Synergism of solar-driven interfacial evaporation and photo-Fenton Cr(Ⅵ) reduction by sustainable Bi-MOF-based evaporator from waste polyester

The integration of interfacial solar steam generation and photocatalytic degradation technology has pro-vided a promising platform to simultaneously produce freshwater and degrade pollutants.However,con-structing low-cost,multi-functional evaporators for treating Cr(Ⅵ)-polluted water remains challenging,and the synergistic mechanism on Cr(Ⅵ)reduction is fuzzy.Herein,we propose the combined strategy of ball milling and solution mixing for the sustainable production of Bi-MOF microrod from waste poly(ethylene terephthalate),and construct Bi-MOF-based solar evaporators for simultaneous photo-Fenton Cr(Ⅵ)reduction and freshwater production.Firstly,the evaporator comprised of Bi-MOF microrod and graphene nanosheet possesses high light absorption,efficient photothermal conversion,and good hydro-philic property.Attributing to the advantages,the hybrid evaporator exhibits the evaporation rate of 2.16 kg m^(-2) h^(-1) and evaporation efficiency of 87.5%under 1 kW m^(-2) of irradiation.When integrating with photo-Fenton reaction,the Cr(Ⅵ)reduction efficiency is 91.3%,along with the reaction kinetics of 0.0548 min^(-1),surpassing many advanced catalysts.In the outdoor freshwater production and Cr(Ⅵ)reduction,the daily accumulative water yield is 5.17 kg m^(-2) h^(-1),and the Cr(Ⅵ)reduction efficiency is 99.9%.Furthermore,we prove that the localization effect derived from the interfacial solar-driven evap-oration enhances H_(2)O_(2) activation for the photo-Fenton reduction of Cr(Ⅵ).Based on the result of density functional theory,Bi-MOF microrod provides rich active centers for H_(2)O_(2) activation to produce active sites such as e-or-O_(2).This study not only proposes a new strategy to construct multi-functional solar evaporators for freshwater production and catalytic reduction of pollutants,but also advances the chem-ical upcycling of waste polyesters.

Reduction of Cr(Ⅵ) with a relative high concentration using different kinds of zero-valent iron powders: Focusing on effect of carbon content and structure on reducibility

Reduction of Cr(VI)using zero-valent iron(ZVI)could not only decrease the amounts of chemicals used for reduction,but also decrease the discharge of sludge.In order to find a desirable ZVI material,reduction of Cr(VI)with a relative high concentration using different kinds of ZVI powders(mainly carbon differences)including reduced Fe,grey cast iron,pig iron,nodular pig iron was carried out.Parameters such as ZVI dosage,type and size affecting on Cr(VI)reduction were firstly examined and grey cast iron was selected as a preferable reducing material,followed by pig iron.Additionally,it was found that the parameters had significant influences on experimental kinetics.Then,morphology and composition of the sample before and after reaction were characterized by SEM,EPMA and XPS analyses to disclose carbon effect on the reducibility.In order to further interpret reaction mechanism,different reaction models were constructed.It was revealed that not only the carbon content could affect the Cr(VI)reduction,but also the carbon structure had an important effect on its reduction.

Facile fabrication of ZnIn2S4/SnS2 3D heterostructure for efficient visible-light photocatalytic reduction of Cr（Ⅵ）

Photocatalytic method has been intensively explored for Cr(VI)reduction owing to its efficient and environmentally friendly natures.In order to obtain a high efficiency in practical application,efficient photocatalysts need to be developed.Here,ZnIn2S4/SnS2 with a three-dimensional(3D)heterostructure was prepared by a hydrothermal method and its photocatalytic performance in Cr(VI)reduction was investigated.When the mass ratio of SnS2 to ZnIn2S4 is 1:10,the ZnIn2S4/SnS2 composite exhibits the highest photocatalytic activity with 100%efficiency for Cr(VI)(50 mg/L)reduction within 70 min under visible-light irradiation,which is much higher than those of pure ZnIn2S4 and SnS2.The enhanced charge separation and the light absorption have been confirmed from the photoluminescence and UV-vis absorption spectra to be the two reasons for the increased activity towards photocatalytic Cr(VI)reduction.In addition,after three cycles of testing,no obvious degradation is observed with the 3D heterostructured ZnIn2S4/SnS2,which maintains a good photocatalytic stability.

Enhanced photocatalytic Cr(Ⅵ) reduction and diclofenac sodium degradation under simulated sunlight irradiation over MIL-100(Fe)/g-C_3N_4 heterojunctions

Metal‐organic framework MIL‐100(Fe)and g‐C3N4 heterojunctions(MG‐x,x=5%,10%,20%,and 30%,x is the mass fraction of MIL‐100(Fe)in the hybrids)were facilely fabricated through ball‐milling and annealing,and characterized by powder X‐ray diffraction,Fourier transform infrared spectroscopy,thermogravimetric analysis,transmission electron microscopy,UV‐visible diffuse‐reflectance spectrometry,and photoluminescence emission spectrometry.The photocatalytic activities of the series of MG‐x heterojunctions toward Cr(VI)reduction and diclofenac sodium degradation were tested upon irradiation with simulated sunlight.The influence of different organic compounds(ethanol,citric acid,oxalic acid,and diclofenac sodium)as hole scavengers and the pH values(2,3,4,6,and 8)on the photocatalytic activities of the series of MG‐x heterojunctions was investigated.MG‐20%showed superior photocatalytic Cr(VI)reduction and diclofenac sodium degradation performance than did the individual MIL‐100(Fe)and g‐C3N4 because of the improved separation of photoinduced electron‐hole charges,which was clarified via photoluminescence emission and electrochemical data.Moreover,the MG‐x exhibited good reusability and stability after several runs.

Bifunctional TiO2 Catalysts for Efficient Cr（VI） Photoreduction Under Solar Light Irradiation Without Addition of Acids

Bifunctional TiO2 photocatalysts co-doped with nitrogen and sulfur were prepared by the controlled thermal decomposition of ammonium titanyl sulfate precursor. They have both photocatalytic activity and Brφnsted acidity, and thus are active in the photoreduction of Cr（VI） under solar light irradiation without the addition of acids. The activity is superior to that of Degussa P25 in the acidified suspension at the same pH adjusted by H2SO4.

Influences of Organic Acids and Heavy Metals on Cr（VI） Photoreduction Catalyzed by TiO2 Suspension

Photocatalytic reduction of Cr（VI） by TiO2 suspension has been studied with the purpose of removing the toxic and carcinogenic Cr（VI） ions from water. The photocatalytic reduction was carried out in batch reactor, in which the influences of the presence ofmalonic and oxalic acids as well as of iron and lead ions on the degree of the reduction have been systematically evaluated. The results of the research indicated that the presence of malonic and oxalic acids with increasing concentration can improve the photoreduction. The increase in the Cr（V1） photoreduction is due to OH radical capturing by the organic acids so that it prevents the recombination of the OH radical and the free electron, and therefore can provide enough electron supply for Cr（VI） photoreduction. The effectiveness of Cr（VI） photoreduction is also enhanced by the addition of increasing concentration of both Fe（Ⅲ） and Pb（Ⅱ） ions through synergic effect. It is also found that the degree of the photopreduction is strongly influenced by solution acidity and the most effective Cr（VI） photoreduction is obtained at lower pH than 5, either in the absence or presence of the organic acids and the heavy metal ions.

Effect ofαphase morphology on fatigue crack growth behavior of Ti−5Al−5Mo−5V−1Cr−1Fe alloy

Taking a Ti−5Al−5Mo−5V−1Cr−1Fe alloy as exemplary case,the fatigue crack growth sensitivity and fracture features with various tailoredαphase morphologies were thoroughly investigated using fatigue crack growth rate(FCGR)test,optical microscopy(OM)and scanning electron microscopy(SEM).The tailored microstructures by heat treatments include the fine and coarse secondaryαphase,as well as the widmanstatten and basket weave features.The sample with coarse secondaryαphase exhibits better comprehensive properties of good crack propagation resistance(with long Paris regime ranging from 15 to 60 MPa·m1/2),high yield strength(1113 MPa)and ultimate strength(1150 MPa),and good elongation(11.6%).The good crack propagation resistance can be attributed to crack deflection,long secondary crack,and tortuous crack path induced by coarse secondaryαphase.

Solvent extraction of V(Ⅴ) and Cr(Ⅲ) from acidic leach liquors of ilmenite using Aliquat 336

Extraction of V（V） and Cr（III） from acidic sulfate leach liquors of ilmenite using 0.4 mol/L Aliquat 336 chloride in kerosene was carried out. Different parameters affecting the extraction process such as equilibrium time, sulfate concentration, Aliquat 336 concentration, equilibrium p H and the extraction temperature were investigated. Extraction of V（V） and Cr（III） by Aliquat 336 involved anion exchange mechanism, and the extracted species are [（VO2SO4）R4N]org at low equilibrium p H for V（V） and [R4N-Cr（OH）4]org at high equilibrium p H for Cr（III）. Calculated thermodynamic parameters show that the extraction process is endothermic reaction for V（V） and exothermic for Cr（III）. Also, calculated values of ？Gex and ？Sex indicate that the extraction reactions of V（V） and Cr（III） proceed as non-spontaneous reaction is more random. V（V） and Cr（III） were stripped, precipitated, separated and calcined at 500 °C for 2.0 h to produce the corresponding oxide in pure form after rinsing and drying.

Br-doping of g-C3N4 towards enhanced photocatalytic performance in Cr(Ⅵ)reduction

Semiconductor photocatalytic technology is widely recognized as one of the most promising technologies to solve current energy and environmental crisis, due to its ability to make effective use of solar energy. In recent years, graphite carbon nitride(g-C3N4), a new type of non-metallic polymer semiconductor photocatalyst, has rapidly become the focus of intense research in the field of photocatalysis because of its suitable bandgap energy, unique structure, and excellent chemical stability. In order to improve its intrinsic shortages of small specific surface area, narrow visible light response range, high electron-hole pair recombination rate, and low photon quantum efficiency, a simple method was utilized to synthesize Br-doped g-C3N4(CN–Br X, X = 5, 10, 20, 30), where X is a percentage mole ratio of NH4 Br to melamine. Experimental results showed that Br atoms were doped into the g-C3N4 lattice by replacing the bonded N atoms in the form of C–N=C, while the derived material retained the original framework of g-C3N4. The interaction of Br element with the g-C3N4 skeleton not only broadened the visible-light response of g-C3N4 to 800 nm with an adjustable band gap, but also greatly promoted the separation efficiency of the photogenerated charge carrier and the surface area. The photocurrent intensity of bare CN and CN–Br X(X = 5, 10, 20, 30) catalysts is calculated to be 1.5, 2.0, 3.1, 6.5, and 1.9 μA, respectively. And their specific surface area is measured to be 9.086, 9.326, 15.137, 13.397, and 6.932 m2/g. As a result, this Br-doped g-C3N4 gives significantly enhanced photocatalytic reduction of Cr(VI), achieving a twice enhancement over g-C3N4, with high stability during prolonged photocatalytic operation compared to bare g-C3N4 under visible light irradiation. Furthermore, an underlying photocatalytic reduction mechanism was proposed based on control experiments using radical scavengers.

S-Scheme photocatalyst TaON/Bi_(2)WO_(6) nanofibers with oxygen vacancies for efficient abatement of antibiotics and Cr(VI):Intermediate eco-toxicity analysis and mechanistic insights

Enlightened by natural photosynthesis,developing efficient S-scheme heterojunction photocatalysts for deleterious pollutant removal is of prime importance to restore environment.Herein,novel TaON/Bi_(2)WO_(6) S-scheme heterojunction nanofibers were designed and developed by in-situ growing Bi_(2)WO_(6) nanosheets with oxygen vacancies(OVs)on TaON nanofibers.Thanks to the efficiently spatial charge disassociation and preserved great redox power by the unique S-scheme mechanism and OVs,as well as firmly interfacial contact by the core-shell 1D/2D fibrous hetero-structure via the in-situ growth,the optimized TaON/Bi_(2)WO_(6) heterojunction unveils exceptional visible-light photocatalytic property for abatement of tetracycline(TC),levofloxacin(LEV),and Cr(Ⅵ),respectively by 2.8-fold,1.0-fold,and 1.9-fold enhancement compared to the bare Bi_(2)WO_(6),while maintaining satisfactory stability.Furthermore,the systematic photoreaction tests indicate Ta-ON/Bi_(2)WO_(6) has the high practicality in the elimination of pollutants in aquatic environment.The degradation pathway of tetracycline and intermediate eco-toxicity were determined based on HPLC–MS combined with QSAR calculation,and a possible photocatalytic mechanism was elucidated.This work provides a guideline for designing high-performance TaON-based S-scheme photocatalysts with defects for environment protection.

Room-temperature solid phase surface engineering of BiOI sheets stacking g-C_(3)N_(4) boosts photocatalytic reduction of Cr(Ⅵ)

Cr(Ⅵ)-based compounds pollution have attracted global concern due to serious harm to humans and environment.Hence,it is crucial to exploit an effective technique to eliminate Cr(Ⅵ)in water.Herein,we in-situ grown BiOI on graphitic carbon nitride to prepare the BiOI/g-C_(3)N_(4)(BCN)direct Z-scheme heterojunction by solid phase engineering method at room temperature.Experimental result shown the photocatalytic activity of pure BiOI were obviously enhanced by constructing Z-scheme BCN heterostructure,and BCN-3 heterostructure exhibited the optimal photocatalytic degradation of RhB with 98%yield for 2.5 h and reduction of Cr(Ⅵ)with more than 99%yield for 1.5 h at pH=2.Stability test shows BCN-3 still kept more than 98%reduction efficiency after 6 cycles.In addition,we also studied the reduction mechanism that shown the.O_(2)^(-)radicals essentially helped to reduce the Cr(Ⅵ)in aqueous solution under illumination,verified the direct Z-scheme charge transfer path by X-ray photoelectron spectroscopy(XPS)and the free radical trapping experiment.The work open a new way for rationally designing photocatalyst heterostructure to reduce Cr(Ⅵ)to Cr(Ⅲ).

Synthesis and Electrochemical Properties of Cr-doped Li_3V_2(PO_4)_3 Cathode Materials for Lithium-ion Batteries

Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram （CV）, and electrochemical impedance spectra（EIS）. The optimal doping content of Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.

Characterization of Cr(Ⅵ) resistance and reduction by Pseudomonas aeruginosa

The experiments were conducted to evaluate the Cr(Ⅵ)resistance and reduction by Pseudomonas aeruginosa.After this bacterium tolerated 40 mg/L Cr(Ⅵ),the growth of cells was observed.The bacterial growth was obviously lower than the controls over 24 h and the binary cell fission was observed in cell morphology by scanning electron microscope.P.aeruginosa was found to be able to reduce Cr(Ⅵ)although Cr(Ⅵ)had toxic effects on the cells.The results demonstrate that Cr(Ⅵ)is reduced from 40 mg/L to about 18 mg/L in 72 h.The value of pH drops from 7.02 to around 5.65 after 72 h.A significant increase in the value of redox potential occurs during Cr(Ⅵ)reduction and Cr(Ⅵ)reduction can be observed over a range of redox potential from+3 mV to+91 mV.Both of SO4 2-and NO3 -have no effect on Cr(Ⅵ)reduction.The presence of Zn 2+has a notable inhibitory effect on Cr(Ⅵ) reduction while Cu 2+ substantially stimulates Cr(Ⅵ)reduction.In the presence of Zn 2+ ,Cr(Ⅵ)decreases from 40 mg/L to only 26-27 mg/L,whereas Cr(Ⅵ)drops to 1-2 mg/L after 48 h in the presence of Cu2 +.

Selective removal of Cr(Ⅵ)using polyvinylpyrrolidone and polyacrylamide co-modified MoS_(2) ccomposites by adsorption combined with reduction

Cr(Ⅵ),one of the most hazardous metal pollutants,poses significant threats to the environment and human health.Herein,a novel MoS_(2) composite(MoS_(2)/PVP/PAM)modified by polyvinylpyrrolidone(PVP)and polyacrylamide(PAM)was synthesized to enhance the removal of Cr(Ⅵ).Characterization analysis including SEM,XRD,FTIR,and XPS indicated that PVP and PAM could increase the interlayer spacing and the dispersibility of MoS_(2),and introduce pyrrolic N and amino functional groups.The batch experiments showed that MoS_(2)/PVP/PAM represented excellent Cr(Ⅵ)removal performance over a wide p H range,and exhibited a significantly higher maximum Cr(Ⅵ)adsorption capacity(274.73 mg/g,at p H 3.0,and 298 K)than pure MoS_(2).The adsorption of Cr(Ⅵ)followed Langmuir and pseudo-second-order kinetic model,which was a homogeneous monolayer chemisorption process.MoS_(2)/PVP/PAM showed stable removal of Cr(Ⅵ)in the presence of humic acid(HA),interfering cations and anions at different concentrations.Moreover,it had excellent selectivity for Cr(Ⅵ)(K_(d) value of 1.69×10^(7)m L/g)when coexisting with a variety of competing ions.Multiple characterization revealed that Cr(Ⅵ)was reduced to low toxicity Cr(Ⅲ)by Mo^(4+)and S^(2-),and then chelated on the surface of the adsorbent by pyrrolic N.This research expanded the design concept for MoS_(2) composites by demonstrating the potential of MoS_(2)/PVP/PAM as a promising material for selective elimination of Cr(Ⅵ)in water.

Effects of V and Cr Addition on the Structural and Sensing Properties of Titania

We have comparatively studied the addition of Cr and V in titania.Cr and V content were changed by means of insets placed in the Ti target.Structural,compositional and electrical analyses of different series of thin films,made by XRF, XRD,are presented.Electrical characterization not only showed that Cr doped layers were very sensitive to ethanol within a useful range for applications,but also allowed to verify that the electrical behaviour is dependent on the structure of film. Finally,the Cr and V concentrations that gives the best results in terms of sensing performances has been determined and a correlation between structural and electrical measurement has been evidenced.

Tribological behavior of CrN-coated Cr–Mo–V steels used as die materials

DIN 1.2343 and 1.2367 steels are commonly used as die materials in aluminum extrusion, and single/duplex/multi-coatings enhance their surface properties. The design of an appropriate substrate/coating system is important for improving the tribological performance of these steels under service conditions because the load-carrying capacity of the system can be increased by decreasing the plastic deformation of the substrate. In this study, the tribological behavior of CrN-coated Cr–Mo–V steels(DIN 1.2343, 1.2367, and 1.2999 grades) was investigated using different setups and tribological pairs at room and elevated temperatures. The aim of this study was to reveal the wear resistance of a suggested system(1.2999/CrN) not yet studied and to understand both the wear and the failure characteristics of coated systems. The results showed that(i) among the steels studied, the DIN 1.2999 grade steel exhibited the lowest friction coefficient because it had the highest load-carrying capacity as a result of secondary hardening at elevated temperatures;(ii) at room temperature, both abrasive tracks and adhesive layers were observed on the worn surfaces; and(iii) a combination of chemical reactions and progressive oxidation caused aluminum adhesion on the worn surface, and the detachment of droplets and microcracking were the characteristic damage mechanisms at high temperatures.

IN-SITU OBSERVATION OF THERMAL FATIGUE CRACK GROWTH IN STEEL 3Cr2W8V

The growing process of thermal fatigue cracking,in steel 3Cr2WSV was observed under desk SEM fitted with sell-made minisized device for thermal faligue test.Before the growing of thermal fatigue crack,the main crack tip reveals to blunt firstly,and some holes and uncontinuous microcraeks occur in front of it.The growth is developed by bridging of main crack together with holes and microcracks.

Dynamic Model of Thermal Fatigue Crack Propagation In 3Cr2W8V Steel

In this paper, the thermal fatigue test data in 3Cr2W8V steel are analyzed numerically. Then, on this basis a formula of thermal fatigue crack propagation rate with respect to stress intensiyt factor range is presented. Finally a dynamic equation of the control parameters for thermal fatigue crack propagationis derived according to evaluating the thermal strain relaxation property of the steel.

Catalytic Dehydrogenation of n-Butane over V/SiO_2 Catalyst: A Comparison with Cr/SiO_2 Catalyst

V/SiO2 catalysts compared to Cr/SiO2 catalysts were studied for dehydrogenation of n-butane to butenes. Several methods for characterization of catalysts such as FT-IR, UV-vis and Raman spectroscopies were used. Some differences between two catalysts were showed, including the performances of catalysts, distribution of products and mechanism of reactions. The results showed that prepared catalysts with 12m% of active component loading all demonstrated best conversion of n-butane to butene at a reaction temperature of around 590 ℃. Two different reaction mechanisms were mentioned to well explain why iso-butene was produced on V/SiO2 catalysts but not on Cr/SiO2 catalysts.