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This work explores the impact of reaction temperature during thermal exfoliation treatment of bulk-g-C3N4 in the air atmosphere on the structure and performance of the resulting CN photocatalyst. The analysis conducted using XRD, FT-IR, XPS, SEM, and elements mapping tests, illustrated an increase in nitrogen-vacancy and oxygen content on the surface of the CN photocatalyst, resulting in a porous and sparse structure, changes in crystal size, and improved visible light absorption performance. The photocatalytic reduction experiments of hexavalent chromium (Cr(VI)) showed that the CN-540 showed the highest reduction rate of 96.9%, with a reaction rate constant 6.21 times that of bulk-g-C3N4. After 100 min of illumination, the photocatalytic degradation rates of CN-540 for TC-HCl and RhB were 66.7% and 60.6%, respectively. The TOC test results indicated mineralization rates of 51.5% for TC-HCl and 46.6% for RhB. Room temperature fluorescence spectroscopy (PL), transient photocurrent response (TPC), and electrochemical impedance spectroscopy (EIS) measurements confirmed the excellent photogenerated charge carrier separation and transport efficiency of CN-540. The photocatalytic mechanism for reducing Cr(VI) by CN-540 was elucidated based on the active species •OH and •O2 - and Mott-Schottky (M-S) tests. This study provides experimental data for optimizing the photocatalytic performance of g-C3N4 and paves a new way for developing efficient photocatalysts. [ABSTRACT FROM AUTHOR]

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In this work, TiO2-based composite photocatalysts were synthesized for the photoreduction of Cr(VI) by deposition of CdS and/or Cu nanoparticles. Oak leaf extract was used as a reducing agent for the synthesis of Cu nanoparticles. Although the deposited amount of Cu was small (~ 1.1 wt%), it resulted in a shift of the absorption edge to the visible region and a significantly higher efficiency compared to TiO2. Deposition of ~ 3 wt% CdS resulted also in a higher activity under the visible light compared to TiO2, but lower compared to Cu-TiO2. The best results were obtained with the ternary photocatalyst, probably due to the formation of a z-scheme in which the deposited Cu acts as a mediator for electron transfer between CdS and TiO2. The addition of citric acid as a hole "scavenger" allowed a further increase in activity, even in the case of TiO2.

Elemental doping can improve the photocatalytic activity of bulk graphitic carbon nitride (g-C3N4) under visible-light. In this study, sulfur and oxygen co-doped g-C3N4 (x% S-g-C3N4) was fabricated through thermal polymerization of macromolecular precursor obtained from hydrothermal pretreatment. The prepared photocatalysts, including g-C3N4, hydrothermally treated g-C3N4 (g-C3N4-HT), and x% S-g-C3N4, were analyzed under various conditions. Their ability to reduce Cr(VI) through photocatalytic reduction was evaluated comprehensively, taking into account the influence of catalyst dose, presence of inorganic anions, initial concentration and initial pH of Cr(VI) solution. The results showed that x% S-g-C3N4 (3% S-g-C3N4) possesses superior photocatalytic reduction activity to g-C3N4 and g-C3N4-HT, largely due to the co-doping. This co-doping strategy enhances the light harvesting capacity by modifying the electronic band structure of g-C3N4, and accelerates the excitons transfer and separation by optimizing its photoelectric properties. Additionally, the three-dimensional structure formed during preparation process enhances the stability and reusability of g-C3N4. [ABSTRACT FROM AUTHOR]

The synergistic removal of various pollutants is the challenge of environmental remediation due to mutual interference. The effect of Cr(VI) and tetracycline (TC) on photocatalytic reduction of U(VI) by MoS 2 /g-C 3 N 4 was investigated by batch and spectroscopic techniques. The high adsorption of U(VI) on MoS 2 /g-C 3 N 4 and the negative influence of photo-irradiation on U(VI) removal at pH 4.5 were observed. The batch experiments showed that the presence of TC and Cr(VI) improved the photoreduction of U(VI), whereas photocatalytic removal of Cr(VI) and TC were not influenced significantly. The adsorbed U(VI) was primarily photo-reduced into U(IV), while U(IV) was re-oxidized into U(VI) with further increasing irradiation by XPS analysis. According to quenching experiments, photo-degradation of TC was attributed to photogenerated holes, while the photo-reduction of Cr(VI) and U(VI) were due to •O 2 − and •OH radicals, respectively. These findings are crucial for the application of g-C 3 N 4 -bearing composites in the synergistic removal of radionuclide, heavy metal and organic at actual environmental cleanup. [ABSTRACT FROM AUTHOR]

The combination of zerovalent iron (Fe0) and titanium dioxide (TiO2) has been investigated as a promising method for environmental remediation. However, it is a challenge to prepare conveniently desirable Fe0/TiO2 nanocomposites with excellent efficiency and reusability. Here, a novel nanocomposite material, Fe0/TiO2@D201, was synthesized to enhance the removal of Cr(VI) from an aqueous system by impregnating Fe0 and TiO2 inside a commercial anion exchanger (D201). The proposed structure and Cr(VI) removal mechanism of Fe0/TiO2@D201 were confirmed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. Compared to the monometallic samples (Fe0-D201 and TiO2-D201), Fe0/TiO2@D201 showed outstanding Cr(VI) removal and the removal ratio reached up to 97.30% after 120 min of UV light irradiation. The removal of Cr(VI) by Fe0/TiO2@D201 remained high (91.70%) even after four cycles, indicating the stability of the nanocomposites toward Cr(VI) removal and their strong potential for practical applications. The addition of ethylenediaminetetraacetic acid (EDTA) positively affected the Cr(VI) reduction process, whereas the addition of Na2S2O8 negatively affected the Cr(VI) process. The XPS results revealed that the photocatalytic reduction of Cr(VI) by Fe0/TiO2@D201 involved the capture of photoexcited electrons and Fe0 reduction. A path for the photogenerated electrons engaging in the reduction reaction to improve the utilization of Fe0 was proposed. These results demonstrate that Fe0/TiO2@D201 is a promising alternative composite catalyst for the efficient Cr(VI) removal from contaminated water. [ABSTRACT FROM AUTHOR]

An easy wet chemical method was applied to effectively produce CuMn2O4@ZrO2 nanocomposite materials for photocatalytic applications. The obtained results designated that the prepared materials have good crystallinity with different element compositions, which confirms the potential incorporation between both CuMn2O4 and ZrO2 materials in one nanocomposite construction. As part of the current investigation, we analyzed both structural, optical, and semiconducting properties of the prepared nanocomposite materials. The CuMn2O4 included in the network of ZrO2 can influence both the optical characteristics and the physicochemical properties as well according to the UV–Vis spectroscopy and TEM investigations. The CuMn2O4@ZrO2 nanocomposites were applied for the visible-light-driven reduction of Cr(VI). For the 1.5 wt% CuMn2O4@ZrO2 nanocomposites, a complete Cr(VI) reduction into Cr(III) was obtained, indicating a significant improvement in its photocatalytic activity via the quantity of the minor addition of CuMn2O4. Even after five cycles of applications, the CuMn2O4@ZrO2 nanocomposites indicate superior photocatalytic proficiency of 95% in reducing Cr(VI) to Cr(III) ions while maintaining its remarkable durability. Consequently, the developed CuMn2O4@ZrO2 photocatalyst might be used as an environmentally material for the reduction of heavy metals. [ABSTRACT FROM AUTHOR]

The preparation of g-C3N4/mesoporous TiO2 composite catalyst by sol-gel blending method was studied and used in photocatalyctic reduction of Cr(VI). The photocatalyctic reduction performance and stability of g-C3 N4/mesoporous TiO2 were analyzed. The results show that the optimal doping ratio of g-C3N4, to mesoporous TiO2 is 1 : 5,and the specific surface area of g-C3N4/mesoporous TiO2 is 137.061 m²/g. The absorpion boundary redshfts to the vssible regon,and the band-gap width ss 2. 64 eV. The photocatalyic reducion rate of g-C3N4/mesoporous TiO2 is up to 100% under the conditions of mial Cr(VI) mass concentration of 1 mg/L,soluion pH = 5, catalyst dosage of 1. 6 g/L and no inorganic ions added for 45 min. under visible light irradiation, g-C3N4/mesoporous TiO2 can produce photogenerated electrons, which can reduce Cr(VI) adsorbed on the sufface of the catalyst to Cr (III). The reduction reaction is in line with the first-order reaction kinetics model. The photocatalytic reduction rate of the catalyst remains above 83% after 7 cycles, and it has potenial application value. [ABSTRACT FROM AUTHOR]

Water treatment through photocatalysts has become an important topic regarding environmental protection. In the present study, silver and TiO2 (Ag/TiO2) composites for photocatalysts were effectively synthesized by adopting the template induced method. The prepared samples were characterized using XRD, FTIR spectroscopy, SEM, and EDX. The constructed samples' particle size and shape were evaluated using a SEM, and the XRD patterns showed anatase crystalline phases. Their morphologies were controllable with changing concentration of reactants and calcination temperature. The synthesized composites act as catalyst in the degradation of methylene blue (MB) and reduction of Cr(VI) to Cr(III) under solar irradiation. In both of these activities, the best result has been shown by the 0.01 Ag/TiO2 composite. Methanol is used as the hole scavenger in the reduction of Cr(VI) to Cr(III). While the pH factor is important in the photocatalytic reduction of Cr(VI) to Cr(III). According to observations, S. macrospora and S. maydis were each subject to 0.01 Ag/TiO2 nanocomposites maximum antifungal activity, which was 38.4 mm and 34.3 mm, respectively. The outcomes demonstrate that both photocatalytic and antifungal properties are effectively displayed by the constructed material. [ABSTRACT FROM AUTHOR]

The recovery of Cr(VI) from the solution and the utilization of by-products are significant for wastewater treatment and environmental protection. In this study, the amorphous ZrO2 was prepared using a solvothermal method and used to treat the wastewater containing Cr(VI). Amorphous ZrO2 is effective for the photocatalytic reduction of Cr(VI). Without a sacrificial agent, 20 mL potassium dichromate solution (20 mg/L) is reduced to almost 0 mg/L within 10 min. Moreover, the by-products obtained from this process exhibit good performance in the catalytic dehydrogenation of ethane coupled with the reverse water–gas reaction. The maximum yield of ethylene is 12.9%, and the service life of the catalyst reached 160 min. Catalyst deactivation is caused by carbon deposition, and the deactivated catalyst is regenerated by roasting in the air. The feasibility of this green process is demonstrated, including the one-step photocatalytic reduction of Cr(VI) and utilization of the by-product as an ethane dehydrogenation catalyst. [ABSTRACT FROM AUTHOR]

An investigation on the reduction of Cr (VI) pollutant from tannery effluents using TiO2, SB/TiO2, and c-SB/TiO2 nano photocatalysts was presented in this study. For the preparation of Biochar-based TiO2 photocatalyst (SB/TiO2), tannery sludge was utilized as a precursor. Hydrothermal pre-treatment was adopted to prepare chemically activated SB/TiO2 and SB/TiO2 nanocomposites. The morphology, crystal structure, optical properties, and elemental composition of the prepared catalysts were analyzed by XRD, FT-IR, SEM–EDX, BET analysis, ZPC, PL, TGA, and Raman spectroscopy. The band gap analysis of Photocatalyst was measured using a DRS instrument, and band gap energy of 3.39 eV was obtained for c-SB/TiO2 photocatalyst. The developed c-SB/TiO2 catalyst exhibits a larger specific surface area of 646.85 m2/g than TiO2 and SB/TiO2 (74.58 m2/g and 573.74 m2/g), respectively. The enhanced photocatalytic activity for the pollutant removal was achieved by the photocatalyst due to their wide band gap and effective charge separation. The kinetic rate constant was achieved in the pseudo-first-order model, which fits well for the reduction of Cr (VI). Furthermore, at the optimal conditions of 10 mg/L contaminant concentration, pH 2, and 0.5 g/L catalyst dosage, 98.56% reduction was observed after 180 min of reaction. The OH acts as a major removal pathway for Cr (VI) contaminants with more than 50% reduction in COD. This study proves that c-SB/TiO2 photocatalysts can remove toxic contaminants under UV light irradiation with good recycling performance up to 5 times. [ABSTRACT FROM AUTHOR]

[Display omitted] It is an urgent and onerous task to develop catalysts for photocatalytic reduction of Cr(VI) in wastewater under wide pH range. In this work, a novel hierarchical Z-scheme MnO 2 /MnIn 2 S 4 (MISO) heterojunction photocatalyst with MnIn 2 S 4 nanosheets growing on the surface of β-MnO 2 nanorods is constructed for efficient photocatalytic reduction of Cr(VI). The optimized 2.0-MISO photocatalyst exhibits the almost 100% reduction efficiency in the pH range of 2.1–5.6 under visible light irradiation, and the apparent rate constant is 0.05814 min−1, which is 29.96 and 3.27 times higher than the pure β-MnO 2 and MnIn 2 S 4 , respectively. A efficient photocatalytic reduction of Cr(VI) to Cr(III) species on 2.0-MISO photocatalyst in actual industry wastewater (286.7 mg/L) up to 99.8% is achieved. Under natural light, the 2.0-MISO photocatalyst also shows rapid reduction of Cr(VI) species. The photocorrosion of MnIn 2 S 4 was significantly hindered by the construction of heterojunction. And the O 2 − and e− species are the main active species during the Cr(VI) photoreduction process. The connection mode between MnIn 2 S 4 and β-MnO 2 is verified by DFT calculations and a possible photocatalytic mechanism is also proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] The ecosystems and human health were seriously threatened by hexavalent chromium (Cr(VI)) in wastewater. In this article, using the idea of the highly matched energy band structure between indium sulfide (In 2 S 3) and MIL-53(Fe), a Type-II heterojunction has been constructed by loading In 2 S 3 on MIL-53(Fe) microrod to overcome the fault like high recombination rates of photogenerated electron-holes of In 2 S 3. The composite with 20:1 mass ratio of In 2 S 3 to MIL-53(Fe) (IM-2) was adopted as an optimal sample for efficient photocatalytic Cr(VI) reduction under visible light. Various characterization techniques were used to verify the characteristics of composites and delved into the structure-effect relationship between this heterojunction and its activity. Results showed that the reaction rate constants of the photoreduction process over IM-2 was ~ 4 and 26 times higher than those of pure In 2 S 3 and MIL-53(Fe), respectively, and the catalyst could maintain superior removal efficiency (88.6%) and steady crystal structure after four cycles. First-principles calculations further illustrated that the heterostructure formed between In 2 S 3 and MIL-53(Fe) could effectively accelerate the separation of photogenerated electrons and holes, thus improving the photocatalytic reduction performance. Moreover, the active species analyses revealed that the superoxide radicals and electrons were mainly involved in the reduction of Cr(VI). [ABSTRACT FROM AUTHOR]

In this research, the dimensional catalysts of pure g-C 3 N 4 photocatalysts (1D, 2D, and 3D) were investigated for the reduction of the highly toxic/carcinogenic Cr(VI) under visible light irradiation. The catalysts underwent explanation through various surface analysis techniques. According to the BET data, the specific surface area of the 3D catalyst was 1.3 and 7 times higher than those of the 2D and 1D CN catalysts, respectively. The 3D catalyst demonstrated superior performance, achieving an efficiency greater than 99% within 60 min under visible light irradiation in the presence of EDTA due to the abundance of active sites. The study also delved into the influence of factors such as the amount of EDTA-hole scavenger, pH, catalyst dosage, and temperature on the photocatalytic reduction of Cr(VI). Moreover, the 3D catalyst showed excellent reusability, maintaining an efficiency of more than 80% even after 10 cycles, and performed effectively in real water samples. The 3D CN catalyst, with its facile synthesis process, excellent visible light harvesting properties, high reduction efficiency that sustains over multiple cycles, and outstanding performance in real water samples, presents a significant advancement for practical applications in environmental remediation. This research contributes to a new understanding of developing efficient degradation methods for heavy metals in polluted water, highlighting the potential of 3D g-C3N4 catalysts in environmental cleanup efforts. [Display omitted] • Dimensional g-C 3 N 4 photocatalysts was synthesized for Cr(VI) reduction. • 3D catalyst showed 1.3 to 7 times greater surface area than 1D/2D counterparts. • 3D catalyst enhanced Cr(VI) reduction through more efficient electron transfer. • 3D catalyst showed superior reusability and effectiveness in real water samples. [ABSTRACT FROM AUTHOR]

UV-light irradiated photocatalytic reduction of Cr(VI) to Cr(III) in aqueous solution using ZnFe2O4 nanoparticles in the presence of formic acid was reported. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and UV–Vis diffuse reflectance spectroscopy (DRS) were employed to characterize ZnFe2O4 nanoparticles. The photocatalytic activity of pure ZnFe2O4 under UV irradiation was significantly low. However, the Cr(VI) reduction efficiency on nano-sized ZnFe2O4 in the presence of 0.40% formic acid reached 95.4% within 4 h. Herein, the effect of pH, photocatalyst amount, initial concentration of Cr(VI) and formic acid concentration on the photocatalytic reduction of Cr(VI) was investigated. The results indicated that the photocatalytic reduction of Cr(VI) decreased with increase in the initial concentration of Cr(VI), photocatalyst dosage and pH. The reduction rate constant declined from 0.017 min−1 to 0.0023 min−1 with the increase in initial concentration of Cr(VI) from 5 to 25 mg L−1. However, the reduction rate constant sharply increased from 0.000075 min−1 to 0.0127 min−1 with the increase in formic acid concentration from 0.05% to 0.40%. The formic acid could capture the photogenerated holes, and eventually formate (HCOO–) ions could be converted into carbon dioxide radicals (•CO2−). Because of more negative redox potential for •CO2− radicals, Cr(VI) species could easily be reduced to Cr(III) under UV irradiation. The pseudo-first-order kinetic reaction was confirmed for this reduction process. A tenable mechanism for the photocatalytic Cr(VI) reduction has also been demonstrated. [ABSTRACT FROM AUTHOR]

Hexavalent chromium, Cr(VI), is a toxic, mutagenic and carcinogenic species. We report here the semiconductor-based, photocatalytic reduction of Cr(VI) to trivalent chromium, Cr(III), using CdS nanorods (NRs) as the photocatalyst under visible light illumination. The CdS NRs were synthesized by a facile and scalable solvothermal method in which ethylenediamine acts as solvent and morphology controller. The CdS NRs produced were studied by PXRD, Raman, FESEM, EDX, XPS, PL, UV-visible DRS and BET techniques in order to investigate their structural, morphological and optical properties, as well as their porosity. The photoreduction of Cr(VI) to Cr(III) under visible light illumination was performed under a variety of conditions, i.e., varying the irradiation time, pH, substrate concentration, and the amount of photocatalyst. The maximum photoreduction of Cr(VI) to Cr(III) (99%) was achieved using 60 min of irradiation under acidic conditions (pH 4). The excellent photoreduction ability of the CdS NRs can be attributed to their rod-like structure together with their small particle size, large surface area, and clean surfaces. These properties enhanced separation of the photo-generated electron-hole pairs, which was confirmed by the XRD, BET, and PL measurements. In addition, the results of a kinetic study indicated that the photoreduction of Cr(VI) to Cr(III) follows a pseudo-first-order kinetic model. A possible mechanism for the photocatalytic reduction of Cr(VI) to Cr(III) is also proposed in this paper. [ABSTRACT FROM AUTHOR]

In the current research, a visible light photocatalytic method, in which the CuO/Kaolin nanocomposite photocatalyst was utilized to reduce Cr(VI), was investigated. Response surface methodology was applied to determine the influence of various variables (individual effect and correlated effects) and the optimum conditions for Cr(VI) reduction. Analysis of variance (ANOVA) indicated a high coefficient of determination value (R2 = 0.9812) for the developed second-order regression model, suggesting the suitability of the model. Approximately 99.99, 95.77 and 79.6% of Cr(VI) in a synthetic water, drinking water and electroplating wastewater samples were reduced, respectively. [ABSTRACT FROM AUTHOR]

Photocatalytic reduction of heavy metal ions is a green and promising technology which requires electrons with enough negative energy levels as well as efficient separation property from photo-generated holes of photocatalysts. For WO3, the low conduction band edge and the severe photo-generated charge carrier recombination limited its application in photocatalytic reduction of pollutants. In this work, we prepared WO3@PVP with PVP capped WO3 by a simple one-step hydrothermal method, which showed an elevated energy band structure and improved charge carrier separation property. XRD, SEM, TEM, XPS, DRS, and the photocurrent density test were carried out to study the properties of the composite. Results demonstrated monoclinic WO3 with a size of ∼100–250 nm capped by PVP was obtained, which possessed fewer lattice defects inside but more defects (W5+) on the surface. Moreover, the results of the photocatalytic experiment showed the kinetic constant of Cr(VI) reduction process on WO3@PVP was 0.532 h−1, which was 3.1 times higher than that on WO3 (0.174 h−1), demonstrating WO3@PVP with good photocatalytic capability for Cr(VI) reduction. This can be attributed to the improved charge carrier separation performance, the improved adsorption capacity and the elevated conduction band edge of WO3@PVP. More importantly, the energy band structure of WO3@PVP was proved elevated with a value as high as 1.14 eV than that of WO3 nanoparticles, which enables WO3@PVP a promising material in the photocatalytic reduction reaction of heavy metal ions from wastewater.

In recent years, photocatalytic reduction of Cr(VI) to Cr(III) by TiO2 nanostructures, as a potent environmental technology has attracted a lot of attention. However, several defects including the large band gap energy of TiO2, fast photogenerated charge recombination and re-oxidation of Cr(III) restrict their practical application. In this work, the incorporation of TiO2 nanotubes (TNTs) with magnetic activated carbon (MAC) and photoreduction in the presence of a hole scavenger were studied as a preferable approach. The results revealed that coupling TNTs with 2 wt% MAC can boost the surface area from 89.54 to 307.87 m2 g−1 as well as decrease the band gap energy from 3.1 to 2.7 eV. As a consequence of the enhancement in textural features and optical properties, TNTs/MAC (2%) led to improvement of photoreduction efficiency (from 47% to 66%) in comparison with the TNTs. Meanwhile, the experiments demonstrated that using 0.2 g TNTs/MAC as an optimal dosage in acidic solution increases the photoreduction efficiency up to 81%. The hole scavenger investigation had a marvellous result. It was found that in the presence of oxalic acid, TNTs/MAC (2%) could reduce 97% of Cr(VI) which it was due to trapping oxidative species and charge-transfer-complex-mediated process. Furthermore, the kinetic study affirmed that the photoreduction follow first-order kinetics and the reaction rate constants by TNTs/MAC (2%) are 1.5 times as great as those of TNTs. Moreover, the reusability tests illustrated TNTs/MAC (2%) has good stability and is active even up to the six runs. [ABSTRACT FROM AUTHOR]

An effective cellulose/MoS2 (Ce/MoS2) composite was synthesized via a one-pot microwave-assisted ionic liquid method for the photocatalytic reduction of toxic Cr(VI). Effects of ionic liquids (ILs) on the MoS2 nanostructure were considered, and the obtained composite was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometry (XPS), and electrochemical impedance spectroscopy (EIS). The results indicated that the MoS2 nanoplates were anchored and dispersed on the surface of the cellulose. Compared with the pristine MoS2, the support of the cellulose greatly enhanced the photocatalytic reduction efficiency of Cr(VI) ions in solution, from 65.9% to nearly 100%. The reduction mechanism was considered, and the results implied that the simultaneous reduction of Cr(VI) during the initial dark adsorption process was observed due to the effect of citric acid as a hole scavenger. Finally, regeneration tests revealed that the Ce/MoS2 composite could be recycled and reused. [ABSTRACT FROM AUTHOR]

Abstract Antibiotics and heavy metals often coexist in polluted environment, and the harm of combined pollution is greater than that of single pollution. In this study, a series of graphene supported p-n heterojunction rGO@Cu 2 O/BiVO 4 composites are synthesized with different Cu 2 O doping for simultaneous detoxification of Cr(VI) and antibiotics. The obtained photocatalysts (rGO@Cu 2 O/BiVO 4) with proper loading amount of Cu 2 O shows the a high photocatalytic degradation activity for simultaneously efficient Cr(VI) reduction and sulfamethoxazole (SMZ) oxidation under LED light at neutral pH. The Cr(VI) was completely transformed to Cr(III) rather than simply Cr(VI) adsorbed on the surface of rGO@Cu 2 O/BiVO 4. The photocatalytic activity of composites can be attributed to excellent electrical conductivity of rGO and the p-n heterojunction between Cu 2 O and BiVO 4 , which promotes the spatial separation of photogenerated charges at the heterojunction boundary and inhibits of the photogenerated h + and e − recombination. It's confirmed that h +, O 2 − and OH are the main reactive species for the photocatalytic SMZ oxidation, and the most important reactive species is h +. Finally, the tentative degradation pathways of SMZ are proposed based on the liquid chromatography-triple quadrupole mass spectrometry analysis. This work provides an effective approach for the treatment of water that contains SMZ and Cr(VI) under LED light. Graphical abstract Image 1 Highlights • rGO@Cu 2 O/BiVO 4 p-n heterojunction photocatalysts were successfully prepared. • Simultaneous and efficient Cr(VI) reduction and SMZ oxidation. • The joint photocatalysis enhances the degradation activity of Cr(VI) and SMZ. • O 2 − and OH are major reactive species. • The degradation pathways of SMZ are proposed based on the LC-MS-MS analysis. [ABSTRACT FROM AUTHOR]

Exploiting excellent photocatalytic activity and stable heterostructure composites are of critical importance for environmental sustainability. The spherical Bi2WO6/Bi2S3/MoS2 n-p heterojunction is first prepared via an in situ hydrothermal method using Bi2WO6, Na2MoO4·2H2O, and CH4N2S, in which the intermediate phase Bi2S3 is formed due to chemical coupling interaction of Bi2WO6 and CH4N2S. Scanning electron microscopy indicates that the compactness of the sample can be easily adjusted by changing the contents of S and Mo sources in the solution. The results of ultraviolet–visible (UV–vis) diffuse reflectance spectra, photoluminescence, transient photocurrent response, and electrochemical impedance spectra indicate that the formation of heterojunctions contributes to enhancing visible-light utilization and promoting photogenerated carrier separation and transfer. The composite material is used as a catalyst for the visible light photocatalytic reduction of Cr(VI). Remarkably, the optimal Bi2WO6/Bi2S3/MoS2 n-p heterojunction achieves the greatest Cr(VI) reduction rate of 100% within 75 min (λ > 420 nm, pH = 2); this rate is considerably better than the Cr(VI) reduction rate of pure Bi2WO6. The recycling experiment also reveals that the photocatalytic performance of the n-p heterojunction toward Cr(VI) is still maintained at 80% after three cycles, indicating that the n-p heterojunction has excellent structural stability. The capture experiment proves that the main active species in the system are electrons. The reasonable mechanism of Bi2WO6/Bi2S3/MoS2 photocatalytic reduction Cr(VI) is proposed. Our work provides new research ideas for the design of ternary heterojunction composites and new strategies for the development of photocatalysts for wastewater treatment.

In the present study, we report a simple approach for the fabrication of novel sulphur decorated MoO 3 nanorods (S@MoO 3 nanorods) by using simple solution process method for the very first time. The phase structural, morphology and optical properties of the as-prepared nanomaterials were comparatively characterized. The sulphur (S) nanosheets were well decorated on the surface of MoO 3 rods which was clearly observed from TEM images. The applicability of the as synthesized S@MoO 3 nanocomposite was demonstrated as superior photocatalyst for the photocatalytic reduction of toxic hexavalent chromium Cr(VI) to nontoxic trivalent chromium Cr(III) under visible light illumination. The photocatalytic reduction results suggested that the 1% of S@MoO 3 nanorods was exhibited excellent visible light photocatalytic activity efficiency compared to pure MoO 3 , S and other S@MoO 3 nanocomposites. The enhancement in the photocatalytic performance of 1% S@MoO 3 nanorods was mainly attributed to the strong absorption in visible region and low recombination or high separation efficiency for photogenerated electrons and holes. The trapping experiments reveals that O 2 ¯ radical species was strongly supported for the photocatalytic reduction of Cr(VI). The present protocols reported open up an S decorated photocatalyst might be a potential candidate for Cr(VI) removal in environmental. [ABSTRACT FROM AUTHOR]

As a typical visible-light-responsive photocatalyst, the photoreactivity of BiVO 4 is not high enough for practical application due to its limited visible light harvesting ability and quick recombination rate of photo-generated electron-hole pairs. In the present study, surface modification of BiVO 4 with Bi 2 S 3 , forming walnut-like core-shell structured BiVO 4 @Bi 2 S 3 , was achieved by a simple ion-exchange reaction between Na 2 S and BiVO 4 . The photoreactivity of the photocatalyst was evaluated by photoreduction of Cr(VI) in solution under visible light irradiation (λ ≥ 420 nm). The effect of weight ratio of Na 2 S·9H 2 O to BiVO 4 on the structure and photocatalytic performance of BiVO 4 @ Bi 2 S 3 hybridized photocatalyst was systematically studied. It was found that a layer of Bi 2 S 3 was successfully covered on the surface of walnut-like BiVO 4 microspheres after introduction of Na 2 S. The formed Bi 2 S 3 shell not only widely extends the visible-light-responsive range, but also sharply retards the recombination of photo-generated electrons and holes of BiVO 4 photocatalyst. With increase in the weight ratio of Na 2 S·9H 2 O to BiVO 4 , the photoreactivity of BiVO 4 increases first and then decreases with an optimal wight ratio of 3.0 (S3 sample). The photocatalytic activity of S3 sample (BiVO 4 @Bi 2 S 3 ) increases 57.2 times when compared with that of pristine BiVO 4 sample after irradiation for 40 min. The enhanced photocatalytic activity of walnut-like BiVO 4 @Bi 2 S 3 microsphere was attributed to the synergistic effect of enhanced visible light harvesting ability due to the sensitization of Bi 2 S 3 and retarded recombination of carriers because of the formation of heterojunction between two semiconductors of BiVO 4 and Bi 2 S 3 . [ABSTRACT FROM AUTHOR]

[Display omitted] • TiO 2 nanoparticles were successfully synthesized by novel sonoelectrochemical method. • The as-prepared nanomaterial possessed both anatase-phase and superior surface area. • The generated O atoms directly attach to Ti on the electrode surface to form TiO 2. • These materials exhibited an excellent photocatalytic removal efficiency of Cr(VI). This work proposed a highly efficient sonoelectrochemical technique for the straightforward synthesis of TiO 2 nanoparticles (NPs) at a mild temperature of 60 °C under an atmosphere environment. The NPs were then applied for photocatalytic removal of Cr(VI) in an aqueous solution. The NPs possess an anatase crystalline phase with a particle size of about 6.5 nm and a superior surface area of 202.85 m2/g and exhibit good photocatalytic reduction of Cr(VI) under UVA irradiation. [ABSTRACT FROM AUTHOR]

This paper describes the photocatalytic reduction of aqueous hexavalent chromium (Cr(VI)), a potential human carcinogen and genotoxin, by copper doped TiO 2 (Cu-TiO 2 ) prepared by the simple-evaporation and calcination of CuCl 2 and TiO 2 , under UV-A irradiation in the absence of hole scavengers. The Cu-TiO 2 prepared at a Cu to TiO 2 mass ratio of 1.5:100 and a calcination temperature of 300 °C showed the fastest photocatalytic reduction of Cr(VI). The reduction by the Cu-TiO 2 followed pseudo-first order reaction kinetics, and its rate was twice as fast as that of unmodified TiO 2 at pH 3. The Cu-TiO 2 reached its maximum Cr(VI) reduction rate at pH 5, producing steady state hydrated electron concentrations ([ e − ] ss ) 3.3 times higher than those by unmodified TiO 2 . The optimum working pH of the Cu-TiO 2 is higher than that of many other photocatalysts. The XPS, XRD, TEM and SEM spectra all confirmed the incorporation of Cu into TiO 2 , and the BET analysis showed the similar surface areas of the Cu-TiO 2 and unmodified TiO 2 . The enhanced reduction rate by the Cu-TiO 2 was thus attributed to the reduced electron-hole recombination rate. More importantly, the Cr(VI) reduction rate by the Cu-TiO 2 was only reduced by 20% with increasing alkalinity from 0 to 200 mg/L at pH 7, and it was not affected by the presence of NOM at concentrations up to 1 ppm. Lastly, the Cr(VI) reduction rate by the Cu-TiO 2 was faster in tap water than in double deionized water. The wider working pH (optimum at pH 5), without addition of hole scavengers, and the faster reduction in tap water suggest the superior performance of the Cu-TiO 2 photocatalyst in real water matrices. [ABSTRACT FROM AUTHOR]

Efficient separation and transfer of photogenerated electron/hole as well as enhanced visible light absorption play essential roles in photocatalytic reactions. To promote the photocatalytic reduction of Cr(VI), a toxic heavy metal ion, multiwalled carbon nanotube (MWCNT) was introduced as an electron acceptor into NH-MIL-68(In). This led to the growth of a willow leaf-like metal-organic framework (MOF) on an MWCNT backbone forming MWCNT/NH-MIL-68(In) (PL-1), which showed a highly efficient transfer of photogenerated carriers. Moreover, MWCNT incorporation introduced more mesopores for Cr(VI) diffusion and enhanced the visible light adsorption without lowering the conduction band position. As a result, the photocatalytic kinetic constant of PL-1 was found to be almost three times higher than that of the parent NH-MIL-68(In). Thus, growing MOFs on MWCNTs provides a facile and promising solution for effective remediation of environmental pollution by utilizing solar energy. This work provides the first example of using MWCNT/MOF composites for photocatalytic reactions. [ABSTRACT FROM AUTHOR]

As chromium is a common heavy metal contaminant in water, we have prepared N-F-Al tri-doped TiO catalyst for Cr(VI) removal under visible light. The sample was prepared via a sol-gel method and was characterized by XRD, BET, UV-vis DRS, XPS and SEM techniques. In the photocatalytic experiments, effects of Al/Ti ratio, F/Ti ratio, calcination temperature and different dopants were investigated. The optimum Al/Ti molar ratio, F/Ti ratio and calcination temperature proved to be 0.01, 0.1 and 500 °C, respectively, which is in accordance with the characterization analysis. Catalysts prepared under this condition showed a high photoactivity for Cr(VI) removal in water. [ABSTRACT FROM AUTHOR]

To further enhance the photoactivity of virgin TiO2, we prepared N-doped TiO2 (N-TiO2) by sol-gel method and used it to remove Cr(VI) ions from water under visible light. The catalysts were characterized by TEM, XRD, BET and UV-vis techniques. Better crystalline structure, larger specific surface area and decreased band-gap width were obtained after the insertion of N atoms into TiO lattice. Several influencing factors were also investigated. The removal efficiency of Cr(VI) increases with the decrease of initial Cr(VI) concentration or the increase of catalyst dosage. Addition of glucose or some inorganic ions (Mg, Al) can promote the photoreduction process by improving the quantum efficiency. The kinetics and mechanism were discussed as well. [ABSTRACT FROM AUTHOR]

This study prepared N-F co-doped TiO2-pillared clay nanocomposites by the sol-gel method and evaluated the effects of initial Cr(VI) concentration, pillaring, doping and light irradiation on Cr(VI) removal in aqueous solution. The samples were characterized using XRD, BET, UV-vis and SEM. Pillaring improved the adsorption ability and settling ability of TiO2 but reduced the photocatalytic reduction ability. N-F co-doping created an increase on both adsorption ability and photocatalytic reduction ability. The working life of TiO2 was prolonged greatly both by pillaring and N-F co-doping. Further, stronger light power or lower initial Cr(VI) concentration increased the removal efficiency of Cr(VI). [ABSTRACT FROM AUTHOR]

Flower-like ZnO hollow microspheres were synthesized on flexible ceramic mesh substrate using a simple and economical hydrothermal technique and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic reduction of Cr(VI) in leather tannery wastewater by flower-like ZnO hollow microspheres was evaluated under ultraviolet light irradiation for the first time. The addition of different organics and pH value of the reaction solution played important roles in the photocatalytic reduction of Cr(VI). In addition, UV radiation intensity and catalyst content were critical parameters in the photocatalytic reduction process and their effects were also investigated. Under the optimal conditions, ZnO hollow microspheres exhibited excellent removal efficiency of Cr(VI) (~86%) and good photocatalytic stability. Moreover, more than 24% biochemical oxygen demand (BOD 5 ), 32% chemical oxygen demand (COD) and 30% total organic carbon (TOC) of tannery wastewater were reduced significantly after only 180 min of exposure to the UV lamp. It shows much promise to be an attractive photocatalyst for photocatalytic application. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) was modified onto 3D flower-like molybdenum disulfide (MoS 2 ) to prepare a novel organic–inorganic hybrid material, PANI@MoS 2 . PANI@MoS 2 was characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The results indicate that PANI was modified onto MoS 2 . PANI@MoS 2 was applied as an adsorbent to remove Cr(VI) from aqueous solutions, and the adsorption isotherms fit well to the Langmuir model; the maximum removal capacity of Cr(VI) by PANI@MoS 2 was 526.3 and 623.2 mg/g at pH 3.0 and 1.5, respectively. PANI@MoS 2 exhibited an enhanced removal capacity of Cr(VI) in comparison with bare MoS 2 and other adsorbents. The adsorption of Cr(VI) on PANI@MoS 2 might be attributed to the complexation between the amine and imine groups on the surface of PANI@MoS 2 with Cr(VI). This study implies that the hybrid material PANI@MoS 2 is a potential adsorbent for Cr(VI) removal from large volumes of aqueous solutions. [ABSTRACT FROM AUTHOR]

Highly ordered TiO2nanotube arrays (NTs) have been widely used for photocatalysis application. In this study, to further improve the photocatalysis activity of TiO2NTs, Cu/TiO2NTs were prepared through an anodic oxidation and impregnation–reduction method. The morphology and crystalline phase of the pure TiO2NTs and Cu/TiO2NTs were characterized by SEM and X-ray diffraction. The photocatalytic performance of Cu/TiO2NTs was evaluated by photocatalytic reduction of Cr(VI) under UV light. The rate constant of photocatalytic reduction of Cr(VI) on Cu0.01/TiO2NTs which had the optimal Cu loading content was 9.5 times higher than that on unmodified TiO2NTs. And the experiment results of different initial concentration of Cr(VI) and pH demonstrated that they greatly influenced the removal efficiency of Cr(VI). The photoelectric properties of TiO2NTs with Cu particle loading were investigated by photoelectrochemical characterization, including photocurrent response, open-circuit voltage, electro-chemical impedance spectroscopy Nynquist plots, and Mott–Schottky plots. The enhancement of the photocatalytic performance of Cu/TiO2NTs indicated that the electrons could transfer faster and be utilized more easily due to the formation of Schottky barrier on the interface of Cu and TiO2. The detailed electrons transfer mechanism of Cu/TiO2NTs was proposed. [ABSTRACT FROM PUBLISHER]

A new Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) sandwich nanosphere with Ag nanoparticles as an interim layer is fabricated, and they shows excellent photocatalytic Cr(VI) reduction performance and stability in cyclic use and harsh environment. [Display omitted] • A novel Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) sandwich nanosphere with Ag nanoparticles as an interim layer is developed. • Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) shows excellent photocatalytic Cr(VI) reduction performance. • Outmost mesoporous TiO 2 -ZrO 2 shell enhances the stability of Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) in cyclic use and harsh environment. • Mechanisms for Cr(VI) reduction are proposed. A sandwich structured Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) magnetic nanosphere with Ag nanoparticles as an interim layer was fabricated with in situ deposition of Ag nanoparticles onto Fe 3 O 4 nanospheres and subsequent coating an outmost shell of mesoporous TiO 2 -ZrO 2. As compared to Fe 3 O 4 /m(TiO 2 -ZrO 2)/Ag with Ag nanoparticles as the outmost layer, unique Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) sandwich nanospheres possess higher efficient charge migration and larger specific surface area disclosed by the BET and photoelectrochemical characterizations, so they present improved photocatalytic activity toward Cr(VI) reduction. In addition, they have high thermal stability because mesoporous TiO 2 -ZrO 2 outmost shell could protect the interim Ag nanoparticles from damage and agglomeration at high temperature. Results showed reduction efficiency of Cr(VI) of Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) reached 98.4 % in 30 min, as 1.6 times as that of Fe 3 O 4 /m(TiO 2 -ZrO 2)/Ag. The Fe 3 O 4 /Ag/m(TiO 2 -ZrO 2) still obtained 91.3 % and 87.9 % reduction ratio after calcination at 500 ℃ and recycling 5 times, respectively. The photocatalytic mechanism was also revealed by scavenger experiments and ERP analysis. This work provided a good example for further design and preparation of magnetic photocatalysts with high performance for the remediation of heavy metal pollutants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized Ag decorated magnetic core–shell Fe 3 O 4 @MoS 2 composite via hydrothermal. • Better photogenerated electron transfer effect and photocatalytic performance driven by Ag0 doping. • Magnetic core–shell structure brought about excellent solid–liquid separability. • Great enhancement of Cr (VI) reduction efficiency under the sunlight. An Ag decorated magnetic core–shell Fe 3 O 4 @MoS 2 composite was synthesized in this work to improve the photocatalytic performance and solid–liquid separation of MoS 2 based materials. The composite was evaluated by UV–vis IS-NIR spectrometer, photoluminescence (PL) spectra, XRD, XPS, EDS, EIS and was devoted to reduce the toxicity of wastewater which contains hexavalent chromium(Cr(VI)) for its potential economic value. The results have shown that the core–shell structure effectively inhibits the stack of nanosheets, increases the specific surface area of the material, and exposes more active sites. Besides, loading Ag can effectively promote the migration of photogenerated electrons and improve the photocatalytic performance. On this basis, the better separability and retrievability which got form the magnetic core–shell Fe 3 O 4 may immensely promote the photodegradation technique of hexavalent chromium (Cr (VI)) and provided a new strategy for photocatalytic degradation of industrial industrial wastewater that containing hexavalent chromium (Cr (VI)). [ABSTRACT FROM AUTHOR]

α-Fe 2 O 3 /g-C 3 N 4 composites were fabricated by a facile hydrothermal method. The prepared composites were characterized by XRD, XPS, TEM, DRS, PL and photoelectrochemical measurement. Under visible light irradiation, α-Fe 2 O 3 /g-C 3 N 4 composite displays higher photocatalytic activity than pure g-C 3 N 4 and α-Fe 2 O 3 for Cr(VI) reduction. The enhanced photocatalytic activity should be attributed to the well-matched band structure and intimate contact interfaces between g-C 3 N 4 and α-Fe 2 O 3 , which lead to the effective transfer and separation of the photogenerated charge carriers. The decoration of α-Fe 2 O 3 does not affect the morphology and size of g-C 3 N 4 . The lower photoluminescence intensity and higher photocurrent density indicate the effective transfer and separation of photogenerated charge carriers. α-Fe 2 O 3 /g-C 3 N 4 composite shows more intense optical absorption compared with pure g-C 3 N 4 . The addition of hole scavengers can greatly facilitate the photocatalytic reduction of Cr(VI) and the α-Fe 2 O 3 /g-C 3 N 4 composite shows excellent stability during the photocatalytic reduction of Cr(VI). [ABSTRACT FROM AUTHOR]

In this study, the nanoparticles of TiO2-P25 in the slurry situation were used for photoreduction of Cr(VI). The experiments were conducted in different operational conditions such as initial concentration of Cr(VI), varying dosages of photocatalyst, and different irradiation times and pHs. Using the response surface methodology, the mathematical equation for estimating the percentage of Cr(VI) photocatalytic removal was obtained. For the first time, the results from this model were utilized for modeling the process by artificial neural networks (ANN). The comparison of the analyzed data obtained from ANN and the experimental data showed that the method was highly efficient in the modeling of process. The relative importance of the parameters affecting the process evaluated by the weights from ANN indicated that pH was the most important factor in photocatalytic reduction of Cr(VI). [ABSTRACT FROM AUTHOR]

TiO 2 coated on activated carbon (TiO 2 /AC) was synthesized by a facile sol-hydrothermal preparation. The as-prepared TiO 2 /AC was modified by sequential treatment of nitric acid and thionyl chloride, followed by surface attaching of diethylenetriamine. The obtained materials were characterized by transmission electron microscopy, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, BET adsorption, and their adsorption–photocatalytic reduction activities were evaluated by the removal of aqueous Cr(VI). The results showed that TiO 2 particles were homogeneously deposited on the surface of activated carbon, and diethylenetriamine was grafted covalently onto the surface of TiO 2 /AC through amide linkage. The diethylenetriamine-functionalized TiO 2 /AC (TiO 2 /AC-DETA) exhibits high adsorption capability for Cr(VI) through electrostatic, coordinative and hydrogen bonding interactions. The significant enhancement of photocatalytic activity of TiO 2 /AC-DETA for reduction of Cr(VI) was observed, which was mainly attributed to the enrichment of Cr(VI) onto the surface of AC and successive fast interfacial transfer of Cr(VI) and photogenerated electrons resulted from the intimate contact between AC and TiO 2 through dense heterojunctions by forming of C–O–Ti linkages. [ABSTRACT FROM AUTHOR]

Porous metal-organic frameworks (MOFs) have been arousing a great interest in exploring the application of MOFs as photocatalyst in environment remediation. In this work, two different MOFs, Ti-benzenedicarboxylate (MIL-125(Ti)) and amino-functionalized Ti-benzenedicarboxylate (NH 2 -MIL-125(Ti)) were successfully synthesized via a facile solvothermal method. The MIL-125(Ti) and NH 2 -MIL-125(Ti) were well characterized by XRD, SEM, XPS, N 2 adsorption–desorption measurements, thermogravimetric analysis and UV–vis diffuse reflectance spectra (DRS). It is revealed that the NH 2 -MIL-125(Ti) has well crystalline lattice, large surface area and mesoporous structure, chemical and thermal stability, and enhanced visible-light absorption up to 520 nm, which was associated with the chromophore (amino group) in the organic linker. Compared with MIL-125(Ti), NH 2 -MIL-125(Ti) exhibited more efficient photocatalytic activity for Cr(VI) reduction from aqueous solution under visible-light irradiation. The addition of hole scavenger, the hole scavenger concentration and the pH value of the reaction solution played important roles in the photo-catalytic reduction of Cr(VI). The presence of Ti 3+ –Ti 4+ intervalence electron transfer was the main reason for photo-excited electrons transportation from titanium-oxo clusters to Cr(VI), facilitating the Cr(VI) reduction under the acid condition. It was demonstrated that amino-functionalized Ti(IV)-based MOFs could be promising visible-light photocatalysts for the treatment of Cr(VI)-contained wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photocatalyst of CaTiO 3 was synthesized by a one-pot facile solvothermal method. • CaTiO 3 exhibited efficient photocatalytic reduction performance of Cr(VI) at low pH. • The surface reduced Cr(III) species could be conducive to the removal of Cr(VI). Pollution of the environment with hexavalent chromium (Cr(VI)) has attracted a lot of concern recently as the high toxicity and mobility of Cr(VI). Hence, the removal of Cr(VI) from aquatic systems has become an urgent issue. In this study, we synthesized an efficient photocatalyst of cubic CaTiO 3 particles via a facile solvothermal method, and investigated it removal performance towards Cr(VI). Under low pH condition, we found that the photogenerated electrons played a significant role in photocatalytic reduction of Cr(VI) verified through trapping experiment. Moreover, the more positive zeta potential of CaTiO 3 after the completion of photocatalytic experiment was due to the existing trivalent chromium (Cr(III)) species. It could benefit the electrostatic attraction between anionic Cr(VI) species and the surface of CaTiO 3. Meanwhile, the X-ray photoelectron spectroscopy (XPS) revealed that the Cr 2p peak of the photocatalytic treated sample was more apparent than that of the adsorption treated sample, indicating that large numbers of Cr species were loaded on CaTiO 3 surface after the photocatalytic treatment. Herein, the surface reduced Cr(III) species on CaTiO 3 played a positive role in the loading of Cr(VI) on CaTiO 3 surface under low pH. [ABSTRACT FROM AUTHOR]

The Nb5+-doping strategy was adopted to enhance the photocatalytic efficiency of SrTiO 3 to overcome the limitation for its practical photocatalytic applications. Different amounts of Nb5+ doped SrTiO 3 (Nb-SrTiO 3) mesoporous nanospheres were synthesized via a convenient hydrothermal approach. The photocatalytic reduction of aqueous Cr(VI) using the Nb-SrTiO 3 products under xenon lamp irradiation was investigated. Results indicated that 3% Nb-SrTiO 3 was the optimum product, which exhibited a photocatalytic efficiency 3 times as much as that of SrTiO 3 and a fair reuse stability. Moreover, 3% Nb-SrTiO 3 also demonstrated higher photocatalytic efficiency than many other metal cations doped SrTiO 3 synthesized via the same process and a number of previously reported photocatalysts. The best photocatalytic activity of 3% Nb-SrTiO 3 was found to be predominantly due to its most efficient separation and transfer of photogenerated holes and electrons. This study suggests that Nb-SrTiO 3 is a potential efficient photocatalyst for the remediation of Cr(VI)-contaminated water. [Display omitted] • Nb5+-doped SrTiO 3 mesoporous nanospheres were synthesized by a hydrothermal method. • 3% Nb-SrTiO 3 has far higher photocatalytic activity than SrTiO 3 in Cr(VI) reduction. • It outperforms many other metal ions doped SrTiO 3 and many reported photocatalysts. • It has good photocatalytic stability. • Its higher activity mainly results from enhanced separation and transfer of e − and h + . [ABSTRACT FROM AUTHOR]