Nano-photocatalytic Materials Research Articles

Optimization of degradation of potassium ethyl xanthate using Fe2O3/TiO2/Flyash nanophotocatalyst using Taguchi statistical approach

Xanthate from mineral processing wastewater is a major threat to the ecosystem. Photocatalysis is emerging as the most effective process with the invention of new nanophotocatalytic materials. The present research focuses on developing the ternary nanocomposite Fe2O3/TiO2/Flyash by a facile hydrothermal method combined with a water bath precipitation method for the efficient degradation of potassium ethyl xanthate (KEX). Taguchi’s experimentation (L16) orthogonal array is used for the optimization of process parameters to get maximum KEX degradation efficiency. The optimized parameters are found to be calcination temperature 400 OC, photocatalyst dosage 0.7 g/L, pH 5, pollutant concentration 10 mg/L, and light intensity 100 W. The percentage contribution of each parameter is obtained through the ANOVA statistical approach as calcination temperature > pH>pollutant concentration > photocatalyst dosage > light intensity. The adsorption mechanism follows the Freundlich isotherm and fits well with pseudo-first-order and second-order kinetics. Material characterization is also done to analyze the crystal structure and morphology of the newly developed nanocomposite to gain a better understanding of the mechanism. This study indicates that the newly developed nanocomposite photocatalyst can effectively degrade potassium ethyl xanthate under light irradiation for 60 min.

Deep eutectic solvent as an effective tool for enhanced photocatalytic activity of Cu2S@MoS2 nano-assemblies: A green approach

The scientific world has witnessed the emergence of plethora of green strategies to ameliorate the efficiency of nano-photocatalytic materials for waste water treatment applications. This work, for the first time, highlights the effect of ZnCl2 and urea-based DES on the morphology, electronic band structure and photocatalytic efficiency of Cu2S @MoS2 NPs compared to solvents like water, EDA and DETA. XRD and FT-IR analysis confirmed the formation of NPs and quite significant changes in the pattern of M-S bonds of Cu2S@MoS2 were observed upon variation of solvents. The FE-SEM analysis of NPs prepared in 1:1 composition of DES and water (Cu2S@MoS2 NPs - 1:1) showed entirely distinct nanoflower morphology compared to spherical arrangement shown by NPs prepared using other solvents. As a result, Cu2S@MoS2 NPs - 1:1 showed superior textural properties with a surface area of 89 m2/g in contrast to 7.4, 6.2 and 18 m2/g observed for NPs synthesized in water, EDA and DETA, respectively. Besides, wide band gap of 2.75 eV for Cu2S@MoS2 NPs - 1:1 induced favorable charge carrier recombination kinetics, which played an instrumental role in the degradation of tetracycline hydrochloride (TC) and rhodamine B (RB). Cu2S@MoS2 NPs - 1:1 showed best photocatalytic activity as 97% and 96% of TC and RB was removed after 90 min of visible light irradiation with no significant decline in removal efficiency till 5 cycles. Scavenger studies hinted towards the crucial role of h+ and ⋅ OH in degradation process and a mechanism was proposed accordingly. The superior photocatalytic activity of NPs prepared using DES compared to water and organic solvents showed that the inclusion of DES in synthesis schemes of NPs is an excellent strategy for improving their efficiency towards waste water treatment applications.

Biomass C-doped three-dimensional Bi2WO6 for enhanced visible-light-driven photodegradation of diclofenac and rhodamine B

Photocatalysis as a green and efficient pollutant degradation technology, displaying great potential in environmental purification. By one step hydrothermal method in this study, flower-like Bi2WO6 with a large specific surface area was obtained, and the preparation of biomass carbon modified Bi2WO6 with sorghum stalks was also proposed to construct a series (BWO/x%C). The composites were effectively characterized in terms of several aspects of structure and properties. With the dyes rhodamine B and diclofenac as typical organic pollutants, the photocatalytic activity of the proposed photocatalysts was evaluated. Under visible light irradiation, the removal of rhodamine B by BWO/4%C reached 97.27% within 50 min and that of diclofenac reached 96.19% within 120 min, which were significantly favorable to single-phase Bi2WO6. The superiority of this system BWO/4%C is mainly due to its large specific surface area (33.51 m2/g), which provides additional reaction sites for contaminants. The UV–Vis DRS findings indicated that the modified biomass C reduced the band gap of Bi2WO6 and improved the availability of Bi2WO6 to visible light, and the separation efficiency of the electron and hole pairs of Bi2WO6 was improved due to the strong electron transfer ability of biomass C. The analyzing results of free radical trapping experiments confirmed that h+ and •O2- are the main active substances involved in the photodegradation reaction. The results of five cycle experiments exhibited that the degradation rate of rhodamine B still reached higher than 90%, confirming the good stability of the prepared material. Finally, a feasible degradation mechanism was proposed for the degradation of rhodamine B and diclofenac. It offers new ideas for the development of composite nano-photocatalytic materials targeting difficult-to-degrade organic pollutants.

Kinetics and mechanism of enhanced norfloxacin degradation by Fe3O4@La-BiFeO3 based on weak magnetization and efficient charge separation

Improving the yield of reactive oxygen species and inhibiting the recombination of photogenerated e- and h+ have been reliable strategies to accelerate the rate-limiting step for nano photocatalytic materials. A novel magnetic Fe3O4@La-BiFeO3 composite with variable molar ratios was successfully synthesized via a facile hydrothermal method for the photo-Fenton-like degradation of norfloxacin (NOR) under visible light irradiation. The comprehensive characterization of the crystal phase purity, morphological structure and elemental composition of the catalyst confirmed the formation of a heterojunction structure between Fe3O4 and La-BiFeO3. The effects of the composite molar ratio, initial pH, catalyst addition, and H2O2 concentration on the degradation efficiency were investigated. 20% Fe3O4@La-BiFeO3 showed the best catalytic activity with 93.8% removal of NOR after 60 min of reaction and the pseudo-first-order rate constant was 0.05952 min−1, attributed to the synergistic interaction of the photocatalytic and Fenton-like processes. The excellent stability and recyclability of the catalyst ensured the catalytic reactions continued to occur efficiently. The appropriate amount of Fe3O4 reduced the band gap of the catalyst, and the introduction of a weak magnetic field accelerated the transfer of electrons between interfaces, effectively restrained the recombination of photogenerated e-/h+ and directly enhanced the yield of ·OH and O2·-. This work not only realized the preparation of a heterogeneous photo-Fenton-like catalyst with high application potential for the degradation of antibiotics, but also provided new prospects for designing efficient catalysts on the basis of theoretical guidance.

Pumice-loaded rGO@MnO2 nanomesh photocatalyst with visible light response for rapid degradation of ciprofloxacin

The agglomeration and recycling of nano-photocatalytic materials are still a big problem restricting the practical application of photocatalytic technology. Natural porous pumice with adsorption capacity provides an innovative approach to this challenge. Herein, the pumice supported reduced graphene oxide and MnO2 (PS@rGO@MnO2) was designed as a visible-light-driven solid photocatalyst. The PS@rGO@MnO2 possessed good photocatalytic performance, and the removal rate of ciprofloxacin (CFX) reached 80.00% with simulated solar irradiation for 6 h, and the degradation rate constant was 4.2 times that of blank pumice. The degradation rates of CFX in secondary effluent, lake water, and river water can reach 62.15%, 68.33%, and 67.63%, respectively. Hole (h+) and superoxide radical (O2−) are the main reactive oxygen species. The material test results revealed that the enhanced photocatalytic performance of PS@rGO@MnO2 was due to the improvement of light utilization rate, the reduction of electron-hole pair recombination rate, and the improvement of charge separation efficiency and transfer efficiency. ECOSAR model predictions indicate that CFX can effectively reduce toxicity in photocatalytic reactions. The removal performance of actual natural water verified that the material was of great practical application potential.

Morphology and Environmental Applications of Bismuth Compound Nano-Photocatalytic Materials: A Review

Many great breakthroughs have been made in the past five years in understanding the mechanism of bismuth compounds. However, the actual efficiency achieved with this material to date is far away from the theoretical conversion efficiency. The structure and morphology have been proven to be vital factors to enhance the electronic migration to influence photocatalytic performance. Bismuth compounds with different structures and morphologies have certain application prospects in environmental governance due to their small band gap and strong visible light response. This review is aimed at summarizing the recent experimental and bandgap computational breakthroughs in photocatalytic properties of bismuth oxides and halides, in the meanwhile, compared with the band gap adjustment, the recombination of photoexcited electron–hole (e−–h+) pairs is one of the most important factors for the photocatalytic performance. Although bismuth compounds photocatalyst has been used for environmental applications, our understanding on the degradation mechanism of organic matters is limited. The target location and the degree of mineralization for different pollutants are not yet clear. Moreover, photocatalytic material needs to match the potential of the photogenerated e−–h+ pairs to the potential required to degrade the pollutant to be oxidized or reduced. We aim to provide guidelines for the rational design and fabrication of highly efficient bismuth compounds materials for water treatment. Additionally, the potential applications of bismuth compounds in environment are presented for future research directions.

Nano-Photocatalytic Materials: Possibilities and Challenges

Photocatalysis is one of the most promising processes within catalysis, due to its increasing potential and the possibility of its being combined with renewable solar energy [...]

Electrochemically Synthesized Nano-photocatalysts for Photodegradation of Organic Compounds

Over the last decades, extensive studies have been carried out on nano-photocatalytic materials finding a broad range of applications mainly in solar energy conversion and environmental remediation. This article focuses on synthesizing a novel nano-photocatalyst material for purifying water from chloro-organic pollutants and microbes. It was synthesized in the electrolytic cell with titanium and graphite electrodes. TEM analysis revealed that the obtained nanocarbon-titanium composite has a spherical morphology, the average dimension of nanoparticles is 6±2 nm. The electrochemically synthesized nano-photocatalyst forms OH radicals in the presence of water vapor during daylight hours under sunlight’s ultraviolet radiation. As soon as extremely reactive OH radicals are formed, they react with organic pollutants. The results of photodegradation of E. Coli, methyl orange, methyl blue, and polychlorinated biphenyls in the ultraviolet spectrum of sunlight have been discussed. The effect of pH value on the decolorization efficiency has been also observed. The obtained photodegradation time of methyl orange (MeO) and methyl blue (MeB) solutions was less than 60 minutes, and the destruction time of polychlorinated biphenyl (PCB) compounds was about 6-8 hours. The practical application of the developed nano-photocatalyst material promises to be an inexpensive, viable alternative or complimentary method for water and wastewater treatment at ambient temperature to degrade various chemical and microbiological pollutants in water.

ALUMINUM–α-HEMATITE THIN FILMS FOR PHOTOELECTROCHEMICAL APPLICATIONS

In recent years, photoelectrochemical (PEC) based devices have become attractive due to production of hydrogen by splitting water using photocatalyst alpha ([Formula: see text])-hematite (Fe2O3) as an electrode material due to its bandgap, low cost, chemical stability and extreme abundance in nature. The [Formula: see text]-Fe2O3 is also related to low carrier diffusion due to higher resistivity, slow surface kinetics, low electron mobility and higher electro–hole combination. The carrier mobility and carrier diffusion properties of [Formula: see text]-Fe2O3 have been enhanced by doping as well as composite formation. Keeping in view the enhanced properties of [Formula: see text]-Fe2O3, attempt is being made to dope and form composite using trivalent “aluminum” ions. The Al–[Formula: see text]-Fe2O3 nanophotocatalytic materials were synthesized by varying the ratio of Al to [Formula: see text]-Fe2O3 using sol–gel technique. The nanomaterials “[Formula: see text]-Fe2O3 and Al–[Formula: see text]-Fe2O3” were physically characterized through X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and UV–visible techniques, respectively. The diffusion coefficient of nanomaterials at the electrode/electrolyte interface was analyzed using electrochemical analysis. Interestingly, the presence of aluminum causes the [Formula: see text]-Fe2O3 to change the structural, optical and morphological properties of nanomaterials. The bandgaps of [Formula: see text]-Fe2O3 vary from 2.2[Formula: see text]eV to 2.45[Formula: see text]eV due to presence of aluminum in the structure. The photocurrent studied on Al–[Formula: see text]-Fe2O3 based electrode clearly shows the enhanced hydrogen production under photoelectrochemical cell.

The photocatalytic degradation of methylene blue by green semiconductor films that is induced by irradiation by a light-emitting diode and visible light

ABSTRACTThis study develops a low-energy rotating photocatalytic contactor (LE-RPC) that has Cu-doped TiO2 films coated on stainless-steel rotating disks, to experimentally evaluate the efficiency of the degradation and decolorization of methylene blue (MB) under irradiation from different light sources (visible 430 nm, light-emitting diode [LED] 460 nm, and LED 525 nm). The production of hydroxyl radicals is also examined. The experimental results show that the photocatalytic activity of TiO2 that is doped with Cu2+ is induced by illumination with visible light and an LED. More than 90% of methylene blue at a 10 mg/L concentration is degraded after illumination by visible light (430 nm) for 4 hr at 20 rpm. This study also demonstrates that the quantity of hydroxyl radicals produced is directly proportional to the light energy intensity. The greater the light energy intensity, the greater is the number of hydroxyl radicals produced.Implications: The CuO-doped anatase TiO2 powder was successfully synthesized in this study by a sol–gel method. The catalytic abilities of the stainless-steel film were enhanced in the visible light regions. This study has successfully modified the nano-photocatalytic materials to drop band gap and has also successfully fixed the nano-photocatalytic materials on a substratum to effectively treat dye wastewater in the range of visible light. The results can be useful to the development of a low-energy rotating photocatalytic contactor for decontamination purposes.

Preparation of Si doped molecularly imprinted TiO2 photocatalyst and its degradation to antibiotic wastewater

ABSTRACTTiO2, molecularly imprinted TiO2 (TiO2/OTC) and a novel Si doped molecularly imprinted TiO2 (TiO2/SiO2/OTC) nano photocatalytic materials were prepared by liquid phase deposition method. The products were characterized by XRD and SEM. The photocatalytic activities of the samples were evaluated by the photocatalytic degradation of oxytetracycline wastewater under a xenon lamp irradiation. The results showed that TiO2/SiO2/OTC and TiO2/OTC could improve both the photocatalytic activity and the molecular recognition ability, while the photocatalytic activities of TiO2/SiO2/OTC sample was more effective than TiO2/OTC sample with 5 times reuse. The photocatalytic activity of TiO2/SiO2/OTC photocatalyst sample had a greater improvement and its photocatalytic degradation of oxytetracycline wastewater reached 80.79% in 120 minute reaction.

“Green” colloidal ZnS quantum dots/chitosan nano-photocatalysts for advanced oxidation processes: Study of the photodegradation of organic dye pollutants

Quantum dots (QDs) are semiconductor nanoparticles that are emerging as a new class of fluorescent nanomaterials for environmental applications. Heterogeneous photocatalysis using QDs is an attractive technology for the advanced treatment of water contaminated with organic dyes. In this work, novel nano-photocatalysts based on ZnS QDs functionalized with chitosan were developed using a “green” colloidal chemical method in aqueous media at room temperature. These ZnS/chitosan nano-photocatalysts (ZnS–CHI) were extensively characterized, and the results demonstrated that chitosan was an effective capping ligand for the direct production of water-soluble ZnS QDs with an average nanocrystal size of 3.8nm. Methylene blue and methyl orange dyes, which were used as model organic pollutants, were effectively oxidized by the photocatalytic activity of the ZnS/chitosan nanostructured systems under UV irradiation. In addition, the ZnS–CHI nano-conjugates exhibited blue photoluminescent behavior upon ultraviolet excitation. Therefore, a “green” facile chemical synthesis of fluorescent nano-photocatalytic materials was developed using an abundant biocompatible polysaccharide that exhibit potential for the photodegradation of hazardous organic pollutants present in wastewater and several other environmentally friendly applications.

Process Optimization and Application of Supported Nano-Photocatalytic Materials

Melt Phase-splitting[1] method was a new one of preparing supported nano-photocatalytic materials.The nano TiO2 prepared loaded to the porous glass carrier. In this study,the technology of preparing nano TiO2 by melt phase-splitting method was Optimization, also doing doping modifcation on them. Using nano TiO2 photocatalyst to do photocatalytic degradation test on formaldehyde.The result had shown that: the degradation efficiency of the catalyst containing ZnO was higher than that free of ZnO. The rate of degradation of formaldehyde of the catalyst free of ZnO could reached 58.7% in 8 hours, but that of the catalyst containing was only 53.3%. Using fluorescent lamps as the light source,the photocatalytic efficiency of the catalyst free of ZnO could reached 43.2%.