Green synthesis of three-dimensional magnesium ferrite/titanium dioxide/reduced graphene from Garcinia mangostana extract for crystal violet photodegradation and antibacterial activity

In this study,three-dimensional porous magnesium ferrite/titanium dioxide/reduced graphene oxide(Mg Fe_2O_(4)-GM/TiO_(2)/rGO(MGTG))was successfully synthesized via green and hydrothermal-supported co-precipitation methods using the extract of Garcinia mangostana(G.mangostana)as a reducing agent.The characterization results indicate the successful formation of the nano/micro Mg Fe_(2)O_(4)(MFO)and TiO_(2) on the structure of the reduced graphene oxide(rGO),which can also act as efficient support,alleviating the agglomeration of the nano/micro MFO and TiO_(2).The synergic effects of the adsorption and photodegradation activity of the material were investigated according to the removal of crystal violet(CV)under ultraviolet light.The effects of catalyst dosage,CV concentration,and p H on the CV removal efficiency of the MGTG were also investigated.According to the results,the CV photodegradation of the MGTG-200 corresponded to the pseudo-first-order kinetic model.The reusability of the material after 10 cycles also showed a removal efficiency of 92%.This happened because the materials can easily be recollected using external magnets.In addition,according to the effects of different free radicals·O_(2)^(-),h^(+),and·OH on the photodegradation process,the photocatalysis mechanism of the MGTG was also thoroughly suggested.The antibacterial efficiency of the MGTG was also evaluated according to the inhibition of the Gram-positive bacteria strain Staphylococcus aureus(S.aureus).Concurrently,the antibacterial mechanism of the fabricated material was also proposed.These results confirm that the prepared material can be potentially employed in a wide range of applications,including wastewater treatment and antibacterial activity.

Remarkably Enhanced Photodegradation of Organic Pollutants by NH_(2)-UiO-66/ZnO Composite under Visible-Light Irradiation

Semiconductor photocatalysis is a novel highly efficient and low-cost method for removing organic pollutants from wastewater.However,the photoreduction performance of semiconductors on organic pollutants is limited due to the weak absorption of visible light caused by its wide band gap and low carrier utilization rate resulting from severe electron-holes recombination.In the present study,flower-like NH_(2)-UiO-66(NU66)/ZnO nanocomposites were prepared using a facile method and exhibited high efficiency under visible light driven photocatalysts.The X-ray diffractometer(XRD),scanning electron microscope(SEM),transmitor electron microscope(TEM),and X-ray photoelectron spectroscopy(XPS)were used to characterize the prepared samples,indicating that NU66/ZnO was successfully synthesized.The photocatalytic activity of the prepared NU66/ZnO nanocomposites was determined by measuring the photodegradation of methylene blue(MB)and malachite green(MG)under visible-light irradiation.The optimal nanocomposite loading of 5%wt NU66 to NU66/ZnO demonstrated the highest photocatalytic activity for the degradation of MB.The photocatalytic activity of a 5%NU66/ZnO composite was approximately 95-fold and 19-fold higher than that of NU66 and ZnO samples,respectively.The enhanced activity of the 5%wt NU66/ZnO nanocomposite was further confirmed through photoelectrochemical analysis.The formation of type II heterojunctions between the counterparts significantly suppressed recombination of the photogenerated charge carriers.Photocatalytic degradation experiments with different quenchers indicated that the effect of superoxide anion radicals(•O_(2)^(−))had a greater effect than the other scavengers.Additionally,the improved photocatalytic mechanism underlying the activity of NU66/ZnO nanocomposites was also explored.These findings establish a basis for development of MOF based heterojunction for photocatalytic organic pollution remediation.

Tuning interfacial charge transfer for efficient visible-light-driven photodegradation and simultaneous H_(2)evolution

The edge-graphitized carbon nitride(C_(3)N_(4)-C g)was prepared by secondary pyrolysis to construct ZnO/C_(3)N_(4)-C g(ZCN)type-Ⅱheterojunction photocatalyst via a facile sonication dispersion method,which achieved∼7.04-fold and∼18.3-fold enhanced visible-light-driven photocatalytic performance for refrac-tory micropollutant removal and simultaneous hydrogen(H_(2))evolution respectively compared to con-ventional ZnO/g-C_(3)N_(4)Step-scheme heterojunction.The apparent quantum efficiency of the ZCN_(0.4)het-erojunction reaches 0.92%(λ=420 nm).Such excellent performance stems from that the edge-graphene moieties stitched onto the interface of heterojunction extend light absorption to the full visible spec-trum,meanwhile,the built-in electric field generated during Fermi level alignment accompanying fa-vorable band-bending structure provides an effective pathway for the rapid migration of photoinduced electrons via the edge graphene channel to improve interfacial charge separation efficiency.Interestingly,the midgap states introduced in ZCN heterojunction could temporarily retain photoexcited electrons to effectively inhibit the in situ carrier recombination for improved photocatalytic H_(2)evolution.Moreover,ZCN/peroxymonosulfate system exhibited excellent anti-interference performance against complex water bodies under visible illumination due to the synergistic effect between the co-existing anions and organic matter.Meanwhile,the eco-friendly nature of the ZCN/peroxymonosulfate system showed no biotoxicity of reaction filtrate on cell proliferation after treatment,which avoided secondary contamination.Consid-ering the outstanding performance in photocatalysis,the ZCN system exhibits broad potential for practical applications in water pollution control and green energy production.

Mechanism study on UV-induced photodegradation of nonylphenol ethoxylates by intermediate products analysis

Photodegradation of nonylphenol ethoxylates （NPloEO） was investigated in laboratory scale under UV irradiation. The intermediate photodegradation products were analyzed by LC-ESI-MS. Three kinds of intermediate products including aldehydic compounds, carboxylic compounds and cyclohexanyl compounds were identified. Five main degradation routes involving the oxidation of the alkyl chain and ethoxylate unit, shortening of the alkyl chain and ethoxylate unit, hydrogenation of the benzene ring were proposed.

Photodegradation of acetochlor in water and UV photoproducts identified by mass spectrometry

The sunlight photodegradation half-lives of 20 mg/L acetochlor were 151, 154 and 169 days in de-ionized water, river water and paddy water, respectively. When exposed to ultraviolet (UV) light, acetochlor in aqueous solution was rapidly degraded. The half-lives were 7.1, 10.1, and 11.5 min in de-ionized water, river water and paddy water, respectively. Photoproducts of acetochlor were identified by gas chromatography/mass spectrometry(GC/MS) and found at least twelve photoproducts resulted from dechlorination with subsequent hydroxylation and cyclization processes. The chemical structures of ten photoproducts were presumed on the basis of mass spectrum interpretation and literature data. Photoproducts are identified as 2-ethyl-6-methylaniline; N,N-diethylaniline; 4,8-dimethyl-2-oxo-1,2,3,4- tetrahydroquino-line; 2-oxo-N-(2-ethyl-6-methylphenyl)-N-(ethoxymethyl)acetamide; N-(ethoxymethyl)-2′-ethyl-6′-methylformanilide;1-hydroxyacetyl-2-ethoxyl-7-ethylind ole; 8-ethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 4,8-dimethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 2-hydroxy-2′-ethyl-6′-methyl-N-(ethoxymethyl)acetanilide and a compound related to acetochlor. The other two photoproducts were detected by GC/MS although their chemical structure was unknown.

Enhanced photodegradation of phenolic compounds by adding TiO_2 to soil in a rotary reactor

Photodegradation ofpentachlorophenol （PCP） and p-nitrophenol （PNP） in soil was carried out in a designed rotary reactor, which can provide the soil particles with continually uniform irradiation, and on a series of thin soil layers. TiO2, as a kind of environmental friendly photocatalyst, was introduced to the soil to enhance the processes. Compared with that on the soil layers, photodegradation of PCP at initial concentration of 60 mg/kg was improved dramatically in the rotary reactor no matter whether TiO2 was added, with an increase of 3.0 times in the apparent first-order rate constants. The addition of 1 wt% TiO2 furthered the improvement by 1.4 times. Without addition of TiO2, PNP （initial concentration of 60 mg/kg） photodegradation rate in the rotary reactor was similar to that on the soil layers. When 1 wt% additional TiO2 was added, PNP photodegradation was enhanced obviously, and the enhancement in the rotary reactor was 2 times of that on the soil layers, which may be attributed to the higher frequency of the contact between PNP on soil particles and the photocatalyst. The effect of soil pH and initial concentrations of the target compounds on the photodegradation in the rotary reactor was investigated. The order of the degradation rate at different soil pH was relative to the aggregation of soil particles during mixing in the rotary reactor. Photodegradation of PCP and PNP at different initial concentrations showed that addition of TiO2 to enhance the photodegradation was more suitable for contaminated soil with higher concentration of PCP, while was effective for contaminated soil at each PNP concentration tested in our study.

Visible Light Induced Photodegradation and Phototoxicity of Phloxine B and Uranine

Ohjective To determine the visible light-induced photodegradation kinetics of two xanthene photosensitizers, phloxine B and uranine, in solution and on the surface of silica TLC plates, and to examine the phototoxicity of residues of degradation, which could provide valuable safety data on the two photosensitizers and other xanthene chemicals when applied in the environment. Methods UV-Vis absorption during photodegradation was monitored with a Unico 2102 spectrophotometer. Organic content of samples was measured with a Shimadzu TOC 4100. Phototoxicity tests were carried out using Saccharomyces cerevisiae with the methods modified from Daniels. Results When phloxine B and uraniue degraded in solution, their apparent rate constant k was 0.0019 and 0.0027 min^-1, respectively. The total organic carbon （TOC） content decreased by approximately 50% during the 8 h irradiation period, which led to a gradual decrease in phototoxicity of the residues. The photodegradation of photosensitizers on the surface of silica TLC plates was much faster than that in the solution. The apparent rate constant k and the half life of phloxine B were 0.0073 min^-1 and 95 min, respectively. Conclusion Visible light can rapidly induce photodegradation of phloxine B and uranine. The phototoxicity of residues is also decreased. The environmental risk of applications of phloxine B and uranine is minimal.

Photodegradation of 17α-Ethynylestradiol in Aqueous Solution with Nitzschiahantzschiana or Chlorella vulgaris and Fe^(3+)

The photodegradation of 17α-ethynylestradiol (EE2) induced by highpressure mercury lamp (λ≥313 nm, 250 W) in aqueous solution with algae (e. g.Nitzschia hantzschiana andChlorella vulgaris) and Fe3+ was ineestigated initially. The affecting factors on the photodegradation were studied and described in details, such as algae concentration, Fe3+, exposure time, and so on. The concentration of EE2 in distilled water was determined using fluorescence spectrophotometer. The photodegradation of EE2 in aqueous solution exposed to 250 W high-pressure mercury lamp was evident in the presence of algae and Fe3+. With the algae concentration increasing, photodegradation rate increased. Fe3+ could accelerate the photocatalytic degradation of EE2 in aqueous solution with algae. The colloidal ferric hydroxide particles that might have absorbed on the algae cells could enhance the photocatalytic degradation of EE2 by algae. The catalysis in photocatalytic degradation reaction mainly resulted from the active oxygen (H2O2,1O2 and ·OH) that was caused by algae and Fe3+ under 250 W HPML. In this paper, the mechanism of photocatalytic degradation of EE2 by algae and Fe3+ is discussed theoretically in details. Key words 17α-ethynylestradiol - photodegradation - high-pressure mercury lamp - Nitzschia hantzschiana - Chlorella vulgaris - Fe3+ CLC number X 131. 2 Foundation item: Supported by the Scientific Research Foundation of Wuhan Environmental Protection Bureau and the National Natural Science Foundation of China (20177017)Biography: Liu Xian-li (1965-), male, Ph. D candidate, Associate professor, research direction: environmental chemistry

Isolation and Characterization of Photodegradation Impurity in Budesonide Drug Product Using LC-MS and NMR Spectroscopy

Budesonide is a corticosteroid used for the treatment of asthma via various matrices and inhalation mechanisms. An unknown peak of Budesonide aqueous formulation has been investigated during stability study wherein the impurity level observed around 0.1% well below the threshold 0.5%. The approach to identify anonymous species was adopted as first to generate the impurity in sample, isolate, enrich and was subjected to LC-MS/MS and NMR for spectral studies. Based on the spectral data the anonymous species were identified as a “Lumibudesonide’’ ((5aR,5bS,5cS,6S,7aS,7bS,10aR,11aS,11bS)-6-hydroxy-7b-(2-hydroxyacetyl)-5b,7a-dimethyl-9-propyl 1,5a,5b,5c,6,7,7a,7b,10a,11,11a,11b dodecahydrocyclopenta[2'',3'']cyclopropa [1'',2'':3', 4']benzo [1',2':4,5]indeno [1,2-d][1,3]dioxol-5(2H)-one), which is observed in photolysis of Budesonide.

Photodegradation mechanism of two dyes: the influence of adsorption behavior on the novel TiO_2 particles

The relationship between adsorption behavior and photocatalytic mechanism of the two dyes was investigated. Adsorption isotherms showed that the adsorption of cationic pink FG was Langmuir type behavior, while the reactive brilliant red k-2G was Freundlich type behavior. The increasing pH favored the adsorption of FG but have little effect on the photodegradation. The increasing pH favored the adsorption and the photodegradation of k-2G. The presence of scavenger of h + vb and OH· radical potassium iodide inhibited the degradation of k-2G, free radicals scavenger tetranitromethane inhibited the photodegradation of FG. These results indicated that the photodegradation of FG mainly via free radicals in solution, and the photodegradation of k-2G was mainly on the catalysts surface or near the interface of solid and solution by react with h + vb and surface-bound OH·. The different effect of SO 2- 4, HCO - 3 on the adsorp tion and photodegradation of two dyes confirmed these results.

Photodegradation of nitroaromatic compounds in aqueous solutions in the UV/H_2O_2 process

Photodegradation of nitrobenzene and nitrophenols in aqueous solutions by means of UV/H2 O2 process was studied in the Rayox batch reactors. Three nitrophenol isomers were identified as main photoproducts in the irradiated NB aqueous solutions. The distribution of nitrophenol isomers follows the order p-〉 m-〉 o-nitrophenol. Other intermediates detected include nitrohydroquinone, nitrocatechol, catechol, benzoquinone, phenol, nitrate/nitrite ions, formic acid, glyoxylic acid, maleic acid, oxalic acid and some aliphatic ketones and aldehydes. The degradation of nitrobenzene and nitrophenols at initial stages follows the first-order kinetics and the decay rate constants for nitrobenzene（NB） are around l0^-3-10^-2 s^-1 and for nitrophenols are around 10^-2 s^-1. The decomposition of H2 O2 in the presence of NB and each nitrophenol isomers follows zero-order kinetics. The quantum yields at initial stages for NB decay were estimated around 0.30 to 0.36, and for NPs decay is around 0.31-0.54.

Influence of coexisting substances on the photodegradation behaviors of 17α-ethinylestradiol (EE_2) in the UV/H_2O_2 process

The batch photodegradation reactor was used to investigate the influence of the common coexisting substances in wastewater,such as H+,anions (HCO3-,Cl-and NO3-) and organic compounds (methanol and bisphenol A),on the photodegradation behaviors of EE2 in the UV/H2O2 process.The results indicated that the addition of coexisting substances can influence the photodegradation behaviors of EE2 and it also follows the first-order kinetics.The acidic (pH 2-4) and alkaline (pH 10-12) medium benefit the photodegradation of EE2,but the photodegradation rate constant of EE2 keeps almost constant in the pH value of 4-10.The addition of anions,such as HCO3-,Cl-and NO3-,can inhibit the photodegradation of EE2,and the rate constant has a negative linear relationship with the concentration of the anions.However,the reduction degrees vary with the anions kinds,and the inhibition effect of the three anions is in the order of HCO3->NO3->Cl-.Addition of 5 mg/L methanol and bisphenol A can reduce the photodegradation rate constant of EE2by 84.31% and 72%,respectively.By comparison,the retardant effect of methanol is much more evident.In the studied concentrations range,the photodegradation rate constant of EE2 is the unary quadratic function of the organic compounds concentrations.

Photodegradation of Methylene Blue in Natural Seawater

This paper reports the photochemical degradation of Methylene Blue(MB)in natural seawater(NSW).The photode-gradation reaction conformed to the first-order reaction kinetics with the rate constant 0.0158 min-1.MB was photochemically de-gradated faster under high-pressure mercury lamp(HPML)than under sunlight.When MB was in lower concentrations,salinitycould inhibit the photoreaction whereas MB in higher concentration,salinity could accelerate the photoreaction.Humid acid couldalso inhibit the photoreactions.Toxicity tests with marine phytoplankton Skeletonema costatum(Sk)and Heterosigma akashiwo Hada(Ha)showed decreased acute toxicity after photodegradation.

Photodegradation and Removal of Diclofenac by the Green Alga Nannochloropsis oculata

The emerging contaminants(ECs)are organic compounds including pharmaceuticals.These products are consumed in large quantities,favoring their continuous entrance to the environment and affecting the health of living beings.Diclofenac is a non-steroidal anti-inflammatory drug with analgesic properties of prolonged release.It is the commonest postoperative analgesic,and it is highly consumed without prescription.In recent years,the capability of microalgae to remove pharmaceuticals in water has been tested as a promising tool.In this work,the removal efficiency of diclofenac(16µg/mL)by the microalga Nannochloropsis oculata CCAP 186/7 was evaluated.The major nutrient concentrations in Bold’s Basal Medium were modified(nitrogen and carbon:50 and 100%of their original concentration)to know their effect in the removal of diclofenac.Drug degradation by light was also evaluated.The maximum removal capacity of diclofenac in the medium was 68.8%.The percentage of diclofenac adsorbed on the cell wall was between 6 and 12.7%.Around 23.6%of diclofenac was degraded by light after 18 days.N.oculata did not show growth inhibition due to the presence of diclofenac.The results obtained point to the promissory application of N.oculata as a bioremediation system for diclofenac removal.

Irradiation Effect on Photodegradation of Pure and Plasticized Poly (4-Methylstyrene) in Solid Films

The photodegradation of irradiated thin films of poly (para-methylstyrene) with 265 nm radiations in the presence of airand as a function of irradiation time has been studied using UV-VIS, fluorescence and FT-IR Spectroscopic techniques. The influence of phthalate and terephthalate plasticizers on stability of poly (para-methylstyrene) towards irradiations was also investigated. Blending with phthalate plasticizers was found to cause a higher efficiency of photodegradation than that obtained in doping with terephthalate plasticizers. The intensity of absorption was also found to increase with time of irradiation and in change in the shape of the spectra at longer wavelength, thus indicating a possibility of photodegradation of polymer chains. The analysis of the FT-IR spectra of the irradiated and non-irradiated samples, shows a predominant absorption associated with carbonyl compounds with 1740 cm-1. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra, have provided an evidence for the photodegradation as well as photo-oxidation of polymeric chains. The presence of the plasticizer in the polymer backbone was found to accelerate the photodegradation of polymeric chains.

Theoretical Study on the Photodegradation Mechanism of Pyrethroid Insecticide Fenvalerate in Water

The photodegradation mechanism of fenvalerate in water has been investigated by density functional theory（DFT）.The geometries of reactants,transition states,intermediates and products are optimized at the B3LYP/6-31G＊ level.The calculated results indicate that the reaction process mainly includes the nucleophilic attack and the substitution reaction by hydroxyl radical to the carbonyl group.By vibrational frequency analysis and intrinsic reaction coordinate（IRC） method,the transition state and its reaction pathway are confirmed.Moreover,the changes of natural population analysis（NPA）,calculated using the Natural bond orbital（NBO） method,are analyzed along with the degradation reaction which can explain the variation of chemical bonds.Additionally,the solvent effect is also investigated and the results show that the reaction preferably takes place in water.

Quantitative Models for the Structure and Photodegradation of Polycyclic Aromatic Hydrocarbons

Based on the quantum chemical descriptors,quantitative structure-property relationship（QSPR） models have been developed to estimate and predict the photodegradation rate constant（logK） of polycyclic aromatic hydrocarbons（PAHs） by use of linear method（multiple linear regression,MLR） and non-linear method（back propagation artificial neural network,BP-ANN）.A BP-ANN with 3-3-1 architecture was generated by using three quantum chemical descriptors appearing in the MLR model.The standard heat of formation（HOF）,the gap of frontier molecular orbital energies（ΔELH） and total energy（TE） were inputs and its output was logK.Leave-One-Out（LOO） Cross-Validated correlation coefficient（R^2CV） of the established MLR and BP-ANN models were 0.6383 and 0.7843,respectively.The nonlinear BP-ANN model has better predictive ability compared to the linear MLR model with the root mean square error（RMSE） for training and validation sets to be 0.1071,0.1514 and the squared correlation coefficient（R^2） of 0.9791,0.9897,respectively.In addition,some insights into the molecular structural features affecting the photodegradation of PAHs were also discussed.

Dependence of bisphenol A photodegradation on the initial concentration of oxalate in the lepidocrocite-oxalate complex system

To understand the degradation of endocrine disrupting chemicals （EDCs） in natural environment with existence of iron oxides and carboxylic acids, the dependence of bisphenol A （BPA） photodegradation on the initial concentration of oxalate （Cox） in lepidocrocite （y-FeOOH） aqueous suspension was investigated under both UV and visible lights in this study. Lepidocrocite powder was home-prepared by a hydrothermal process. It was found that BPA degradation was promoted greatly in the presence of oxalate owing to the formation of lepidocrocite-oxalate complex. And there was an optimal Cox, which was 2.0 and 2.4 mmol/L, under UV and visible lights, respectively. The first-order kinetic constant, k value increased 38 times from 0.17 × 10^-2 min^-1 in the absence of oxalate to 6.39 × 10^-2 min^-1 in the presence of oxalate with an optimal Cox （2.0 mmol/L） under UV irradiation, and almost 306 times from 0.02 × 10^-2 min^-1 in the absence of oxalate to 6.11 × 10^-2 min^-1 in the presence of oxalate with an optimal Cox （2.4 mmol/L） under visible irradiation. The BPA degradation rate increased and the first-order kinetic constants decreased with the increase in BPA initial concentration. The dependence of the variation of pH value, total-Fe and Fe^2＋ during the photoreaction on Cox was also investigated. The pH value increased obviously with the reaction time. Total-Fe increased dramatically at the first 5 min and then decreased quickly under UV irradiation and slowly under visible irradiation. The initial concentration of oxalate is a main factor to affect BPA photodegradation in aqueous suspension under both UV and visible lights.