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In the current study, copper oxide (CuO) and manganese oxide (MnO) nanoparticles (NPs) were synthesized through a simple, cost-efficient, and green method using watermelon seed shell extract as a stabilizing and reducing agent. The synthesized CuO and MnO NPs were characterized by using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Ultraviolet spectroscopy (UV). The particle sizes of CuO and MnO NPs were determined to be in the range of 15–97 and 6–51 nm, respectively, by TEM and XRD analysis. The photocatalytic performance of the CuO and MnO NPs used as catalysts were investigated for the photocatalytic reduction of methylene blue in an aqueous solution. In the photocatalytic reduction of methylene blue, sodium borohydride (NaBH4) was used as the reducing agent. The CuO and MnO NPs were capable to remove 96.58% (in 70 min) and 96.60% (in 140 min) of methylene blue from aqueous media, respectively. Besides, the kinetics of the photocatalytic reaction was investigated by a pseudo-first order model, and the reaction rate coefficient for methylene blue with CuO and MnO NPs were calculated as 0.0426 and 0.0235 min−1, respectively. The results demonstrated that the synthesized CuO and MnO NPs through the green method were promising catalysts to improve the photocatalytic reduction performance of methylene blue. The copper oxide (CuO) and manganese oxide (MnO) nanoparticles (NPs) were synthesized from watermelon seed extract by the green synthesis method. The watermelon seed shell, which is left as waste to the environment, has been transformed into a product with high added value. The particle sizes of CuO and MnO NPs were determined to be in the range of 15–97 and 6–51 nm, respectively. The photocatalytic performance of the CuO and MnO NPs used as catalysts were investigated for the photocatalytic reduction of methylene blue in an aqueous solution. In the photocatalytic reduction of methylene blue, sodium borohydride (NaBH4) was used as the reducing agent. The CuO and MnO NPs were capable to remove 96.58% (in 70 min) and 96.60% (in 140 min) of methylene blue, respectively. It was determined that UV light was effective in the photocatalytic reduction of methylene blue with NaBH4. The reaction rate coefficient for the photocatalytic reduction of methylene blue with CuO and MnO NPs was calculated as 0.0426 and 0.0235 min−1, respectively. [ABSTRACT FROM AUTHOR]

Recently, transition metal carbide or nitride (MXene)-based nanomaterials have been broadly investigated as new photocatalysts and electrocatalysts for the reduction of CO2 into valuable energy-rich fuels due to their unique properties such as rich surface chemistries, flexible morphologies, bandgap structures, considerable electrical conductivities, thermal stabilities, and significant specific surface areas. Nevertheless, only a few reviews have been reported on the application of MXenes or MXene-based nanomaterials as advanced photocatalysts and/or electrocatalysts for CO2 reduction, which do not cover new findings and the current development in the application of MXene-based nanomaterials for CO2 reduction. Accordingly, herein, we present a comprehensive review of current findings on the photocatalytic and electrocatalytic reduction of CO2 by various MXene-based nanomaterials. Particularly, this review focuses on the (i) photocatalytic reduction of CO2 by functionalized Ti3C2, TiO2/Ti3C2, g-C3N4/Ti3C2, and other/Ti3C2 catalysts, (ii) electrocatalytic CO2 reduction; (iii) CO2 reduction associated with photothermal catalysis and hydrogenation, and (iv) stability of MXene-based photoelectrocatalysts. Additionally, we have briefly explored the challenges in the large-scale fabrication of MXene-based nanomaterials and proposed the future research prospects of MXene-based nanomaterials. [ABSTRACT FROM AUTHOR]

The ever-increasing energy demand has resulted in an increase in CO2 emissions and global warming. Photocatalytic reduction of CO2 to methanol, which is considered to be the next generation alternate fuel is gaining interest to combat global warming and to move towards a methanol economy. The present work focuses on photocatalytic reduction of CO2 using Polyaniline/CuO (PANI/CuO) nanocomposite to methanol, formic acid, and formaldehyde under visible light irradiation. CuO nanoparticles were synthesised using the aqueous extract of Tectona grandis (teak) leaves and further used in the synthesis of PANI/CuO nanocomposite with different CuO loading. PANI/CuO nanocomposite exhibited visible light activity in the reduction of CO2 to form methanol, formic acid, and formaldehyde. Photocatalytic reduction of CO2 with PANI/CuO nanocomposite containing 13.7% by weight of CuO resulted in a maximum yield of methanol. The band gap energy of the nanocomposite was found to be 2.28 eV, thus confirming its good visible light activity and the PANI-CuO heterojunction-based mechanism of photocatalysis is proposed. The synthesis of PANI-CuO photocatalyst uses CuO which is synthesised by an eco-friendly route with the utilisation of teak leaves, a timber industry waste and thus it can serve as a greener catalyst. [ABSTRACT FROM AUTHOR]

Novel magnetically separable BiOBr/BiFeO3 heterostructures were fabricated via a facile in situ hydrothermal chemical etching process using cetyltrimethyl-ammonium bromide (CTAB) and sulphuric acid as etching agents to react with BiFeO3 particles. The effects of solution pH and CTAB amount on the structure, morphology, and optical properties of the as-prepared samples were investigated. It was found that the best acidity of solution is pH = 3.0 for the formation of BiOBr/BiFeO3 heterostructures from BiFeO3 powder. Their photocatalytic activities and anti-photocorrosion behaviour were measured by the photocatalytical reduction of heavy metal ion Cr (VI) under visible-light irradiation. Experimental results show that the molar ratio of BiOBr to BiFeO3 contributed to different morphologies and photocatalytic activities of BiOBr/BiFeO3 composites. The optimised molar ratio in BiOBr/BiFeO3 composites was found to be 1:1. The photocatalytic reduction rate of Cr(VI) over 1:1 BiOBr/BiFeO3 composites was found to be 4.9 and 3.0 times higher than that of pure BiFeO3 and BiOBr, respectively. The hybridisation of BiOBr with BiFeO3 can markedly inhibit the photocorrosion of semiconductor BiFeO3. No obvious catalytic activity decrement can be found after five consecutive photocatalytic Cr (VI) reduction, which demonstrates the high structural stability of 1:1 BiOBr/BiFeO3. Furthermore, a possible photogenerated charge transfer process was proposed. The obviously enhanced photocatalytic activity could be ascribed to the formation of BiOBr-BiFeO3 heterojunction, accelerating the effective separation of photoexcited electron−hole pairs. This study suggests that the magnetically separable BiOBr/BiFeO3 heterostructures can be a promising photocatalyst for environment-related applications. [ABSTRACT FROM AUTHOR]

Trichloroacetic acid (TCAA) is considered as one of the major of water chlorination by-products. The present work demonstrates decomposition, mineralisation and dechlorination of TCAA by photocatalytic reduction using F doped TiO2. In this regard, the effects of various operational factors including F-TiO2 dose, the initial concentration of TCAA, photo-reaction time and solution pH were examined on the process efficiency. Based on the results, H C O 3 − , P O 4 − 3 , S O 4 − 2 , C l − and C O 3 − 2 , as the common anions in water, had no considerable impact on the TCAA degradation efficiency. Decomposition and mineralisation rate of TCAA by MeOH/UV/F-TiO2process under the optimum conditions (catalyst dosage of 0.34 g L−1, the contact time of 76 min, TCAA content of 1 mg L−1 and pH of 7.9) were found to be 97.1% and 68%, respectively. The decomposition intermediates of TCAAdetected by LC/MS and LC-MS/MStechniques were non-chlorinated compounds, mainly formic and acetic acids. It can be concluded thatMeOH/UV/F-TiO2processcan use as low energy and efficiently treatment method for the degradation of TCAA contaminated water and wastewater. [ABSTRACT FROM AUTHOR]

The unique ability of tungsten oxide (WO3) to absorb light in the visible region with a spectral range of 480 nm and longer has drawn a lot of attention. It has various advantages, including low cost, low toxicity, easy availability, recyclability, and chemical stability. There have been a number of recent applications for WO3-based catalysts and photocatalysts, such as the degradation of organic pollutants, hydrogen evolution, heavy metal treatment, CO2 photoreduction, self-cleaning, air purification, etc. For organic processes such as cross-coupling, oxidation reactions, and heterocycle synthesis, we evaluate the literature on WO3-based catalysts or photocatalysts and the mechanisms involved in these reactions. We hope that this short review will help researchers make high-performance and cheap WO3-based catalysts that can be used in a lot of organic processes. [ABSTRACT FROM AUTHOR]

In the present study, a two-step hydrothermal method was employed to synthesize Fe2O3/WS2 composites with flower-like structure, which performed significant photocatalytic activities compared with the bare components. The morphologies and structures of the as-prepared photocatalysts were characterized, as well as the surface chemical components and the optical properties. Afterwards, the photocatalytic properties of the catalysts were evaluated through degrading MB dye and reducing Cr (VI) under the simulated solar-driven irradiation. Among these photocatalysts, 2WF behaved an efficiently oxidation degradation of 20 mg/L MB solution within 20 min, more than 5 times of bare Fe2O3 nanoparticles and nearly 3 times of bare WS2 nanosheets. Besides that, it exhibited an excellent photocatalytic reduction activity on reducing 40 mg/L Cr (VI) solution within 80 min, which was far superior to bare Fe2O3 and WS2. The excellent photocatalytic oxidation and reduction abilities enabled Fe2O3/WS2 heterostructures to be applied in the field of organic and inorganic pollutant decontaminations. [ABSTRACT FROM AUTHOR]

Oxyanions-nitrate, bromate, and perchlorate in water bodies can do harms of different levels to human health. Photocatalytic reduction is one of the most promising and effective means to convert them into harmless ions. In this article, we discuss the photocatalytic mechanisms of TiO2 catalyst in nitrogen removal process. The factors determining the catalytic activity and the selectivity of nitrogen are elaborated. An overview of the pathway of photocatalysis toward bromate and perchlorate reduction is presented, and the reduction performance of different photocatalysts is evaluated. It is of vital importance to the development of low-cost photocatalytic materials and the use of their activities. [ABSTRACT FROM AUTHOR]

In this manuscript, a new hybrid nanocatalyst (PMo10Ni2/ZnS@CS) based on di-substituted heteropolyanion (PMo10Ni2) and ZnS quantum dot was synthesized via the hydrothermal method. PMo10Ni2/ZnS@CS is a candidate for removal of environmental pollutants. The synthesized hybrid nanocatalyst was analyzed by TEM, UV-vis, FT-IR, XRD, and EDX techniques. The results of XRD analysis showed the average crystallite size of the PMo10Ni2/ZnS@CS nanocomposite particles is about 33 nm, which was consistent with the TEM results. The nano-catalytic activity of PMo10Ni2/ZnS@CS hybrid nanocomposite was investigated in photocatalytic decolorization of organic dyes. The experimental results showed that the inorganic-organic hybrid nanocomposite (PMo10Ni2/ZnS@CS) had excellent photocatalytic efficiency with 98% dye removal. The recovery of the photocatalyst in the decolorization process was investigated and the results indicate a reduction of photocatalytic power after the second and third stage recovery, respectively. In the present study, PMo10Ni2/ZnS@CS was proposed as a heterogeneous nanocatalyst with broad nanocatalytic applications of dye removal. [ABSTRACT FROM AUTHOR]

Two new coordination polymers constructed from 5-sulfoisophthalic acid sodium salt (NaH2SIPA) and Co or Cu cations, [Co3(SIPA)2(4,4′-bpy)4(H2O)6]·4H2O (1) and [Cu6O3(HSIPA)3(4,4′-bpy)6(H2O)3]·7H2O (2), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), IR spectroscopy, thermogravimetric analysis, UV-Vis spectroscopy, and elemental analysis. Compound 1 represents a twofold-interpenetrating 3-D framework based on Co, SIPA, and 4,4′-bipyridine ligands with a qzd topology. Different from 1, compound 2 shows a 3-D self-penetrating framework based on Cu, HSIPA, and 4,4′-bipyridine ligands. Furthermore, the photocatalytic performance in reduction of CO2 of 1 under visible light was investigated. [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 present study, green synthesis of silver nanoparticles (Ag NPs) was synthesized from silver ions using the reducing agents of Catharanthus roseus flowers extract. This flower was extract and fractionated by non-polar to polar solvent using separating funnel. The distilled water fraction was analyses the primary phytochemical test and used the synthesis of NPs. The UV-vis spectra wavelength value at 447 nm was confirmed the product of Ag NPs. FTIR spectrum wavenumbers at 3401 and 1625 cm−1 has indicates the hydroxyl and carbonyl groups, respectively, capping the Ag NPs. HRTEM images of Ag NPs shows the spherical shape with sizes 5–20 nm. This NPs has excellent photocatalyst in the reduction of methyl orange and 4-nitrophenol (4-NP) in the presence of NaBH4. These NPs has potential antioxidant activity of DPPH, and H2O2 assays against the standard ascorbic acid contain the 100 µg/ml of NPs shows 65% and 77% of inhibition activity. [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]

The photocatalytic reduction of toxic Cr(VI) to non-pernicious Cr(III) using ZnFe2O4/EDTA (ethylenediaminetetraacetic acid) under UV irradiation was evaluated. The reduction of Cr(VI) with bare ZnFe2O4 under UV irradiation was negligible. However, the Cr(VI) in the solution was completely reduced within 3 h after the introduction of EDTA. EDTA could consume valence band holes and could be oxidized by holes into inorganic products. Therefore, photo-generated electrons could be used to reduce Cr(VI) to Cr(III). The effect of concentration of EDTA, ZnFe2O4 photocatalyst dosages, and initial pH on the photocatalytic reduction of Cr(VI) was investigated. The results revealed that the photocatalytic reduction of Cr(VI) accelerated by increasing EDTA concentration and ZnFe2O4 dosage. The present reduction process confirms the pseudo-first-order kinetic reaction. The quasi reduction rate constant increased from 3.5 x 10−4 min−1 to 2.6 x 10−2 min−1 with the increase in initial EDTA concentration from 0 to 1000 mg L−1. The acidic solution is preferable for the photocatalytic reduction of Cr(VI). The entire reduction of Cr(VI) was carried out within 2 h under the optimum conditions with pH 2, 20 mg ZnFe2O4, and 500 mg L−1 EDTA. The formation of [Cr–EDTA]3+ complex may be advantageous to accelerate the Cr(VI) reduction. A probable mechanism for the photocatalytic Cr(VI) reduction was speculated here. [ABSTRACT FROM AUTHOR]

In this study, zinc ferrite nanoparticles (ZF-NPs) were synthesized using aqueous seed extract of Piper nigrum as a bio-reducing and stabilizing agent. FTIR, SEM, FE-SEM, XRD, and TGA have been used for characterizing ZF-NPs. The results showed that Piper nigrum stabilized ZF-NPs have high purity and size range of 60–80 nm. The performance of the ZF-NPs has been investigated by photocatalytic reduction of methylene blue (MB) in the presence of sunlight. The factors responsible for affecting the degradation values of the reaction were also explored for developing a better understanding of the phenomenon. [ABSTRACT FROM AUTHOR]

Herein, we report a novel composite material of Nb2O5@MIL–125 that exhibited enhanced photoreduction of hexavalent chromium. The composite material was fabricated through an impregnation approach, which comprised of a two-step hydrothermal synthesis. As-prepared Nb2O5 nanospheres exhibited very poor charge separation; MIL–125 (Ti) which is a Ti-based metal-organic framework was introduced into the lattice of the spheres to improve charge recombination rate. The synthesized material's phase, crystallinity, textural and morphological studies were investigated utilizing XRD, Raman, TEM, SEM, and EDS, respectively. While the optical and photoelectrochemical behavior of the samples were obtained from UV–vis–DRS, PL, and EIS data. This data combined, illustrated the successful formation of a functional and effective heterointerface between Nb2O5 and MIL–125 (Ti). Ti introduced as the MOF in the lattice of Nb2O5 had an essential synergetic effect as the composite bearing the highest mole ratio of Ti showed higher effective photoreduction of hexavalent chromium. This was further complemented the PL and XPS data which highlighted the Nb–MIL–125 (2–3) composite to have excellent charge separation and rapid photoreduction of chromium. [ABSTRACT FROM AUTHOR]

The one-step method for graphene oxide (GO) simultaneous reduction and carboxylation via ultraviolet irradiation in the inert atmosphere has been reported. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) data revealed that the proposed approach allows to obtain reduced graphene oxide (rGO) films, containing up to 10 at.% of carboxyl groups. The carboxyl groups concentration can be tuned within the range of 3 to 10 at.% by controlling the oxidation degree of the irradiated GO via the preliminary low-temperature air heating. Furthermore, no carboxylation effect is observed in the case of irradiation of the completely reduced GO films. This coincides with our previous results, validating the proposed model of GO carboxylation based on photoinduced conversion of basal-plane hydroxyl groups and ketones into carboxyl ones. Despite a different degree of carboxylation, all the obtained samples demonstrate almost complete elimination of basal plane groups and restoration of the graphene flakes aromatic structure. This fact is emphasized by the sheet resistance measurements, demonstrating that the obtained C-xy graphene exhibits high electrical conductivity. As a net result, the material obtained by the presented method shows promising applications in the manufacturing of biosensor transducers owing to both its conductive nature and presence of carboxyl groups, playing the role of the anchoring points for biomolecules. [ABSTRACT FROM AUTHOR]

Sulfoxides, upon irradiation with ultraviolet (UV) light undergo α-cleavage, hydrogen abstraction, photodeoxygenation, bimolecular photoreduction, and stereo-mutation. The UV irradiation of dibenzothiophene S-oxide (DBTO) yields dibenzothiophene (DBT) as a major product along with ground-state atomic oxygen [O(3P)]. This is a common method for generating O(3P) in solution. The low quantum yield of photodeoxygenation and the requirement of UVA light are drawbacks of using this method. The sulfoxides benzo[b]naphtho-[1,2,d]thiophene S-oxide, benzo[b]naphtho [2,1,d]thiophene S-oxide, benzo[b] phenanthro[9,10-d]thiophene S-oxide, dinaphtho- [2,1-b:1',2'-d]thiophene S-oxide, and dinaphtho[1,2-b:2',1'-d]thiophene S-oxide have shown to deoxygenate up to three times faster than DBTO upon UVA irradiation; however, the photodeoxygenation of these sulfoxides does not appear to be limited to the production of O(3P). In this work, phenanthro[4,5-bcd]thiophene S-oxide, triphenyleno[1,12-bcd]thiophene-S-oxide, and perylo[1,12-bcd]thiophene-S-oxide were synthesized and their photodeoxygenation was studied. Phenanthro[4,5-bcd]thiophene-S-oxide, triphenyleno[1,12-bcd]thiophene-S-oxide, and perylo[1,12-bcd]thiophene-S-oxide deoxygenated upon UVA irradiation. However, the common intermediate experiments did not conclusively identify the photodeoxygenation mechanism of these sulfoxides. [ABSTRACT FROM AUTHOR]

Photocatalytic reduction of CO2 is known as one of the most promising methods to produce valuable fuels and value-added compounds. To overcome selectivity and efficiency downsides, various photocatalysts have been designed and developed. This review discusses the state-of-the-art in photo-conversion of CO2 over graphitic carbon nitride (g-C3N4)-based composites. The modification strategies to improve photocatalytic activity of g-C3N4 were classified into different categories and discussed as structural modifications, elemental doping, copolymerization, fabricating heterojunctions between g-C3N4 and other semiconductors, Z-scheme heterojunctions, noble metal/g-C3N4 photocatalysts, and design of ternary nanocomposites based on g-C3N4. Finally, perspectives and future research works in this field were also outlined. [ABSTRACT FROM AUTHOR]

Although it is well known that viologen radical cations can self-assemble into stacks or complexes on account of radical-radical pairing interactions, it has only recently been demonstrated that reduction of main-chain polyviologens integrated into hydrogel networks can trigger actuation. In these earlier examples, hydrogels comprising oligoethylene glycol-based polyviologens and poly(ethylene glycol) were functionalized with terminal azide groups to prepare 'click'-based gels. Here, we report a new structural design for the functional polyviologen that consists of main-chain viologen subunits separated by hexamethylene groups instead of glycols and is capped at each end with styrene groups. Activation of this viologen-based macrocrosslinker was achieved using chemical- and photoreduction methods and its ability to undergo intramolecular chain-folding was monitored by absorption spectroscopy. Acrylate-based organogels and hydrogels were also prepared and a comparison was carried out to assess the actuator performance in each gel in terms of the rate of contraction and changes in stiffness. [ABSTRACT FROM AUTHOR]

In order to enhance the adhesion strength between the PI film and the electroless copper film, a combination of swelling and TiO2 photocatalytic treatments was used to modify polyimide (PI) film. The effects of the swelling solution composition and TiO2 photocatalytic condition on the surface performance were investigated. After the optimal swelling and photocatalytic treatment, the surface contact angle of the PI film decreased from 85 to 28.7°, and the surface average roughness of the PI film only increased from 1.3 to 13.6 nm, indicating no obvious change for the surface topography of PI film after the photocatalytic treatment. However, the adhesion strength between electroless copper film and the PI film reached to 0.6 KN·m−1. The FT-IR spectra and XPS analyses indicated that -COOH group was formed on the PI surface after the treatment, and the surface hydrophilicity was improved, which improved the adhesion strength between the PI film and the electroless copper film. [ABSTRACT FROM AUTHOR]

A facial route to synthesize a new composite material that consists of TiO2 nanoparticles grown over the Cu2Se-graphene (Cu2Se-G) through ultrasonic techniques was reported, which was characterized through some general analyses. The photoreduction of CO2 to CH3OH performance of the Cu2Se-graphene-TiO2 (Cu2Se-G-TiO2) nanocomposite was tested with GC (GCMS-QP2010 SE) under UV and visible light. Our excellent results indicate strong reduction rates of CO2 compared to original TiO2 and binary Cu2Se-G. We explain in our study the scavenger effect and the mechanism from CO2 to CH3OH. [ABSTRACT FROM AUTHOR]

Bi4Ti3O12 nanoparticles with size of 60-90 nm were decorated with smaller-sized Ag nanoparticles (12-25 nm) by a photocatalytic reduction method. The as-prepared Ag-Bi4Ti3O12 composites were systematically characterised by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, photoluminescence spectroscopy and photocurrent response. It is demonstrated that the decoration of Bi4Ti3O12 with Ag nanoparticles leads to an effective separation of photogenerated electron-hole pairs. RhB was chosen as the target organic pollutant to evaluate its degradation behaviour over Ag-Bi4Ti3O12 composites under simulated sunlight irradiation. Compared to bare Bi4Ti3O12, Ag-Bi4Ti3O12 composites exhibit a significantly enhanced photocatalytic activity and the highest photocatalytic activity is observed for 5·2 wt% Ag-Bi4Ti3O12. The first-order reaction rate constant suggests that the photocatalytic activity of 5·2 wt% Ag-Bi4Ti3O12 is about 2·4 times higher than that of bare Bi4Ti3O12. AO, ethanol and BQ were, respectively, used as the scavengers of h+, •OH and •O-2 to investigate their effect on the degradation of RhB. It is found that only AO has an important suppression on the dye degradation, from which it is concluded that h+ is the dominant reactive species causing the dye degradation. [ABSTRACT FROM AUTHOR]

Large-area ZnO nanorod arrays have been synthesised on a stainless steel grid by two-step growth approach, including the synthesis of seed layer and growth of ZnO nanorods in aqueous solution. X-ray diffraction analysis and energy dispersive X-ray elemental mapping measurements indicate wurtzite ZnO structures are formed. Scanning electron microscopy shows high uniform coverage of the densely packed ZnO nanorod arrays are grown on the stainless steel grid frame, and the as-grown ZnO nanorods have uniform diameters. Meanwhile, the ZnO nanostructures also show good optical quality and photocatalytic activity. The results show using the stainless steel grid as substrate will provide a promising way of producing large-scale nanorod arrays with good controllability and morphologies. And it will be critical in potential application such as high-efficiency filtering and catalysts. [ABSTRACT FROM PUBLISHER]

Mesoporous TiO2was synthesized by sol-gel method and mechanically mixed with functionalized multiwall carbon nanotubes which decorated by different amount of Ag. Nanocomposite was characterized by X-ray Diffraction, Scanning Electron Microscopy/Transmission Electron Microscopy, Brunauer–Emmett–Teller, Fourier Transform Infrared Spectroscopy, Atomic Absorption Spectroscopy, UV–Visible Diffuse Reflectance Spectroscopy, and UV–Vis Absorption Spectroscopy. The photoactivity of nanocomposite containing mesoporous TiO2, multiwall carbon nanotubes (MWCNT), and Ag was evaluated by the degradation of methyl orange in aqueous solution under UV irradiation. Results showed that the MWCNT that decorated with the 15.5% of Ag facilitates the photocatalytic activity of mesoporous TiO2. [ABSTRACT FROM PUBLISHER]

ZnS photocatalyst is stabilized with different amounts of cetyltrimethylammoniumbromide on Montmorillonite and acid-activated Montmorillonite (AAMMT). These catalysts were investigated for the photocatalytic reduction of carbon dioxide to methane, they were prepared via a simple solution method with different amounts of cetyltrimethylammoniumbromide (CTAB) stabilizer to examine its effects on the basal spacing, reaction kinetics, and products yield. Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), and X-ray diffraction (XRD) tests were performed on the catalyst to characterize it. The average yield of hydrogen and methane in AAMMT samples was found to be higher than in Montmorillonites (MMT) samples, which was regarded as a consequence of the higher active area and the optimum amount of CTAB. [ABSTRACT FROM PUBLISHER]

ZnO nanoparticles were prepared through the chemical precipitation method and immobilized on glass plates. The effects of initial pH, UV lamp power, glass surface area, and initial humic substances (HS) concentration on the photocatalysis of HS were studied. Acidic conditions favoured the photocatalysis of HS. The degradation efficiency of HS was enhanced by increasing the UV lamp power and glass surface area. According to the results of total organic carbon (TOC) analysis, a mineralization efficiency of 59.3% was obtained within a reaction time of 120 min in comparison with the removal efficiency (%) of UV254, which was found to be 83.3%. [ABSTRACT FROM PUBLISHER]

ZnO, CeO2, TiO2, ZnO-CeO2(ZC), CeO2-TiO2, ZnO-TiO2(ZT) and ZnO-CeO2-TiO2(ZCT) powders were fabricated using a combustion synthesis (CS) method for applying to photo-degradation and decoloration of Methyl blue with them as catalysts. Ascorbic acid (C6H8O6) and nitrate were used as fuel and raw materials, respectively. The powder was obtained when the processing parameters were optimized. C6H8O6as fuel was used for the preparation of ZnO, CeO2, TiO2, ZC, CT, ZT and ZCT powders. The produced particles were characterized using scanning electron microscopy (SEM) for the particle morphology, UV for absorbent properties, IR for purity of sample, and XRD for phase, particle size and crystallinity of the samples. In addition, these particles showed good photocatalytic and decolorizing activity, which provided an opportunity for these materials to be used for the degradation and decoloration of Methyl blue. [ABSTRACT FROM AUTHOR]

GR–TiO2nanocomposite was prepared by simple chemical method using graphene oxide and titanium isopropoxide (Ti [OCH (CH3)2]4) precursors. The crystalline nature of the composite was characterised by powder X-ray diffraction and the intercalation was explained by Raman spectroscopy. The morphology of the composite was analysed by field emission scanning electron microscopy. The elemental and quantitative measurement of the composite was determined by electron dispersive spectroscopy. The shape and size of the particle was measured by transmission electron spectroscopy and high resolution spectroscopy. The surface area and elemental composition of the composite was studied by using Brunauer–Emmett–Teller (BET) method and X-ray photoelectron spectroscopy. Photo-generated electrons were studied by photoluminescence spectra. The photocatalytic activity of nanocomposite was investigated by the degradation of Rhodamine-B (Rh-B) in an aqueous solution under solar light irradiation. The GR–TiO2demonstrates photocatalytic activity in the degradation with a removal rate of 98% under solar light irradiation as compared with pure TiO2(42%), graphite oxide (19%), and mechanical mixture GR + TiO2(60%) due to the increased light absorption intensity and reduction of electron–hole pair recombination with the intercalation of graphene and TiO2. The results indicated that the GR–TiO2could be used as a catalyst to degrade Rh-B from coloured wastewater. [ABSTRACT FROM PUBLISHER]

Water pollution by organic pollutants is an ever-increasing problem for the global concerns. Some recently published papers are reviewed and summarized with the focus being on the photocatalytic oxidation of tetracycline in wastewater effluent. In this review, the effects of various operating parameters on the photocatalytic degradation of tetracycline are presented. Recent findings suggested that type of photocatalyst and composition, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, and oxidizing agents/electron acceptors can play an important role on the photocatalytic degradation of tetracycline. [ABSTRACT FROM AUTHOR]

In this paper, maghemite (γ-Fe2O3) and titanium oxide (TiO2) nanoparticles were synthesized by hydrothermal and coprecipitation methods, respectively. These nanoparticles were combined together in various ratios (1:10, 1:20, 1:60, 1:80, and 1) and embedded in polyvinyl alcohol (PVA)-alginate beads. These beads were tested for photocatalytic behavior in eliminating toxic Pb(II) from the aqueous solution. The photocatalytic experiments were performed under sunlight irradiation and without sunlight. Several operating conditions such as initial Pb(II) concentration, pH, contact time, and TiO2: γ-Fe2O3ratios were investigated to evaluate their effect on the process. The recycling attributes of these beads were also investigated. The results revealed that 100% of the Pb(II) was eliminated in 100 min at pH 7 under sunlight when the ratio of TiO2:γ-Fe2O3was kept to 1. The PVA-alginate maghemite and titania beads showed better efficiency for Pb(II) removal than PVA-alginate titania beads and PVA-alginate maghemite beads. X-ray photoelectron spectroscopy (XPS) analysis also revealed that Pb(II) removal was via photocatalytic reduction due to the presence of Pb(0) in the high-resolution scan at 130–160 eV. Also, the PVA-alginate titania and maghemite beads can be readily isolated from the aqueous solution after the photocatalytic process and reused for at least 6 times without significant losses in their initial properties. The reduction of Pb(II) with PVA-alginate titania and maghemite beads fitted the Langmuir–Hinshelwood (L–H) kinetic model at a correlation coefficient (R2) of 0.9923. [ABSTRACT FROM AUTHOR]

The complexation ability of photoreduction products of 2-(2,5-di-tert-butyl-3,4-dioxycyclohexa-1,5-dienyl)ethyl methacrylate in tetrahydrofuran (THF) solution and in its copolymer films with dimethacrylate and ethylene glycol monomethacrylate was studied. The product of photochemical reduction – catechol – reacts with (NH4)6Mo7O24·4H2O, NH4VO3and (NH4)2Fe(SO4)2with the formation of corresponding metal complexes in solution and in the polymer bulk. The concentration of the molybdenum complexes in the polymer matrix was proportional to the exposure and holding time in solution of molybdate salt. Polymer film with optically controlled distribution ofo-quinonemethacrylate molybdenum complexes was prepared. A film containing antimony and molybdenum complexes together in the polymer structure in predetermined ratio was obtained by sequential treatment of irradiated copolymer film (50% conversion) by THF solution of SbPh3, and water solution of (NH4)6Mo7O24·4H2O. [ABSTRACT FROM AUTHOR]

The potential risks of nano-materials and the spread of antibiotic resistance genes (ARGs) have become two major global public concerns. Studies have confirmed that nano-alumina can promote the spread of ARGs mediated by plasmids. Nano-titanium dioxide (TiO2), an excellent photocatalytic nano-material, has been widely used and is often present in aqueous environments. At various nano-material concentrations, bacterial density, matting time, and matting temperature, nano-TiO2 can significantly promote the conjugation of RP4 plasmid in Escherichia coli. We developed a mathematical model to quantitatively describe the conjugation process and used this model to evaluate the effects of nano-TiO2 on the spread of ARGs. We obtained analytical solutions for total and resistant bacteria, which were enumerated by the abundance of genetic loci unique to the plasmid and the chromosome using qPCR. Our results showed that the mathematic model was able to fit the experimental data well and can be used to quantitatively evaluate the effects of nano-TiO2. According to our model, the presence of nano-TiO2 decreased the bacterial growth rate from 0.0360 to 0.0323 min−1 and increased the conjugative transfer rate from 6.69 × 10−12 to 3.93 × 10−10 mL cell−1 min−1. These results indicate that nano-TiO2 inhibited bacterial growth and promoted conjugation simultaneously. The data for morphology and mRNA expression also demonstrated this phenomenon. Our results confirm that environmental nano-TiO2 may cause the spread of ARGs and thus poses an environmental risk. In addition, we provide a potential method for monitoring changes in ARGs that result from conjugation and evaluating the effects of antimicrobial substances on ARG expression. [ABSTRACT FROM AUTHOR]

In this study, we report the successful reduction of graphene oxide (GO) with cost effective and environment friendly methods. In the first method, we irradiated GO with highly energetic UV laser to obtain reduced GO (rGO). Moreover, Ag and Ni nanoparticles (NPs) were also productively deposited on rGO byin situreduction of metal salts with ultraviolet (UV) laser irradiation. In the second method, we employed neem leaf extract as reducing agent to synthesise rGO decorated with Ag and Ni NPs in a one-step approach. The reduction of GO as well as the deposition of Ag and Ni NPs on rGO was examined by Raman spectroscopy. We also performed ultraviolet–visible (UV-vis) spectroscopy, X-ray diffraction and SEM analysis to observe absorption in UV-vis range, crystallographic orientations and surface morphology of rGO-NPs composites respectively. Both the reducing sources were found efficient for the reduction of GO and successful deposition of metal NPs on the surface of rGO viain situreduction of metal salts. However, UV laser irradiation mediated reduction of GO was better relative to the neem leaf extract. [ABSTRACT FROM AUTHOR]

Cu2O/TiO2thin film is obtained by electrodeposition method. The structure and optical properties of thin film are characterised using X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), SEM, Raman, PL and ultraviolet visible spectrophotometer (UV-Vis). Photocatalytic performance of Cu2O/TiO2thin film and degradation pathways for methylene blue (MB) is also investigated in this paper. The results indicate that the pure Cu2O/TiO2thin film with the (111) preferential orientation shows a high photocatalytic activity, whose crystal structure exhibits high quality and is characterised by novel Raman optical properties of nanometre spherical morphology. PL and UV-Vis results indicate that Cu2O/TiO2thin film has an obvious absorption and photoelectric response at the visible light range. After 300°C annealing treatment for the film, the intensity peak of (111) crystal plane and UV-Vis absorption intensity have enhanced 60 and 50%, respectively. The reaction rate constant and photoluminescence intensity are 2.8 and 3.4 times as high as those before annealing treatment. The separated efficiency of electron-hole pairs is increased. More than 99.9% of MB can be degraded in 3 h by Cu2O/TiO2thin film. Moreover, MB molecule can be decomposed completely. Recycling use of the catalyst has revealed that the film can be reused for 18 times. [ABSTRACT FROM AUTHOR]

In this study, we report the successful reduction of graphene oxide (GO) with cost effective and environment friendly methods. In the first method, we irradiated GO with highly energetic UV laser to obtain reduced GO (rGO). Moreover, Ag and Ni nanoparticles (NPs) were also productively deposited on rGO byin situreduction of metal salts with ultraviolet (UV) laser irradiation. In the second method, we employed neem leaf extract as reducing agent to synthesise rGO decorated with Ag and Ni NPs in a one-step approach. The reduction of GO as well as the deposition of Ag and Ni NPs on rGO was examined by Raman spectroscopy. We also performed ultraviolet–visible (UV-vis) spectroscopy, X-ray diffraction and SEM analysis to observe absorption in UV-vis range, crystallographic orientations and surface morphology of rGO-NPs composites respectively. Both the reducing sources were found efficient for the reduction of GO and successful deposition of metal NPs on the surface of rGO viain situreduction of metal salts. However, UV laser irradiation mediated reduction of GO was better relative to the neem leaf extract. [ABSTRACT FROM AUTHOR]

We reported a green and simple method for biosynthesizing zinc oxide nanoparticles (ZnO NPs) usingCorymbia citriodoraleaf extract as reducing and stabilizing agent. SEM, EDX, XRD, UV–VIS spectroscopy, Raman spectroscopy and TGA have been used for characterizing the biosynthesized ZnO NPs. The results indicating the ZnO NPs synthesized byC. citriodoraleaf extract have high purity and the average size is 64 nm. The photocatalytic activity of the ZnO NPs has been investigated by degradation methylene blue under visible light irradiation. Due to the smaller size, the biosynthesized ZnO NPs showed an excellent photocatalytic performance. [ABSTRACT FROM PUBLISHER]

Poly(aniline-co-o-toluidine) encapsulated zinc oxide (ZnO) nanocomposite was prepared by chemical oxidative polymerization. The composition, morphology and structure of poly(Ani-co-oT)/ZnO nanocomposite were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and UV-visible spectroscopy (UV-vis). FTIR spectrum endorsed the formation of nanocomposite. TEM image showed that the ZnO nanoparticles were well dispersed in the copolymer matrix. XRD results revealed that the crystallinity of copolymer was more pronounced after the addition of ZnO. TGA results illustrated that the decomposition temperature of nanocomposite was higher than the pure copolymer. Electrical conductivity of the copolymer was increased by the addition ZnO. In addition, the photocatalytic reaction with illuminated nanocomposite can be effectively applied to treat wastewater contaminated with Cr(VI). The reduction pattern of Cr(VI) was better fit to first-order kinetic model. The nanocomposite was also applied as a photocatalyst for the degradation of methylene blue (MB) dye. [ABSTRACT FROM PUBLISHER]

The photocatalytic degradation of acephate was investigated using Ce-doped TiO2(TiO2/Ce) hydrosol. In contrast to previous research conducted under artificial light in the laboratory, this study investigated the decomposition of acephate in a field trial. The results show that acephate can be efficiently degraded by the TiO2/Ce system under natural field conditions; the degradation efficiency was affected by the dosage of the photocatalyst and acephate. The optimum dosage of TiO2/Ce was 2400 g a.i.ha−1, and the photodegradation efficiency of acephate reached 93.5% after 20 h at an acephate dosage of 675 g a.i.ha−1. Ultra-performance liquid chromatography/mass spectrometry (UPLC/MS) analysis detected and identified four degradation products—methamidophos, phosphorothioic acid O,O,S-trimethyl ester, S-methyl methanethiosulfonate and phosphorous acid—that were formed during the TiO2/Ce photodegradation of acephate. Based on the structural identification of the degradation products, a probable photodegradation pathway was proposed, and the first decomposition step may be the cleavage of the C‒N bond of acephate. Subsequently, the P‒S and P‒O bonds may be oxidized gradually or simultaneously to complete the mineralization. [ABSTRACT FROM AUTHOR]

The photochemical behavior of 2-azidopurine 2′,3′,5′-tri-O-acetylribonucleoside has been investigated in aqueous solution under aerobic and anaerobic conditions. The two major processes under anaerobic irradiation of 2-azidopurine 2′,3′,5′-tri-O-acetylribonucleoside involve unprecedented transformation into 1-(5′-O-acetyl-β-D-ribofuranosyl)-5-[(2-oxo-1,3,5-oxadiazocan-4-ylidene)amino]-1H-imidazole-4-carbaldehyde and photoreduction to respective 2-aminopurine derivative, whereas under aerobic conditions these two processes occur to a much lesser extent and photooxidation to respective 2-nitropurine derivative dominates. The structures of photoproducts formed were confirmed by NMR and high-resolution electrospray ionization mass spectral data. [ABSTRACT FROM PUBLISHER]

The feasibility of Cu(II) removal by photoreduction using maghemite polyvinylalcohol-alginate beads was investigated. Photoreduction experiments were performed to investigate the influence of initial concentration and pH on the removal of copper(II) metallic ions. The fate of Cu(II) during the photoreduction process was investigated using the X-ray photoelectron spectroscopy. It was observed that the Cu(II) removal rate was faster under sunlight than without sunlight due to the reduction process of Cu(II) to Cu(I). The photoreduction results showed that the adsorption of Cu(II) ions followed a Langmuir Hinshelwood model with the photoreduction rate constant and adsorption coefficient values of 24.1 ppm/min and 0.0098 ppm−1, respectively. [ABSTRACT FROM AUTHOR]

Graphene-TiO2was obtained by reduction of graphite oxide by the hydrothermal method. Using photocatalytic activity to reduce carbon dioxide to methanol and formic acid was investigated in this study. The results show that the graphene loading affects the absorption of light in the visible light region. A larger surface area can also improve the catalytic activity. The largest yield of methanol and formic acid, under light of 365 nm, can reach 160 and 150 μmol g−1, respectively, with 8.5% graphene loading. An increase in graphene loading can enhance photocatalytic performance, but too much will also decrease the reduction efficiency by shielding the light from reaching the catalytic surface. The effect of pH was also investigated. The mechanism of the reaction was also discussed in this study.Implications: Graphene-TiO2 hybrids were prepared by the hydrothermal method. Surface area and visible light adsorption increased with the graphene loading. Increased graphene loading improved the methanol and formic acid production. Too much graphene loading will decrease the reduction efficiency. The effect of pH shows that the HCO3− species prefers the formation of formic acid. The mechanism of the reaction was also discussed in this study. [ABSTRACT FROM PUBLISHER]

By combining ceramic membrane cross-flow filtration process with photocatalytic reaction, a photocatalytic membrane reactor was designed. The reactor was simulated, and it was confirmed that it was a continuous stirred tank reactor. Experiment results indicated that, using a ceramic membrane with mean pore size of 0·1 µm, slurry TiO2 particles with mean size of 0·27 µm could be perfectly separated and recycled in the system, and the stable removal rate of methylene blue was more than 95% with TiO2 loading of 0·5 g L−1, reaction temperature of 45°C, filtration pressure of 0·5 kg cm−2 and cross-flow velocity of 3·3 m s−1. [ABSTRACT FROM AUTHOR]

Tungsten and tungsten-carbon doped titania particles were successfully synthesised by a simple solvothermal method using WCl6 as W source and titanium tetra-n-butoxide/ethanol as C source. With the incorporation of W in TiO2 lattice, the near infrared absorption property of W-TiO2 samples was strongly promoted. Furthermore, the visible light absorption capability of TiO2 based samples was also greatly affected by codoping C in W-TiO2. More importantly, the C-W codoped TiO2 samples presented excellent continuous toxic NO gas destruction ability much superior to those of undoped TiO2, solely C and W doped TiO2 as well as commercial P25 titania under the irradiation of UV and visible lights. The near infrared absorption performance and photocatalytic activity of TiO2 based products could be effectively controlled by W doping and C-W codoping, which probably have a promising application in the field of environmental protection and near infrared light shielding. [ABSTRACT FROM AUTHOR]

Acetonitrile is a commonly used solvent in both industry and research. The treatment of acetonitrile wastes in dilute aqueous solutions with visible light offers advantages to chemical treatment and ultraviolet (UV) irradiation. This study presents the degradation of acetonitrile via a photoinduced electron transfer reaction in the presence of a photosensitizer (dye) and a sacrificial reductant under visible light. Acetonitrile photodegradation (photoreduction) was investigated utilizing a variety of sacrificial reductants and photosensitizers. Optimal results were observed in the presence of methylene green and tri-isopropanolamine with a decrease of acetonitrile in solution to 86% in 24 hours. The only photoreaction product observed was acetaldehyde and a plausible mechanism for the photochemical degradation of acetonitrile is proposed. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BiVO4) powder was prepared by the solvothermal method. Bismuth nitrate and ammonium vanadate were used as the starting precursors with mole ratio of 1:1. The mixed solution was heated in the solvothermal vessel at 100°C for 2–6 h. The phase of BiVO4powder was characterized by X–ray diffractometer (XRD). The morphology and chemical composition of BiVO4powder were investigated by scanning electron microscope (SEM) and energy dispersive X–ray spectroscope (EDXS). The surface area of BiVO4powder was determined by Brunauer, Emmett and Teller analyzer (BET). The photocatalytic degradation of phenol and chlorophenol onto BiVO4powder was studied and determined by gas chromatograph (GC). [ABSTRACT FROM AUTHOR]

We demonstrate a new method for the preparation of silver nanoparticles (AgNPs) utilising dye-sensitised photo-reduction on triple-stranded β-1,3-glucans. Reflecting the chiral helical structure of these polysaccharides, the chiral plasmonic AgNPs were yielded when hydrophobic dyes strongly interacting with the helical β-1,3-glucan main-chain were used. This system offers a new strategy to create chiral plasmonic AgNPs and a new idea to utilise helix-forming polysaccharides as a chiral template. [ABSTRACT FROM AUTHOR]

Time-resolved EPR studies of the hydrogen abstraction reaction of photoexcited xanthone in 2-propanol were carried out as a function of the concentration of xanthone and the sample temperature. The temperature was varied from 22°C to about −30°C, and the concentration from about 0.2 to 4.0 mM. At low temperature or concentration, the observed spectra of the xanthone ketyl radical and the propan-2-olyl radical could be simulated as a superposition of a hyperfine-independent component due to the emissive triplet mechanism and a hyperfine-dependent component due to the S–T0radical pair mechanism. However, with an increase in the concentration of xanthone, the relative contribution of TM decreases, and, concomitantly, the net absorptive component of only the xanthone ketyl radical increases. As the spin polarisation mechanisms do not predict any concentration dependence, this unusual behaviour is explained by invoking the enhancement of the spin–lattice relaxation rates due to Heisenberg spin exchange occurring at high local concentrations of the radicals. The net absorptive signal is attributed to thermally equilibrated radicals. The observed temperature dependence of the spin polarisation behaviour is similarly explained. The origin of the net absorptive signal in the TREPR spectra of the acetone−2-propanol system is also attributed to thermally equilibrated radicals. The self-quenching mechanism of xanthone is proposed to be an electron-transfer reaction from an excited xanthone molecule to another xanthone in the ground state. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the optimal conditions for the treatment of chromate [Cr(VI)]- contaminated water by UV photocatalysis using synthesized TiO2-coated silica granules (φ 1.7-4.0 mm) containing 12.4% of TiO2 in a batch method. The effect of the volume of the solution on Cr(VI) removal was investigated in the photocatalysis process by using 10 g of TiO2-coated silica granules in water samples with a constant initial Cr(VI) concentration of 5 mg L- 1. In a 10-mL solution, Cr(VI) concentrations were observed to decrease below the detection limit (< 0.05 mg L- 1) in 300 min. Furthermore, Cr(VI) concentrations gradually decreased with time in other solutions with larger volumes. The capacity of the UV photocatalysis process to remove Cr(VI) using 10 g of TiO2-coated granules did not fluctuate with the solution volume for samples with a constant initial Cr(VI) concentration. The lower the initial pH of the solution, the greater was the amount of Cr(VI) removed from the solution. The addition of chloride ions to the solutions accelerated the removal of Cr(VI) by UV photocatalysis. Ten grams of TiO2-coated silica granules were repeatedly used to the 300-min treatment of the Cr(VI) solution (10 mL, 6 mg L-1) till seven cycles. After four cycles of UV photocatalysis, Cr(VI) was completely removed from all the solutions. After the fifth cycle, the Cr(VI) removal capacity of the UV photocatalysis process decreased with the repeated use of the catalyst. [ABSTRACT FROM AUTHOR]