent treatment a serious matter to be settled. The heterogeneous photo-Fenton-like oxidation has been recognized as an effective means to degrade pollutants in water. In this paper, Co-polyoxometalate (POM) was decorated on N-TiO2 to form the hybrid Co-POM/N-TiO2 photo-Fentont-like catalys for the degradation of Rhodamine B (RhB) under visible light irradation. The pseudo first-order kinetic rate constant of RhB degradation in Co-POM/N-TiO2 catalyzed heterogeneous Fenton-like reaction was 9 times higher than those of N-TiO2 catalysts, and the degradation rate can reach to 97.47% within 40 min under visible light irradiation and neutral conditions (at pH=7). Experimental characterizations revealed that the doping efficiently of N into TiO2 not only expanded optical absorption of TiO2 into the visible region, but also was beneficial for the migration of electrons from bulk to surface of TiO2, and further facilitated the charge transfer from TiO2 to Co-POM clusters, resulting in the enhancement in photo-Fenton activity. Our work provides a new idea to construct the transition metal substituted POM/N-TiO2 hybrid catalysts with Fenton-like and visible light photocatalytic activities for the practical application of environmental remediation.

Microencapsulation of polyphenolic compounds recovered from red wine lees: Process optimization and nutraceutical study

Bioactive polyphenolic compounds, recovered by nanofiltration of Cabernet Sauvignon wine lees were encapsulated with maltodextrin to obtain a spray dried micro powder with enhanced nutritional value.A Central Composite Design allowed setting up optimal spray‒drying conditions using a commercial grape extract‒polyphenol as the reference polyphenolic source and considering maltodextrin concentration and the inlet temperature as independent variables. The optimized spray‒drying conditions were: maltodextrin 7 g/100 mL, inlet temperature 110 °C. These conditions were then applied to lees nanofiltrates and retentate. The obtained microcapsules were characterized according to the drying yield (62.9–82.0%), moisture (0.81–1.52%), total bioactive compounds (0.08‒0.57 mg GAE/100 mg dw), surface bioactive compounds (5.8–34.5%), microencapsulation efficiency (65.5–94.2%), polyphenols recovery (57.4–82.7%), and antioxidant activity (0.27‒0.36%). The microcapsules showed high stability and durability when subjected to accelerated aging using the stress‒heat test, as evaluated by calculating first-order rate constants of degradation of the encapsulated polyphenols and the reduction of radical scavenging capacity; stability over time was further confirmed by the reduced water activity of the micro powders (ranged 0.27–0.36). Lastly, an in‒vitro simulated digestion was performed under physiological conditions evidencing a different bioaccessibility of polyphenols among samples (ranged 50–78%) and suggesting potential for the encapsulated polyphenols to be absorbed at gastrointestinal level.

Magnetic Co-Co Prussian blue analogue catalyst for peroxymonosulfate activation to degrade organic dye

• Magnetic Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 can efficiently activate peroxymonosulfate. • Synergistic catalysis between Fe 3 O 4 and Co 3 [Co(CN) 6 ] 2 enhanced the degradation of RhB. • SO 4 − and OH played important roles in the degradation process of RhB. • Synergistic catalytic mechanism was proposed. • Magnetic properties of Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 facilitated the recovery of the catalyst. In this study, the Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 composite catalyst was synthesized by co-precipitation method. The morphology and the structure of Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 composites were characterized by XRD, FTIR, SEM, TEM, EDS, XPS, VSM. The results showed that the removal rate of RhB (10 mg/L) reached 99.5% in 40 min in the 0.4-Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 (200 mg/L) + PMS (50 mg/L) system with a pseudo first-order degradation rate constant (k) of 0.121 min −1 , which is nearly 2.16 times of that (0.0561 min −1 ) in the Co 3 [Co(CN) 6 ] 2 + PMS system and 18.9 times of that (0.0064 min −1 ) in the Fe 3 O 4 + PMS system. The observed synergistic catalysis between Fe 3 O 4 and Co 3 [Co(CN) 6 ] 2 in Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 enhanced the degradation of RhB. The electron paramagnetic resonance (EPR) analysis and quenching experiment indicated that SO 4 − and OH played important roles in the degradation process of RhB. A synergistic catalytic mechanism of PMS activation by Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 , which mainly involves the enhanced Co 2+ /Co 3+ cycle by Fe 2+ donated electrons, was proposed. In summary, owing to its easy preparation, excellent catalytic activity, and reusability, the Fe 3 O 4 /Co 3 [Co(CN) 6 ] 2 composite catalyst is a good candidate for remediation of contaminated water.

WITHDRAWN: Visible light assisted heterogeneous photo-Fenton-like degradation of Rhodamine B based on the Co-POM/N-TiO2 composites: Catalyst properties, photogenerated carrier transfer and degradation mechanism

The heterogeneous photo-Fenton-like oxidation has been recognized as an effective means to degrade pollutants in water. In this paper, Co-polyoxometalate (POM) was decorated on N-TiO 2 to form the hybrid Co-POM/N-TiO 2 photo-Fentont-like catalys for the degradation of Rhodamine B (RhB) under visible light irradation. The pseudo first-order kinetic rate constant of RhB degradation in Co-POM/N-TiO 2 catalyzed heterogeneous Fenton-like reaction was 9 times higher than those of N-TiO 2 catalysts, and the degradation rate can reach to 97.47% within 40 minutes under visible light irradiation and neutral condition (at pH=7). Experimental characterizations revealed that the doping efficiently of N into TiO 2 not only expanded optical absorption of TiO 2 into the visible region, but also was beneficial for the migration of electrons from bulk to surface of TiO 2 , and further facilitated the charge transfer from TiO 2 to Co-POM clusters, resulting in the enhancement in photo-Fenton activity. Our work provides a new idea to construct the transition metal substituted POM/N-TiO 2 hybrid catalysts with Fenton-like and visible light photocatalytic activities for the practical application of environmental remediation.

Efficient degradation of ibuprofen by electro-Fenton with microtubular gas- diffusion electrodes synthesized by wet-spinning method

• A novel microtubular gas diffusion electrode (MGDE) was fabricated and tested. • Characterized by physical methods in structural characteristics electrochemical performance. • The pH value has little effect on H 2 O 2 production, the current efficiency is 42.8%. • Efficient ibuprofen degradation in electro-Fenton system with MGDEs was optimized. Gas-diffusion electrodes (GDEs) are the efficient generator for the hydrogen peroxide, which plays an important role in the degradation of refractory organic contaminants by electro-Fenton processes. In this work, the microtubular gas-diffusion electrodes (MGDEs) were fabricated with the carbon nanotubes (CNTs) hollow fiber base by wet-spinning technology and then employed as gas-diffusion electrodes (GDEs). Characterized by FESEM, TEM, BET, XPS, the MGDEs were proved to be relatively compact and intact without fracture on the hollow fiber surface. Cyclic voltammetry test in three electrodes system was carried out to prove the catalysis effect of the surface functional groups in the electrochemical reactions. The time-course of H 2 O 2 production rate in the range of the different current density (10 ~ 25 mA cm −2 ), pH value (3.0 ~ 9.0) and electrolyte concentration (0.01 ~ 0.1 M Na 2 SO 4 ) were conducted to evaluated the electrochemical performance of MGDEs and explorer the optimal condition. The stability of electrocatalytic was also tested by repeated runs. Furthermore, several parallel-degradation process of the simulated wastewater with the 1.0 ~ 10.0 mg L -1 IBP were carried out in electro-Fenton system. Under the optimal conditions, the removal rate of IBP could reach 90.2% in 120 min with the pseudo first-order degradation rate constant of 0.01415 min −1 . It shows the potential of this system to degrade NSAIDs.

A novel UV based advanced oxidation process with electrochemical co-generation of chlorine and H2O2 for carbamazepine abatement: Better performance, lower energy consumption and less DBPs formation

To promote the performance of traditional UV/chlorine and UV/H2O2 processes, the novel UV based advanced oxidation process with electrochemical co-generation of chlorine and H2O2 (UV/E-Cl&H2O2) was for the first time used for degradation of carbamazepine (CBZ), a refractory antiepileptic drug with resistance to photodegradation and microbial degradation. Compared with UV/E-Cl and UV/E-H2O2 processes, the apparent first-order rate constant of CBZ degradation by UV/E-Cl&H2O2 process increased by 3.87 and 5.84 times respectively with a lower energy consumption (1.12 kWh/m3-log). Meanwhile, the disinfection by-products (DBPs) formation by the novel process was 21.4% less than that by UV/E-Cl process. Under the optimal condition of initial pH 7, applied current 600 mA and 15 mM NaCl, the UV/E-Cl&H2O2 process could almost completely eliminate CBZ within 4 min and obtain 57.8% TOC removal in 1 h. The mechanism of UV/E-Cl&H2O2 was investigated through processes comparison, quenching experiments, EPR analysis and determination of OH concentration. The generated radicals (i.e., OH and reactive chlorine species), especially OH, played a major role in CBZ removal. Besides, the possible degradation pathways of CBZ were proposed and the stability of UV/E-Cl&H2O2 process for CBZ removal was certified based on ten consecutive runs. The degradation of typical pollutants (sulfamethazine, rhodamine B, methylene blue, atrazine and phenol) and treatments in three kinds of real wastewater confirmed the wide application feasibility of the novel process. In summary, this study provides a novel efficient and energy-saving process for removing organic pollutants with promising perspectives..