Hydroxyl Radical Trapping Research Articles

A hollow core-shell TiO2/NiCo2S4 Z-Scheme heterojunction photocatalyst for efficient hydrogen evolution

Constructing heterojunctions have received significant attention in photocatalysis because of their efficient separation of photogenerated carriers and improving light utilization efficiency. Bimetallic sulfides (e.g. NiCo2S4) are applied in electrocatalysis and supercapacitors that can be coupled with TiO2 to form a heterojunction. Owing to the staggered energy band arrangement between TiO2 and NiCo2S4, the establishing of a Z-scheme heterojunction between them is expected to enhance the carrier separation efficiency and reduce the sulfide photo-corrosion. However, the application of NiCo2S4 in photocatalysis and studies on the mechanism of the TiO2/NiCo2S4 Z-scheme heterojunction have seldom been reported. In this work, we obtained a hollow core-shell TiO2/NiCo2S4 Z-scheme photocatalyst through a solvothermal method for photocatalytic hydrogen evolution (PHE). The PHE rate of the optimized TiO2/NiCo2S4-0.3 is 8.55 mmol g−1 h−1, approximately 34 times higher than pure TiO2, 94 times higher than pure NiCo2S4. The remarkable photocatalytic activity can be ascribed to the hollow structure and the in-situ constructed Z-scheme heterojunction. The photogenerated charge transfer mechanism is revealed by hydroxyl radical trapping experiments and electron paramagnetic resonance (EPR) characterization. The in-situ construction of the Z-scheme heterojunction not only enhances the efficiency of separating the photogenerated carriers but also reduces the photo-corrosion of NiCo2S4. This study proposes an effective strategy for the design of TiO2-based Z-scheme heterojunctions and the application of NiCo2S4 in photocatalysis.

Carbon nanoparticles derived from rubber seed shells by hydrothermal synthesis for fluorescent cerium(III) sensing and application in hydroxyl radical trapping

Carbon nanoparticles (CNPs) from rubber seed shells were synthesized by hydrothermal carbonization. The functional group and morphology of CNPs were characterized by Fourier Transform-Infrared Spectroscopy (FT-IR) and Transmission Electron Microscopy (TEM), respectively. Water-soluble CNPs exhibited an excellent blue fluorescence which can be applied for cerium (Ce3+) detection. In addition to taking advantage of high fluorescent Ce3+-CNPs, the corresponding reaction for detecting active hydroxyl radical was studied through the scavenging activity by turning off of emission.

Managing Encapsulated Oil Extract of Date Seed Waste for High Hydroxyl Radical Scavenging Assayed via Hybrid Photo-Mediated/Spectrofluorimetric Probing

This work addresses two research topics: the first concerns the specific/sensitive trapping of hydroxyl radicals (•OH), and the second concerns the efficacy of encapsulating natural antioxidants, potentially lengthening their preservation activity. For context, nano-titania was solar-irradiated to produce •OH, which was spectrofluorimetrically assessed, based on the selective aromatic hydroxylation of the non-fluorescent sodium terephthalate to 2-hydroxyterephthalate fluorophore. Fluorescence intensity is proportional to generated •OH. Thus, a simple/rapid indirect method was utilized to assess •OH precisely. Accordingly, novel photoluminescent system is outlined in order to assess the scavenging potentiality of •OH in date seed oil (DSO) in both its pure and encapsulated formulations (ECP–DSO), i.e., when fresh and 5 months after extraction and encapsulation, respectively. With the addition of 80 μg/mL DSO or ECP–DSO, the efficacy of •OH scavenging amounted to 25.12 and 63.39%, which increased to 68.65 and 92.72% when 200 μg/mL DSO or ECP–DSO, respectively, was added. Moreover, the IC50 of DSO and ECP–DSO is 136.6 and 62.1 µg/mL, respectively. Furthermore, DSO and ECP–DSO decreased the kinetics for producing •OH by ≈20 and 40%, respectively, relative to •OH generated in the absence of antioxidant. This demonstrates the benefits of encapsulation on the preservation activity of natural antioxidants, even after five months after extraction, in terms of its interesting activity when compared to synthetic antioxidants. The developed fluorimetric •OH probing upgrades antioxidant medicines, thus paving the way for theoretical/practical insights on mechanistic hydroxyl radical-damaging biology.

An in-situ assembled titanate nanotube-based dimensionality-hybrid for enhanced photocatalytic hydrogen generation

Dimensionality-hybrids are potentially functional materials due to their great advantages in obtaining high light absorption and effective electron transfer, which are vital in energy conversion and electronic devices. Herein, a novel dimensionality-hybrid was facilely fabricated by in-situ assembling two-dimensional Co (II) meso-tetra (4-carboxyphenyl) porphyrin metal organic framework (Co-TCPP MOF) on one-dimensional titanate nanotubes (TNTs). The enhanced light absorption, abundant active sites and improved charge separation and transfer were achieved in the special “dimensionality-hybrid”. Importantly, the obtained TNTs/Co-TCPP MOF exhibited large photocatalytic H2 production compared with some comparisons without adding any cocatalysts. Furthermore, the mechanism of charge transition in the nanohybrid was explored by hydroxyl radical trapping experiment. This research will pave a new way in the fabrication and mechanism exploration of the nano photocatalysts for efficient H2 evolution.

Functionalized nanozyme with drug loading for enhanced tumour combination treatment of catalytic therapy and chemotherapy.

Nanozyme-based tumour catalytic therapy has attracted widespread attention in recent years, but the therapeutic efficacy is limited due to the trapping of hydroxyl radicals (˙OH) by endogenous glutathione (GSH) in the tumour microenvironment (TME). Zr/Ce-MOFs/DOX/MnO2 is constructed in this work to serve as a new kind of nanozyme for combination chemotherapy and catalytic treatment. Zr/Ce-MOFs can produce ˙OH in a mimic TME, and the MnO2 on the surface could deplete the GSH, further promoting the ˙OH generation. The pH/GSH dual stimulation accelerates the release of anticancer drug doxorubicin (DOX) in tumour tissue for enhanced tumour chemotherapy. Moreover, Mn2+ produced by the reaction of Zr/Ce-MOFs/DOX/MnO2 and GSH can be used as the contrast agent for T1-MRI. The potential antitumour effect of Zr/Ce-MOFs/DOX/MnO2 is demonstrated by in vitro and in vivo cancer treatment tests. This work thus provides a new nanozyme-based platform for enhanced combination chemotherapy and catalytic treatment for tumours.

Solar light mediated anthracene abatement in aerated aqueous media using a thermoplastic nanocomposite photocatalyst.

Polycyclic aromatic hydrocarbons (PAHs) are the most widespread xenobiotic pollutants in water and their abatement usually involves expensive and energy-consuming treatments. In this work, anthracene (AN) was selected as the recalcitrant model of PAHs and its solar light-stimulated heterogeneous photocatalytic abatement in aerated aqueous media was investigated using a new TiO2 derived thermoplastic nanocomposite in thin film form. The results were also compared with the benchmark TiO2 photocatalyst in slurry form. Finally, the possible contribution of reactive intermediates such as hydroxyl radical, AN radical cation and singlet oxygen, was investigated by using a hydroxyl radical trap and laser flash photolysis. Based on the obtained results, a feasible mechanism for AN photodegradation, which involves hydroxyl radical as the key oxidizing species is proposed.

Redox Potential Correlates with Changes in Metabolite Concentrations Attributable to Pathways Active in Oxidative Stress Response in Swine Traumatic Shock.

Oxidation-reduction (redox) reactions, and the redox potential (RP) that must be maintained for proper cell function, lie at the heart of physiologic processes in critical illness. Imbalance in RP reflects systemic oxidative stress, and whole blood RP measures have been shown to correlate with oxygen debt level over time in swine traumatic shock. We hypothesize that RP measures reflect changing concentrations of metabolites involved in oxidative stress. To test this hypothesis, we compared blood and urine RP with concentrations of multiple metabolites in a swine traumatic shock model to identify meaningful RP-metabolite relationships. Seven swine were subjected to traumatic shock. Mixed venous (MV) RP, urine RP, and concurrent MV and urine metabolite concentrations were assessed at baseline, max O 2 Debt (80 mL/kg), end resuscitation, and 2 h post-resuscitation. RP was measured at collection via open circuit potential using nanoporous gold electrodes with Ag/AgCl reference and a ParstatMC potentiostat. Metabolite concentrations were measured by quantitative 1 H-NMR spectroscopy. MV and urine RP were compared with time-matched metabolites across all swine. LASSO regression with leave-one-out cross validation was used to determine meaningful RP/metabolite relationships. Metabolites had to maintain magnitude and direction of coefficients across 6 or more swine to be considered as having a meaningful relationship. KEGG IDs of these metabolites were uploaded into Metscape for pathway identification and evaluation for physiologic function. Meaningful metabolite relationships (and mean coefficients across cross-validation folds) with MV RP included: choline (-6.27), ATP (-4.39), glycine (5.93), ADP (1.84), glucose (15.96), formate (-13.09), pyruvate (6.18), and taurine (-7.18). Relationships with urine RP were: betaine (4.81), urea (4.14), glycine (-2.97), taurine (10.32), 3-hydroxyisobutyrate (-7.67), N-phenylacetylglycine, PAG (-14.52), hippurate (12.89), and formate (-5.89). These meaningful metabolites were found to scavenge extracellular peroxide (pyruvate), inhibit ROS and activate cellular antioxidant defense (taurine), act as indicators of antioxidant mobilization against oxidative stress (glycine + PAG), and reflect renal hydroxyl radical trapping (hippurate), among other activities. Real-time RP measures demonstrate significant relationships with metabolites attributable to metabolic pathways involved in systemic responses to oxidative stress, as well as those involved in these processes. These data support RP measures as a feasible, biologically relevant marker of oxidative stress. As a direct measure of redox state, RP may be a useful biomarker and clinical tool in guiding diagnosis and therapy in states of increased oxidative stress and may offer value as a marker for organ injury in these states as well.

Spin Trapping Hydroxyl and Aryl Radicals of One-Electron Reduced Anticancer Benzotriazine 1,4-Dioxides.

Hypoxia in tumors results in resistance to both chemotherapy and radiotherapy treatments but affords an environment in which hypoxia-activated prodrugs (HAP) are activated upon bioreduction to release targeted cytotoxins. The benzotriazine 1,4-di-N-oxide (BTO) HAP, tirapazamine (TPZ, 1), has undergone extensive clinical evaluation in combination with radiotherapy to assist in the killing of hypoxic tumor cells. Although compound 1 did not gain approval for clinical use, it has spurred on the development of other BTOs, such as the 3-alkyl analogue, SN30000, 2. There is general agreement that the cytotoxin(s) from BTOs arise from the one-electron reduced form of the compounds. Identifying the cytotoxic radicals, and whether they play a role in the selective killing of hypoxic tumor cells, is important for continued development of the BTO class of anticancer prodrugs. In this study, nitrone spin-traps, combined with electron spin resonance, give evidence for the formation of aryl radicals from compounds 1, 2 and 3-phenyl analogues, compounds 3 and 4, which form carbon C-centered radicals. In addition, high concentrations of DEPMPO (5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide) spin-trap the •OH radical. The combination of spin-traps with high concentrations of DMSO and methanol also give evidence for the involvement of strongly oxidizing radicals. The failure to spin-trap methyl radicals with PBN (N-tert-butylphenylnitrone) on the bioreduction of compound 2, in the presence of DMSO, implies that free •OH radicals are not released from the protonated radical anions of compound 2. The spin-trapping of •OH radicals by high concentrations of DEPMPO, and the radical species arising from DMSO and methanol give both direct and indirect evidence for the scavenging of •OH radicals that are involved in an intramolecular process. Hypoxia-selective cytotoxicity is not related to the formation of aryl radicals from the BTO compounds as they are associated with high aerobic cytotoxicity.

Novel photoelectrochemically combined mechanical polishing technology for scratch-free 4H-SiC surface by using CeO2-TiO2 composite photocatalysts and PS/CeO2 core/shell abrasives

4H-SiC is a promising next-generation semiconductor. To obtain a scratch-free SiC surface with less/no residual oxide layer at an ideal material removal rate (MRR), a novel photoelectrochemically combined mechanical polishing (PECMP) technique was proposed. Polystyrene (PS)/CeO2 core/shell abrasives and CeO2-TiO2 composite photocatalysts immobilized on a titanium mesh were synthesized and characterized. The results of hydroxyl radical trapping tests present that the strongest photocatalytic activity is achieved by CeO2-TiO2 when UV-light and anodic bias are applied simultaneously (the optimal conditions). SiC-PECMP comparison tests were conducted in water containing 6.5 wt% PS/CeO2 on a home-made polisher, and after polishing, surface morphologies, surface roughness values (Ra) and MRRs were compared. The best polishing results (Ra: 0.738 nm, MRR: 1.109 μm/h) are realized under the optimal conditions. This was further demonstrated by another verification test, and a scratch-free surface (Ra: 0.113 nm) with less residual oxide layer was obtained. The scratch-free surface is attributed to the elastic core/shell abrasives and to the mild photocatalytic reaction. The ideal MRR is ascribed to the enhanced photocatalytic activity of the composite photocatalysts. Therefore, the feasibility of the proposed method is demonstrated, and this technique may be utilized to manufacture other semiconductors.

CHARACTERISTICS AND THERAPEUTIC EFFECTS OF THE NOVEL FREE RADICAL SCAVENGER – EDARAVONE

Edaravone is the first free radical scavenger which approved clinically and has an ability to decrease the level of free radicals in cells. Edaravone is a strong antioxidant, which can protect different cells (e.g. endothelial cells) against damage by ROS by inhibiting the lipoxygenase metabolism of arachidonic acid, by trapping hydroxyl radicals, by increasing prostacyclin production, by inhibiting alloxan-induced lipid peroxidation, etc. Because of that, Edaravone is used in treatment of diseases which are associated with oxidative stress. Key words: edaravone, free radical, antioxidant, neuroprotective agent, oxidative stress

Polypyridyl-Based Copper Phenanthrene Complexes: Combining Stability with Enhanced DNA Recognition.

We report a series of copper(II) artificial metallo-nucleases (AMNs) and demonstrate their DNA damaging properties and in-vitro cytotoxicity against human-derived pancreatic cancer cells. The compounds combine a tris-chelating polypyridyl ligand, di-(2-pycolyl)amine (DPA), and a DNA intercalating phenanthrene unit. Their general formula is Cu-DPA-N,N' (where N,N'=1,10-phenanthroline (Phen), dipyridoquinoxaline (DPQ) or dipyridophenazine (DPPZ)). Characterisation was achieved by X-ray crystallography and continuous-wave EPR (cw-EPR), hyperfine sublevel correlation (HYSCORE) and Davies electron-nuclear double resonance (ENDOR) spectroscopies. The presence of the DPA ligand enhances solution stability and facilitates enhanced DNA recognition with apparent binding constants (Kapp ) rising from 105 to 107 m-1 with increasing extent of planar phenanthrene. Cu-DPA-DPPZ, the complex with greatest DNA binding and intercalation effects, recognises the minor groove of guanine-cytosine (G-C) rich sequences. Oxidative DNA damage also occurs in the minor groove and can be inhibited by superoxide and hydroxyl radical trapping agents. The complexes, particularly Cu-DPA-DPPZ, display promising anticancer activity against human pancreatic tumour cells with in-vitro results surpassing the clinical platinum(II) drug oxaliplatin.

Synthesis, spectroscopic characterization, and in vitro antioxidant activity of polyglycidylmethacrylate/polyindole conducting polymer composites.

Polyglycidylmethacrylate/polyindole (PGMA/PIN) conducting polymer composites having five different compositions were prepared chemically using FeCl3 as an oxidant agent in chloroform solution and nitrogen atmosphere at 10°C. The conducting polymer composites were characterized by FTIR spectroscopic technique, scanning electron microscopy (SEM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA) measurements. It is seen that morphological structure of composite is different from PIN and PGMA. PGMA/PIN conducting polymer composite including 50% of PIN has a nonuniform and less homogenous structure compared to the PIN and PGMA polymer. in vitro antioxidant activity such as reduction force, superoxide radical removal activity, hydroxyl radical trapping activity, MDA measurements in Saccharomyces cerevisiae cells of PGMA/PIN conducting polymer composite was investigated. It was observed that the reduction force capacities decreased as PIN content and increased due to the percentage of composite of PGMA content. in vitro studies of synthesized composites have shown us that these compounds possess new antioxidant properties.

Degradation of nitrobenzene in wastewater by O3/FeOOH in a rotating packed bed

In this study, O3/FeOOH was used for degradation of nitrobenzene (NB) wastewater in a rotating packed bed (RPB) in order to improve the efficiency of heterogeneous catalytic ozonation, and the effects of high gravity factor β, FeOOH concentration, inlet O3 concentration, liquid flow rate, initial pH and initial NB concentration on the degradation rate of NB and the removal rate of COD were also investigated. The results show that under the optimal conditions (high gravity factor β = 40, FeOOH concentration = 0.5 mg L−1, inlet O3 concentration = 40 mg L−1, liquid flow rate = 60 L h−1, initial pH = 7, initial NB concentration = 100 mg L−1), the degradation rate of NB reaches 100 % after 20 min and the removal rate of COD reaches 94 % after 40 min. Tertiary butyl alcohol (TBA)is added to trap hydroxyl radicals, and the results show that the oxidation by hydroxyl radicals plays a dominant role in the degradation of NB. Gas chromatography-mass spectrometry was performed to investigate the degradation intermediates and the possible degradation pathways of NB by O3/FeOOH in the RPB were also proposed.

Understanding Amyloid-Beta Plaque Formation By Monitoring the Redox Activity of Copper at the Active Site

The Amyloid β peptide (Aβ-42) can be expressed through cleavage of a precursor protein (APP) during post-translational modification as a result of oxidative stress in the brain. Once expressed, the peptide will readily form binding interactions with free metal ions, particularly Cu2+, initiating a series of redox reactions that result in the production of Reactive Oxygen Species (ROS) and amyloid plaques within the brain. This process has been implicated as the major contributing factor in neurodegeneration in Alzheimer’s patients. An increasingly promising area of study in the treatment of AD is to disrupt this pathway using metal ion chelation, which can serve as a form of therapeutic treatment. The work presented herein focuses on different copper coordination compounds and their redox activity using various ligands such as glycine, beta alanine, phenylalanine, 2,2’-bipyridine (bipy), 2,2’-thiodipyridine (DPS), 2,2’-dipyridylamine (DPA), and 1,10-phenanthroline-2-thiopyridine (TPP). Utilizing Cyclic Voltammetry to monitor redox activity, the more stable ligand complexes resulted in a more quasi-reversible cyclic voltammogram, allowing for potential redox cycling between Cu2+ and Cu+ at the Aβ-42 active site. The CV results correlated well with hydroxyl radical trapping experiments that measured the rate of hydroxyl radical production in each complex, and a relationship between redox activity and hydroxyl radical production was observed. With the Aβ-42 peptide, these coordination complexes were analyzed using Atomic Force Microscopy (AFM) to correlate the rate of fibril formation to plaque formation. These results provide valuable insight into ligand design characteristics important for the development of potential therapeutic treatments that slow AD progression.

Fundamental study of the ultrasonic induced degradation of the popular antihistamine, diphenhydramine (DPH)

Diphenhydramine (DPH) the active ingredient in Benadryl, has been detected in streams, rivers and other surface water sources. As a bioactive compound, DPH impacts human health even at low concentrations. Ultrasonic irradiation at 640 kHz leads to the rapid degradation of DPH in aqueous solution. Radical scavenging experiments and detailed product studies indicate the DPH degradation involves direct pyrolysis and degradation reactions mediated by the hydroxyl radicals produced during cavitation. The degradation can be modeled by pseudo-first order kinetics yielding rate constants k of 0.210, 0.130, 0.082, 0.050, 0.035, 0.023 min−1 at the initial concentrations of 2.8, 5.2, 13.9, 27.0, 61.0, 160.0 μmol L−1, respectively. The degradation process follows the Langmuir-Hinshelwood (heterogeneous) model with a partition coefficient, KL-H = 0.06 μmol·L−1and reactivity constant kr = 1.96 μmol min−1·L−1. A competition kinetic study conducted employing the hydroxyl radical trap, coumarin, illustrates that DPH was degraded primarily by hydroxyl radical mediated processes. Computational studies employing Gaussian 09 basis set provide fundamental insight into the partitioning of the reaction pathways and the degradation mechanisms. The study demonstrates the ultrasonic degradation of DPH is rapid, follows simple kinetic expressions and is accurately modeled using computational methods.

Optimization and detailed stability study on Pb doped ceria nanocubes for enhanced photodegradation of several anionic and cationic organic pollutants

A series of Pb doped CeO2 nanocubes with seven different Pb loadings (2–12 mol%) were synthesized via modified hydrothermal technique. The prepared samples were characterized by XRD, XPS, FT-IR, TGA, SEM, HR-TEM, EDS and UV–Vis DRS analysis. According to XRD analysis, the crystalline structure of synthesized pure CeO2 and Pb-doped CeO2 samples are cubic structure. The ceria nanocubes showed an increase in amount of oxygen vacancies with increasing the dopant concentrations. When the doping level of Pb is 6 mol%, the optical band gap of Pb-CeO2 is smaller than that of pure CeO2 nanocubes. The HR-TEM results confirms the cubic structure of 6% Pb-CeO2 with average crystallite size of about 15 nm. The photocatalytic ability of Pb-CeO2 catalysts were studied by degrading several anionic and cationic organic pollutants like methylene blue (MB), methylene orange (MO), methylene red (MR), rhodamine B (RhB), reactive blue 160 (RB160), salicylic acid (SA), coumarin and phenol. The 6% Pb-CeO2 nanocubes shows better photocatalytic performance against anionic dyes especially for MB. To find the optimum condition for better photocatalytic performance of 6% Pb-CeO2 nanocubes, the photocatalytic process was conducted in different initial reaction conditions like reaction temperature, catalytic dosage, dye concentration and pH of the reaction solution. The stability and recyclability of 6% Pb-CeO2 photocatalyst was studied by XRD, FT-IR and EDS analysis after 5 cycles of MB degradation. The hydroxyl radical estimation and trapping experiments were conducted to observe the photocatalytic mechanism process in 6% Pb-CeO2 nanocubes. The perfect doping concentration for better organic pollutant degradation by Pb-CeO2 is found to be 6 mol% of Pb.

Efficiency of DMSO as hydroxyl radical probe in an Electrochemical Advanced Oxidation Process − Reactive oxygen species monitoring and impact of the current density

In electro-Fenton process, current density is a key operating parameter for organic compound mineralization. In order to explain mineralization yields obtained during the electrochemical treatment of an antibiotic metronidazole (MTZ) in a mono-compartment batch reactor, the evolution of the reactive oxygen species was discussed. Dissolved oxygen, Hydrogen peroxide and hydroxyl radical (OH) concentrations were followed during electrolysis performed at current intensities from 50 to 600mA corresponding to current densities from 0.04 to 0.45mAcm−2, using a three dimensional graphite felt as working electrode. Dimethylsulfoxide (DMSO) was used to trap hydroxyl radicals by the production of a stable intermediate, methanesulfonate; however the evolution of hydroxyl radical concentration was not in accordance with MTZ mineralization yields. Results showed that on the one hand, for the highest studied current densities, dissolved oxygen could become a limiting reagent for the OH quantification. On the other hand, DMSO can be oxidized and reduced at the electrodes surface. Indeed, Dimethyl sulfide (DMS), a byproduct from the electrochemical reduction of DMSO was detected during the electrolysis. DMSO appeared therefore relevant as a hydroxyl radical probe in the case of the electro-Fenton process only for low applied current densities, until 0.07mAcm−2 in the present study.

Heterogeneous catalytic oxidation of persistent chlorinated organics over cobalt substituted zinc ferrite nanoparticles at mild conditions: Reaction kinetics and catalyst reusability studies

This study explores the destructive removal of Persistent Organic Pollutants (POPs) like 2,4-dichlorophenol (DCP) and 2,4-dichlorophenoxy acetic acid (2,4-D) from water by wet peroxide oxidation method at ambient conditions using cobalt substituted zinc ferrite nanocomposites catalysts. The structural properties of catalysts were characterised by Fourier Transform Infra-Red spectroscopy (FTIR), Temperature Programmed Reduction (TPR- H2) and desorption (TPD- NH3 and TPD- CO2) techniques. TPR study revealed that the oxidation property of zinc ferrite composite increase with cobalt substitution. Complete removal of DCP and 2,4-D occurred within 90min over CoxZn1-xFe2O4 catalysts with 94.84%/75.60% and 83.5%/49.2% of removal of Chemical Oxygen Demand (COD)/Total Organic Carbon (TOC) respectively. The effect of reaction variables like reaction time, pollutant concentration, catalyst composition and its dosage, temperature and oxidant concentration on the removal efficiency was optimized. CoxZn1-xFe2O4 was found to be effective catalysts for destructive removal of pollutants and the composite with composition x-1.0 showed the highest activity. Atomic Absorption Spectrophotometry (AAS) proved the catalysts to be stable against leaching. The catalysts were reusable without any significant structural change as indicated by X-ray diffraction (XRD) and BET surface area studies. The active hydroxyl radical trapping experiments using n-butanol indicated a heterogeneous free radical mechanism.

Heterojunction construction between TiO2 hollowsphere and ZnIn2S4 flower for photocatalysis application

In the past few years, more and more efforts have been made on designing novel and efficient semiconductor-based heterojunction photocatalyst to maximize the capture and conversion efficiency of solar energy. In this work, unique TiO2 hollow sub-microspheres (THSs) and ZnIn2S4 (ZIS) flower-like microspheres were combined through a facile hydrothermal method and novelly applied in photocatalytic metronidazole (MTZ) degradation. The effects of THSs on the physicochemical properties and photocatalytic performance of ZIS were systemically investigated, and the optimal weight ratio of THS and ZIS in the composite was found. Furthermore, various technologies such as photoluminescence (PL), surface photovoltage spectra (SPS) and electrochemical impedance spectra (EIS) were used to verify the intimate contact and highly-efficient charge-carriers transfer between THS and ZIS components. The underlying photocatalysis mechanism was also carefully surveyed and proposed through hydroxyl radicals (OH) monitoring and radical trapping experiments.

Removal of AOX, Chroma and TOC in Chemical Dyestuff Wastewater with Iron Scraps-Fenton-Coagulation Combined Process

Iron scraps-Fenton-coagulation process was applied to chemical dyestuff wastewater. The removal performance of absorbable organic halogens(AOX), chroma and total organic carbon (TOC) was investigated at different molar ratios of Fe2+ to H2O2 (1:3-1:15), iron scraps reaction time (2-5 h) and Fenton reaction time (20-80 min). The results showed that the removal ratios of AOX, chroma and TOC firstly increased and then decreased with the decrease of the molar ratio of Fe2+ to H2O2, while continuously increased with the increase of iron scraps and Fenton reaction time. The optimal condition was determined as Fe2+:H2O2 ratio of 1:8, iron scraps reaction time of 4 h and Fenton reaction time of 60 min, under which 94.2% of AOX, 93.7% of chroma and 27.2% of TOC were removed. A comparison study revealed that the iron scraps-Fenton-coagulation combined process could achieve much better removal of AOX, chroma and TOC than any other single or combined processes of iron treatment, Fenton oxidation and coagulation. GC-MS analysis revealed that halogenated compounds and anilines were efficiently removed, as well as nitrobenzenes, phenols, benzaldehydes, ethers, nitriles and heterocyclic compounds.·OH was found to devote much in the Fenton reaction according to the tert-butyl alcohol trapping hydroxyl radicals test.