Photoassisted Fenton degradation of phthalocyanine dyes from wastewater of printing industry using Fe(Ⅱ)/γ-Al2O3 catalyst in up-flow fluidized-bed

Fe(II)/γ-Al2O3 powders synthesized using the dipping method were produced from a mixed aqueous solution containing aluminium oxide(γ-Al2O3) and iron(II)-precursor(FeSO4), and used for photoFenton degradation of phthalocyanine dyes(PCS) under ultraviolet(UV) irradiation in an up-flow fluidized bed. The catalysts were characterized by XRD, ESCA, BET, EDS and SEM. The results showed that Fe2+ion was compounded on the γ-Al2O3 carrier. The effects of different reaction parameters such as catalyst activity, dosage and solution pH on the decolorization of PCS were assessed. Results indicated that maximum decolorization(more than 95%) of PCS occurred with20 wt% Fe(II)/γ-Al2O3 catalyst(dosage of 60 g/L) using a combination of UV irradiation and heterogeneous Fenton system. The degradation efficiency of PCSincreases as pH decreases, exhibiting a maximum efficiency at pH 3.5. The recycled catalyst was capable of repeating three runs without a significant decrease in treatment efficiency, and this demonstrated the stability and reusability of catalyst.     

Removing lignin model pollutants with BiFeO3–g-C3N4 compound as an efficient visible-light-heterogeneous Fenton-like catalyst

BiFeO_3–g-C_3N_4 nanoscaled composite was prepared with a hydrothermal method and evaluated as a highly efficient photo-Fenton like catalyst under visible light irradiation. The BiFeO_3–g-C_3N_4 composite exhibited much stronger adsorption ability to lignin model pollutant(guaiacol) than that of BiFeO_3, which may be due to the higher specific surface area(BiFeO_3–g-C_3N_4: 35.59 m~2/g BiFeO_3: 7.42 m~2/g) and the adsorption form of π–π stack between g-C_3N_4 and guaiacol. The composite exhibited excellent visible light-Fenton like catalysis activity, being influenced by the solution pH value and the proportions of BiFeO_3 and g-C_3N_4 nanosheets. Under optimal conditions with visible light irradiation, the BiFeO_3–g-C_3N_4 composite yielded fast degradation of guaiacol with an apparent rate constant of 0.0452 min~(-1), which were 5.21 and 6.80 folds of that achieved by using BiFeO_3 and the mixture of BiFeO_3 and g-C_3N_4 nanosheets, respectively. The significantly enhanced visible light-Fenton like catalytic properties of the BiFeO_3–g-C_3N_4 composite in comparison with that of BiFeO_3 was attributed to a large surface area, much increased adsorption capacity and the semiconductor coupling effect between BiFeO_3 and g-C_3N_4 in the composite.     

Enhanced dechlorination of 2,4-dichlorophenol by recoverable Ni/Fe–Fe3O4 nanocomposites

Ni/Fe-Fe_3O_4 nanocomposites were synthesized for dechlorination of 2,4-dichlorophenol(2,4-DCP). The effects of the Ni content in Ni/Fe-Fe_3O_4 nanocomposites, solution pH, and common dissolved ions on the dechlorination efficiency were investigated, in addition to the reusability of the nanocomposites. The results showed that increasing content of Ni in Ni/Fe–Fe_3O_4 nanocomposites, from 1 to 5 wt.%, greatly increased the dechlorination efficiency; the Ni/Fe–Fe_3O_4 nanocomposites had much higher dechlorination efficiency than bare Ni/Fe nanoparticles. Ni content of 5 wt.% and initial p H below 6.0 was found to be the optimal conditions for the catalytic dechlorination of 2,4-DCP. Both 2,4-DCP and the intermediate product 2-chlorophenol(2-CP) were completely removed, and the concentration of the final product phenol was close to the theoretical phenol production from complete dechlorination of 20 mg/L of 2,4-DCP, after 3 hr reaction at initial p H value of 6.0,3 g/L Ni/Fe-Fe_3O_4 , 5 wt.% Ni content in the composite, and temperature of 22℃. 2,4-DCP dechlorination was enhanced by Cl-and inhibited by NO3-and SO_4~(2-). The nanocomposites were easily separated from the solution by an applied magnetic field. When the catalyst was reused, the removal efficiency of 2,4-DCP was almost 100% for the first seven uses, and gradually decreased to 75% in cycles 8–10. Therefore, the Ni/Fe–Fe_3O_4 nanocomposites can be considered as a potentially effective tool for remediation of pollution by 2,4-DCP.     

Photocatalytic properties of P25-doped TiO2 composite film synthesized via sol–gel method on cement substrate

TiO_2 films have received increasing attention for the removal of organic pollutants via photocatalysis. To develop a simple and effective method for improving the photodegradation efficiency of pollutants in surface water, we herein examined the preparation of a P25-TiO_2 composite film on a cement substrate via a sol–gel method. In this case, Rhodamine B(Rh B)was employed as the target organic pollutant. The self-generated TiO_2 film and the P25-TiO_2 composite film were characterized by X-ray diffraction(XRD), N_2 adsorption/desorption measurements, scanning electron microscopy(SEM), transmission electron microscopy(TEM), and diffuse reflectance spectroscopy(DRS). The photodegradation efficiencies of the two films were studied by Rh B removal in water under UV(ultraviolet) irradiation. Over 4 day exposure, the P25-TiO_2 composite film exhibited higher photocatalytic performance than the self-generated TiO_2 film. The photodegradation rate indicated that the efficiency of the P25-TiO_2 composite film was enhanced by the addition of the rutile phase Degussa P25 powder. As such, cooperation between the anatase TiO_2 and rutile P25 nanoparticles was beneficial for separation of the photo-induced electrons and holes. In addition, the influence of P25 doping on the P25-TiO_2 composite films was evaluated. We found that up to a certain saturation point, increased doping enhanced the photodegradation ability of the composite film. Thus, we herein demonstrated that the doping of P25 powders is a simple but effective strategy to prepare a P25-TiO_2 composite film on a cement substrate, and the resulting film exhibits excellent removal efficiency in the degradation of organic pollutants.     

Comparison between UV and VUV photolysis for the pre-and post-treatment of coking wastewater

In this study, ultraviolet(UV) and vacuum ultraviolet(VUV) photolysis were investigated for the pre-treatment and post-treatment of coking wastewater. First, 6-fold diluted raw coking wastewater was irradiated by UV and VUV. It was found that 15.9%–35.4% total organic carbon(TOC) was removed after 24 hr irradiation. The irradiated effluent could be degraded by the acclimated activated sludge. Even though the VUV photolysis removed more chemical oxygen demand(COD) than UV, the UV-irradiated effluent demonstrated better biodegradability. After 4 hr UV irradiation, the biological oxygen demand BOD5/COD ratio of irradiated coking wastewater increased from 0.163 to 0.224, and its toxicity decreased to the greatest extent. Second, the biologically treated coking wastewater was irradiated by UV and VUV. Both of them were able to remove 37%–47% TOC within 8 hr irradiation.Compared to UV, VUV photolysis could significantly improve the transparency of the bio-treated effluent. VUV also reduced 7% more ammonia nitrogen(NH+4–N), 17%more nitrite nitrogen(NO-2–N), and 18% more total nitrogen(TN) than UV, producing 35%less nitrite nitrogen(NO-3–N) as a result. In conclusion, UV irradiation was better in improving the biodegradability of coking wastewater, while VUV was more effective at photolyzing the residual organic compounds and inorganic N-species in the bio-treated effluent.     

Methyl Orange removal by a novel PEI-AuNPs-hemin nanocomposite

A novel poly(ethyleneimine)/Au nanoparticles/hemin nanocomposite(PEI-AuNPs-Hemin)acting for Methyl Orange(MO) removal has been synthesized. PEI-AuNPs was prepared firstly and it was then linked to hemin through the coupling between carboxyl groups in hemin and amino groups in PEI without the activation of carboxyl groups. The high reactivity and stability of AuNPs contributed greatly in the formation of the amido bonds in the nanocomposite. Fourier transform infrared spectroscopy, transmission electron microscopy and UV–visible spectroscopy were used to characterize the PEI-AuNPs-Hemin.Results show that PEI-AuNPs-Hemin has strong adsorption for MO. Adsorption and degradation experiments were carried out at different p Hs, nanocomposite concentrations and UV irradiation times. Removal of MO in acidic solutions was more effective than in basic solutions. The real-time study showed that the MO degradation with the nanocomposite under UV irradiation was a fast process. In addition, the photocatalytic degradation mechanism was proposed. The study suggests that the PEI-AuNPs-Hemin may have promising applications in environmental monitoring and protection.     

DBP formation from degradation of DEET and ibuprofen by UV/chlorine process and subsequent post-chlorination

The formation of disinfection by-products(DBPs) from the degradation of N,N-diethyl-3-methyl benzoyl amide(DEET) and ibuprofen(IBP) by the ultraviolet irradiation(UV)/chlorine process and subsequent post-chlorination was investigated and compared with the UV/H_2O_2 process.The pseudo first-order rate constants of the degradation of DEET and IBP by the UV/chlorine process were 2 and 3.1 times higher than those by the UV/H_2O_2 process, respectively, under the tested conditions. This was due to the significant contributions of both reactive chlorine species U(RCS) and hydroxyl radicals(HO) in the UV/chlorine process. Trichloromethane, 1,1,1-trichloro-2-propanone and dichloroacetic acid were the major known DBPs formed after 90% of both DEET and IBP that were degraded by the UV/chlorine process. Their yields increased by over 50%after subsequent 1-day post-chlorination. The detected DBPs after the degradation of DEET and IBP comprised 13.5% and 19.8% of total organic chlorine(TOCl), respectively, and the proportions increased to 19.8% and 33.9% after subsequent chlorination, respectively. In comparison to the UV/H_2O_2 process accompanied with post-chlorination, the formation of DBPs and TOCl in the UV/chlorine process together with post-chlorination was 5%–63% higher,Ulikely due to the generation of more DBP precursors from the attack of RCS, in addition to HO.     

Photocatalytic parameters and kinetic study for degradation of dichlorophenol-indophenol (DCPIP) dye using highly active mesoporous TiO2 nanoparticles

Highly active mesoporous TiO_2 of about 6 nm crystal size and 280.7 m~2/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized by means of XRD(X-ray diffraction), SEM(scanning electron microscopy), TEM(transmission electron microscopy), FT-IR(Fourier transform infrared spectroscopy), TGA(thermogravimetric analysis), DSC(differential scanning calorimetry) and BET(Brunauer–Emmett–Teller) surface area. The degradation of dichlorophenol-indophenol(DCPIP) under ultraviolet(UV) light was studied to evaluate the photocatalytic activity of samples. The effects of different parameters and kinetics were investigated. Accordingly, a complete degradation of DCPIP dye was achieved by applying the optimal operational conditions of 1 g/L of catalyst, 10 mg/L of DCPIP, pH of 3 and the temperature at 25 ± 3°C after 3 min under UV irradiation. Meanwhile, the Langmuir–Hinshelwood kinetic model described the variations in pure photocatalytic branch in consistent with a first order power law model.The results proved that the prepared TiO_2 nanoparticle has a photocatalytic activity significantly better than Degussa P-25.     

Synergistic effect of N-and F-codoping on the structure and photocatalytic performance of TiO2

Three types of Ti O2 nanostructures were synthesized via a facile hydrolysis method at195 °C. Effects of the preparation method and doping with N and F on the crystal structure and photocatalytic performance of Ti O2 were investigated. The nanomaterials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller porosimetry, ultraviolet–visible diffuse reflectance spectroscopy and fluorescent emission spectra. Their photo-catalytic activity was examined by the photodegradation of methylene blue in aqueous solution under both ultra-violet and visible light irradiation. The results show that nitrogen and fluorine co-doped anatase Ti O2 had the characteristics of a smaller crystalline size, broader light absorption spectrum and lower charge recombination than pure Ti O2. Most importantly, more efficient photocatalytic activity under both ultra-violet and visible light was observed. The obtained N–F-Ti O2 nanomaterial shows considerable potential for water treatment under sunlight irradiation.     

Highly selective catalytic reduction of NOxby MnOx–CeO2–Al2O3 catalysts prepared by self-propagating high-temperature synthesis

We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NOxwith NH3(NH_3-SCR).Using the catalyst with 18 wt.% Mn(18 MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr-1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18 MnCe1Al2 showed great resistance to SO_2(100 ppm)and H_2O(5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller(BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H_2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18 MnCe1Al2 has an extensive pore structure,with a BET surface area of approximately 135.4 m~2/g, a pore volume of approximately 0.16 cm~3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18 MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnOx–CeO_2–Al_2O_3 catalysts were good, and because of the simplicity of the preparation process,the SHS method is applicable to their industrial-scale manufacture.     

Photochemistry of insecticide imidacloprid: direct and sensitized photolysis in aqueous medium

The direct and sensitized photodegradations of imidacloprid, 1-(6-chloro-3-pyridinylmethyl)-N-nitro-2-imidazolidinimine, were investigated in aqueous solution and with and without various photo-sensitizers. Results of the study revealed that the intensity of lamp-house and irradiation wavelength had significant effects on the photolysis of imidacloprid. Complete degradation of 20 mg/L imidacloprid in aqueous phase was observed in 40 min under ultraviolet(UV) irradiation system, suggesting the ultraviolet ray played significant role in direct photolysis of imidacloprid. The additions of various photo-sensitizers lead to improve the degradation efficiency of imidacloprid under the irradiation of black light fluorescent lamp. TiO2 was the most efficient in the photo-catalytic degradation of imidacloprid among other photo-sensitizers in used this study. However, addition of acetone inhibited the photolysis of imidacloprid under the irradiation of UV, indicating the occurrence of competition between acetone and imidacloprid for photos. Mineralization of the imidacloprid was examined to clarify the final photochemical degradation products of the insecticide which were CO2, CI^- and NO3^-. Complete photo-oxidation of nitrogen to NO3^- occurred very slowlyvia the intermediate formation of NH4^ and NO2^- .     

Choice of precipitant and calcination temperature of precursor for synthesis of NiCo2O4 for control of CO–CH4 emissions from CNG vehicles

Compressed natural gas(CNG)is most appropriate an alternative of conventional fuel for automobiles.However,emissions of carbon-monoxide and methane from such vehicles adversely affect human health and environment.Consequently,to abate emissions from CNG vehicles,development of highly efficient and inexpensive catalysts is necessary.Thus,the present work attempts to scan the effects of precipitants(Na_2CO_3,KOH and urea)for nickel cobaltite(Ni Co_2O_4)catalysts prepared by co-precipitation from nitrate solutions and calcined in a lean CO-air mixture at 400°C.The catalysts were used for oxidation of a mixture of CO and CH_4(1:1).The catalysts were characterized by X-ray diffractometer,Brunauer–Emmett–Teller surface-area,X-ray photoelectron spectroscopy;temperature programmedreductionandScanningelectronmicroscopycoupledwith Energy-Dispersive X-Ray Spectroscopy.The Na_2CO_3was adjudged as the best precipitant for production of catalyst,which completely oxidized CO-CH_4mixture at the lowest temperature(T_(100)=350°C).Whereas,for catalyst prepared using urea,T_(100)=362°C.On the other hand the conversion of CO-CH_4mixture over the catalyst synthesized by KOH limited to 97%even beyond 400°C.Further,the effect of higher calcination temperatures of 500 and600°C was examined for the best catalyst.The total oxidation of the mixture was attained at higher temperatures of 375 and 410°C over catalysts calcined at 500 and 600°C respectively.Thus,the best precipitant established was Na_2CO_3and the optimum calcination temperature of 400°C was found to synthesize the Ni Co_2O_4catalyst for the best performance in CO-CH_4oxidation.     

Nano-sized Fe2O3/Fe3O4 facilitate anaerobic transformation of hexavalent chromium in soil–water systems

The purpose of this study is to investigate the effects of nano-sized or submicro Fe_2O_3/Fe_3O_4 on the bioreduction of hexavalent chromium(Cr(VI)) and to evaluate the effects of nano-sized Fe_2O_3/Fe_3O_4 on the microbial communities from the anaerobic flooding soil.The results indicated that the net decreases upon Cr(VI) concentration from biotic soil samples amended with nano-sized Fe_2O_3(317.1 ± 2.1 mg/L) and Fe_3O_4(324.0 ± 22.2 mg/L) within21 days,which were approximately 2-fold of Cr(VI) concentration released from blank control assays(117.1 ± 5.6 mg/L).Furthermore,the results of denaturing gradient gel electrophoresis(DGGE) and high-throughput sequencing indicated a greater variety of microbes within the microbial community in amendments with nano-sized Fe_2O_3/Fe_3O_4 than the control assays.Especially,Proteobacteria occupied a predominant status on the phylum level within the indigenous microbial communities from chromium-contaminated soils.Besides,some partial decrease of soluble Cr(VI) in abiotic nano-sized Fe_2O_3/Fe_3O_4 amendments was responsible for the adsorption of nano-sized Fe_2O_3/Fe_3O_4 to soluble Cr(VI).Hence,the presence of nano-sized Fe_2O_3/Fe_3O_4 could largely facilitate the mobilization and biotransformation of Cr(VI) from flooding soils by adsorption and bio-mediated processes.     

Nb_2O_5 nanowires in-situ grown on carbon fiber: A high-efficiency material for the photocatalytic reduction of Cr(Ⅵ)

Niobium oxide nanowire-deposited carbon fiber(CF) samples were prepared using a hydrothermal method with amorphous Nb_2O_5·nH_2O as precursor. The physical properties of the samples were characterized by means of numerous techniques, including X-ray diffraction(XRD), energy-dispersive spectroscopy(EDS), scanning electron microscopy(SEM), transmission electron microscopy(TEM), selected-area electron diffraction(SAED), UV–visible spectroscopy(UV–vis), N_2 adsorption–desorption, Fourier transform infrared spectroscopy(FT-IR), and X-ray photoelectron spectroscopy. The efficiency for the removal of Cr(VI) was determined.Parameters such as pH value and initial Cr(VI) concentration could influence the Cr(VI) removal efficiency or adsorption capacity of the Nb_2O_5/carbon fiber sample obtained after hydrothermal treatment at 160°C for 14 hr. The maximal Cr(VI) adsorption capacity of the Nb_2O_5 nanowire/CF sample was 115 mg/g. This Nb_2O_5/CF sample also showed excellent photocatalytic activity and stability for the reduction of Cr(VI) under UV-light irradiation: the Cr(VI) removal efficiency reached 99.9% after UV-light irradiation for 1 hr and there was no significant decrease in photocatalytic performance after the use of the sample for 10 repeated cycles. Such excellent Cr(VI) adsorption capacity and photocatalytic performance was related to its high surface area,abundant surface hydroxyl groups, and good UV-light absorption ability.     

Preparation of Ti species coating hydrotalcite by chemical vapor deposition for photodegradation of azo dye

TiO_2 in anatase crystal phase is a very effective catalyst in the photocatalytic oxidation of organic compounds in water. To improve its photocatalytic activity, the Ti-coating Mg Al hydrotalcite(Ti–Mg Al–LDH) was prepared by chemical vapor deposition(CVD) method.Response surface method(RSM) was employed to evaluate the effect of Ti species coating parameters on the photocatalytic activity, which was found to be affected by the furnace temperature, N2 flow rate and influx time of precursor gas. Application of RSM successfully increased the photocatalytic efficiency of the Ti–Mg Al–LDH in methylene blue photodegradation under UV irradiation, leading to improved economy of the process.According to the results from X-ray diffraction, scanning electron microscopy, Brunner–Emmet–Teller and Barrett–Joyner–Hallender, thermogravimetric and differential thermal analysis, UV–vis diffuse reflectance spectra analyses, the Ti species(TiO_2or/and Ti~(4+)) were successfully coated on the Mg Al–LDH matrix. The Ti species on the surface of the Ti–Mg Al–LDH lead to a higher photocatalytic performance than commercial TiO_2-P25. The results suggested that CVD method provided a new approach for the industrial preparation of Ti-coating Mg Al–LDH material with good photocatalytic performances.     

TiO2–PANI/Cork composite: A new floating photocatalyst for the treatment of organic pollutants under sunlight irradiation

A novel photocatalyst based on TiO_2–PANI composite supported on small pieces of cork has been reported. It was prepared by simple impregnation method of the polyaniline(PANI)–modified TiO_2 on cork. The TiO_2–PANI/Cork catalyst shows the unique feature of floating on the water surface. The as-synthesized catalyst was characterized by X-ray diffraction(XRD),scanning electron micrograph(SEM), transmission electron microscopy(TEM), thermogravimetric analysis(TGA), Fourier transform infrared spectroscopy(FT-IR), UV–vis diffuse reflectance spectra(UV–vis DRS) and the Brunauer–Emmett–Teller(BET) surface area analysis. Characterization suggested the formation of anatase highly dispersed on the cork surface. The prepared floating photocatalyst showed high efficiency for the degradation of methyl orange dye and other organic pollutants under solar irradiation and constrained conditions, i.e., no-stirring and no-oxygenation. The TiO_2–PANI/Cork floating photocatalyst can be reused for at least four consecutive times without significant decrease of the degradation efficiency.     

La/Ce-codoped Bi2O3 composite photocatalysts with high photocatalytic performance in removal of high concentration dye

A series of La/Ce-codoped Bi_2O_3 composite photocatalysts were fabricated via hydrothermal–calcination process. The as-prepared products were intensively characterized by some physicochemical characterizations like N_2 physical adsorption, X-ray powder diffraction(XRD), scanning electron microscope(SEM), transmission electron microscope(TEM), UV–Vis diffuse reflectance(UV–Vis DRS), Fourier transform infrared spectroscopy(FT-IR),photoelectrochemical measurements, and photoluminescence(PL) spectroscopy. The characterization results indicated that La and Ce doping induced obvious crystal phase transformation in Bi_2O_3, from monoclinic to tetragonal phase. La and Ce codoping also gave rise to the obvious synergetic effects, e.g., the lattice contraction of Bi_2O_3, the decrease of crystal size and the increase of surface area. The photocatalytic performance of the prepared catalysts was evaluated by removal of dye acid orange II with high concentration under visible light irradiation. Results showed that La/Ce-codoped Bi_2O_3 displayed much higher photocatalytic performance than that of bare Bi_2O_3, single La or Ce doped Bi_2O_3 samples. The superior photocatalytic activity was mainly attributed to the improved texture and surface properties and the synergistic effects of La and Ce codoping on suppressing the recombination of photo-generated electrons(e~-) and holes(h~+).     

A nanocomposite consisting of silica-coated magnetite and phenyl-functionalized graphene oxide for extraction of polycyclic aromatic hydrocarbon from aqueous matrices

In this study,graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe_3O_4@SiO_2@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons(PAHs) from water samples.The resulting microspheres(Fe_3O_4@SiO_2@GO-PEA) were characterized by Fourier transform-infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),CHNS elemental analysis,and vibrating sample magnetometry(VSM) techniques.The adsorbent possesses the magnetic properties of Fe_3O_4 nanoparticles that allow them easily to be separated by an external magnetic field.They also have the high specific surface area of graphene oxide which improves adsorption capacity.Desorption conditions,extraction time,amount of adsorbent,salt concentration,and pH were investigated and optimized.Following desorption,the PAHs were quantified by gas chromatography with flame ionization detection(GC-FID).The limits of detection(at an S/N ratio of 3) were achieved from 0.005 to0.1 μg/L with regression coefficients(R~2) higher than 0.9954.The relative standard deviations(RSDs) were below 5.8%(intraday) and 6.2%(inter-day),respectively.The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7%and 106.7%(with RSDs of 1.6%to 8.4%,for n = 3).The results indicated that the Fe_3O_4@SiO_2@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.     

Enhanced photocatalytic degradation of lindane using metal–semiconductor Zn@ZnO and ZnO/Ag nanostructures

To achieve enhanced photocatalytic activity for the degradation of lindane, we prepared metal–semiconductor composite nanoparticles (NPs). Zn@ZnO core–shell (CS) nanocomposites, calcined ZnO, and Ag-doped ZnO (ZnO/Ag) nanostructures were prepared using pulsed laser ablation in liquid, calcination, and photodeposition methods, respectively, without using surfactants or catalysts. The as-prepared catalysts were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet–visible (UV–vis) spectroscopy, and photoluminescence spectroscopy. In addition, elemental analysis was performed by energy dispersive X-ray spectroscopy. The obtained XRD and morphology results indicated good dispersion of Zn and Ag NPs on the surface of the ZnO nanostructures. Investigation of the photocatalytic degradation of lindane under UV–vis irradiation showed that Zn@ZnO CS nanocomposites exhibit higher photocatalytic activity than the other prepared samples. The maximum degradation rate of lindane was 99.5% in 40 min using Zn@ZnO CS nanocomposites. The radical trapping experiments verified that the hydroxyl radical (·OH) was the main reactive species for the degradation of lindane.     

Activity and hydrothermal stability of CeO2–ZrO2–WO3 for the selective catalytic reduction of NOx with NH3

A series of CeO_2–ZrO_2–WO_3(CZW)catalysts prepared by a hydrothermal synthesis method showed excellent catalytic activity for selective catalytic reduction(SCR)of NO with NH_3 over a wide temperature of 150–550°C.The effect of hydrothermal treatment of CZW catalysts on SCR activity was investigated in the presence of 10% H_2O.The fresh catalyst showed above 90% NO_x conversion at 201–459°C,which is applicable to diesel exhaust NO_x purification(200–440°C).The SCR activity results indicated that hydrothermal aging decreased the SCR activity of CZW at low temperatures(below 300°C),while the activity was notably enhanced at high temperature(above 450°C).The aged CZW catalyst(hydrothermal aging at 700°C for 8 hr)showed almost 80% NO_x conversion at 229–550°C,while the V_2O_5–WO_3/TiO_2 catalyst presented above 80% NO_x conversion at 308–370°C.The effect of structural changes,acidity,and redox properties of CZW on the SCR activity was investigated.The results indicated that the excellent hydrothermal stability of CZW was mainly due to the CeO_2–ZrO_2 solid solution,amorphous WO_3 phase and optimal acidity.In addition,the formation of WO_3 clusters increased in size as the hydrothermal aging temperature increased,resulting in the collapse of structure,which could further affect the acidity and redox properties.