Photocatalytic degradation of phenol in natural seawater using visible light active carbon modified (CM)-n-TiO2 nanoparticles under UV light and natural sunlight illuminations

Nanostructured Metal Oxide-Based Electrochemical Biosensors in Medical Diagnosis

Nanostructured metal oxides (NMOs) provide electrical properties such as high surface-to-volume ratio, reaction activity, and good adsorption strength. Furthermore, they serve as a conductive substrate for the immobilization of biomolecules, exhibiting notable biological activity. Capitalizing on these characteristics, they find utility in the development of various electrochemical biosensing devices, elevating the sensitivity and selectivity of such diagnostic platforms. In this review, different types of NMOs, including zinc oxide (ZnO), titanium dioxide (TiO2), iron (II, III) oxide (Fe3O4), nickel oxide (NiO), and copper oxide (CuO); their synthesis methods; and how they can be integrated into biosensors used for medical diagnosis are examined. It also includes a detailed table for the last 10 years covering the morphologies, analysis techniques, analytes, and analytical performances of electrochemical biosensors developed for medical diagnosis.

Development of a Solid Catalyst Based on Pt Supported on Heterostructure (NaNbO3/NaNb3O8/NiO) Applied to the Photodegradation of Phenol in Seawater

Phenol and its derivatives are present in effluents from several industrial processes, such as petroleum refining (produced water) and the pharmaceutical industry, and they are highly toxic. The present work elaborated a new catalyst for the removal of phenol and its derivatives. The photocatalyst was prepared by a simple method from the ammonium oxalate of niobium and nickel nitrate, resulting in heterostructures (principally NaNbO3/NaNb3O8 and a lesser amount of NiO) named NiNb. Platinum was deposited on this catalyst (NiNb/Pt catalyst), and its photocatalytic activity was tested on the degradation of phenol in seawater and distilled water, in the presence and absence of UV-C light (germicidal, λ = 254 nm), and with varying concentrations of platinum and varying pH of the solution. The catalyst was characterized by different techniques (SEM, EDS, DRS, XRD, TXRF, SBET,). The results of the study showed that the NiNb/Pt catalyst achieved 65% phenol removal in seawater and about 57% removal in distilled water. The reuse of the catalyst was also studied, and the photocatalytic mechanism was investigated by tests with scavenger agents and terephthalic acid.

Sunlight-mediated photocatalytic removal of phenanthrene from wastewater using carbon-doped zinc oxide (C-ZnO) nanoparticles

In an effort for efficient solar energy harvesting, carbon-doped zinc oxide (C-ZnO) nanoparticles with intriguing properties were synthesized by sonicated sol-gel technique with the aid of activated charcoal. Compared to pure ZnO, the incorporation of carbon has drastically promoted the photocatalytic activity of C-ZnO towards the degradation of phenanthrene under illumination of both UV and sunlight. The characterization of the as-synthesized nanoparticles by scanning electron microscope (SEM), UV-vis spectra, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS) confirmed the carbon doping of C-ZnO. The highest degradation rate of phenanthrene was obtained at pH 7 and C-ZnO loading of 0.5 g L^-1. Finally, the kinetic studies of the photocatalytic degradation of phenanthrene by using C-ZnO were well-fitted with the Langmuir-Hinshelwood model and followed the pseudo-first-order rate expression.

Photocatalytic degradation of 2,4-DNT in simulated wastewater by magnetic CoFe2O4/SiO2/TiO2 nanoparticles

Discharge of 2,4-dinitrotoluene (2,4-DNT) into the environment leads to a serious soil and water sources pollution problem, due to toxicity and possible carcinogenicity of this toxic substance. In this work, the photocatalytic degradation of 2,4-DNT was investigated using CoFe₂O₄/SiO₂/TiO₂ nanoparticles. The catalyst features were characterized by using XRD, TEM, EDX, UV-vis DRS, FTIR, and VSM techniques. The influence of different experimental factors on degradation efficiency including pH value, catalyst dosages, and initiate concentration of 2,4-DNT were investigated. Mineralization of the model pollutant was determined using TOC analysis under optimum conditions. A possible mechanism, process kinetic and reusability of magnetic photocatalyst were also performed. In optimum experimental conditions (pH=3, photocatalyst dosage=0.75 g/L, 2,4-DNT=0.025 g/L), degradation efficiency achieved 88.5% within 180-min reaction time with TOC removal of 55.6%. Dominate oxidizing radicals during the degradation of 2,4-DNT by CoFe₂O₄/SiO₂/TiO₂ were hydroxyl radicals. The photocatalytic degradation of 2,4-DNT followed first-order rate kinetics. After three successive use cycles, the degradation efficiency was reduced by 64%. Our results revealed that the synthesized CoFe₂O₄/SiO₂/TiO₂ photocatalyst was a good choice for degradation of 2,4-DNT, due to proper potential reusability and catalytic activity.

Enhanced photocatalytic activity of two dimensional ternary nanocomposites of ZnO-Bi2WO6-Ti3C2 MXene under natural sunlight irradiation

The design and development of advanced photocatalysts for water purification have attracted much attention from researchers in recent years. In this context, the two-dimensional (2D) semiconducting materials have shown excellent photocatalytic properties due to their merits of high surface area, confined longitudinal dimensions and excellent capability of efficient separation and transfer of photogenerated charge carriers. Herein, we report a novel 2D-2D-2D ternary photocatalyst ZnO-Bi₂WO₆-Ti₃C₂ by using a two-step electrostatic assembly route. The formation of the individual materials and nanocomposites was confirmed by x-ray diffraction and 2D morphology was ascertained by electron microscopy studies. The as-prepared photocatalysts were utilized for the degradation of a colorless pharmaceutical pollutant, ciprofloxacin (CFX) under natural sunlight irradiation. It was found that the optimized ternary photocatalyst showed a maximum degradation (∼77%) of CFX in 160 min. The mechanistic investigation showed that upon nanocomposite formation, the electrons flow from ZnO and Bi₂WO₆ to Ti₃C₂, implying that MXene plays an important role in the separation of photogenerated charges and thereby enhancing the photocatalytic activity. This work paves the way for the design and development of efficient photocatalysts for environmental remediation.

Ultraviolet light accelerates the degradation of polyethylene plastics

Polyethylene plastics are widely used in daily life in the packaging of foodstuffs, pharmaceuticals, cosmetics, detergents, and chemicals. In this study, low-density polyethylene (LDPE) was exposed to an ultraviolet (UV) fluorescence lamp in simulated aging and degradation experiments. Ultraviolet degradation mechanisms were investigated on the surface after sunlight and UV lamp exposure. The plastic surfaces' molecular and surface degradation results were compared with their Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) and ultraviolet visible (UV-Vis) spectra. By growing the length of exposure time increased stages of degradation were observed. After UV lamp and sunlight exposure, changing degradation levels were also determined with spectroscopic evaluations and the results were compared. LDPE was selected since it has a simple structure and a number of branched polymer structures that facilitate easily disruption of the chemical bond. Breaks in the polymer chain were easily seen in the plastics at the end of degradation and a fragile structure was formed throughout the polymer chain after accelerating UV light aging. The FTIR spectrum clarified the changed and fractured molecular bond structures of UV-exposed polyethylene. The change in the molecular structure of the plastic caused small changes in its color and small variations in this color change were detected by recording the Ultraviolet-Visible (UV-Vis) spectrum. The Philips UV lamp's light intensity and the wavelength spectrum range were measured. The UV lamp and sun UV light doses were calculated and compared.

Preparation and characterization of titanium dioxide nanoparticles and in vitro investigation of their cytotoxicity and antibacterial activity against Staphylococcus aureus and Escherichia coli

Titanium dioxide nanoparticles (TiO₂ NPs) are photo-active metallic nanoparticles becoming promising agents in modern biomedical applications. Herein, a novel process for the synthesis of TiO₂ NPs with high stability was developed by a sol-gel process and to investigate their cytotoxicity and antibacterial activity. Numerous experiments have been performed to confirm the morphologies, compositions, and physicochemical properties of prepared TiO₂ NPs, such as field emission scanning electron microscopy, dynamic light scattering, Zeta potential, Fourier transform infrared spectroscopy and X-ray diffraction. MTT assay was applied to assess the cytotoxicity of the prepared nanoparticles. The results indicate that the synthesized nanoparticles' diameter is about 68 nm and contains the anatase phase, in the range of 2θ from 25 to 80 °C. The hydrodynamic radius of nanoparticles is about 140.4 nm, and the zeta potential of nanoparticles is about -44.6 mV. The MTT results have not shown any toxicity; the antibacterial inhibitory effect of TiO₂ NPs at 200 mg/mL concentrations exhibited superior antibacterial activity at 15.9 ± 0.1, 14.0 ± 0.1 against Staphylococcus aureus and Escherichia coli, respectively. In conclusion, colloidal solutions with high stability were successfully synthesized, contributing to decreased dimensions and increased antibacterial properties.

Degradation of Acetaminophen via UVA-induced advanced oxidation processes (AOPs). Involvement of different radical species: HO, SO4- and HO2/O2. CHEMOSPHERE 2020;258:127268. [PMID: 32569955 DOI: 10.1016/j.chemosphere.2020.127268]

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO₄^- and HO₂/O₂^-) are generated through activation of hydrogen peroxide (H₂O₂), sodium persulfate (Na₂S₂O₈) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/H₂O₂ and UVA/Na₂S₂O₈ systems whatever the solution's pH. To explain these results, second order reaction rate constant (k_{radical, ACTP}) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO₂/O₂^- radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and Na₂S₂O₈ exhibits synergistic effects rather than antagonism effects with H₂O₂. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

Photochemical activation routes are gaining the attention of the scientific community since they can offer an alternative to the traditional chemical industry that mainly utilizes thermochemical activation of molecules. Photoreactions are fast and selective, which would potentially reduce the downstream costs significantly if the process is optimized properly. With the transition towards green chemistry, the traditional batch photoreactor operation is becoming abundant in this field. Process intensification efforts led to micro- and mesostructured flow photoreactors. In this work, we are reviewing structured photoreactors by elaborating on the bottleneck of this field: the development of an efficient scale-up strategy. In line with this, micro- and mesostructured bench-scale photoreactors were evaluated based on a new benchmark called photochemical space time yield (mol·day⁻¹·kW⁻¹), which takes into account the energy efficiency of the photoreactors. It was manifested that along with the selection of the photoreactor dimensions and an appropriate light source, optimization of the process conditions, such as the residence time and the concentration of the photoactive molecule is also crucial for an efficient photoreactor operation. In this paper, we are aiming to give a comprehensive understanding for scale-up strategies by benchmarking selected photoreactors and by discussing transport phenomena in several other photoreactors.

Recent advances in the removal of persistent organic pollutants (POPs) using multifunctional materials:a review

Persistent organic pollutants (POPs) have gained heightened attentions in recent years owing to their persistent property and hazard influence on wild life and human beings. Removal of POPs using varieties of multifunctional materials have shown a promising prospect compared with conventional treatments. Herein, three main categories, including thermal degradation, electrochemical remediation, as well as photocatalytic degradation with the use of diverse catalytic materials, especially the recently developed prominent ones were comprehensively reviewed. Kinetic analysis and underlying mechanism for various POPs degradation processes were addressed in detail. The review also systematically documented how catalytic performance was dramatically affected by the nature of the material itself, the structure of target pollutants, reaction conditions and treatment techniques. Moreover, the future challenges and prospects of POPs degradation by means of multiple multifunctional materials were outlined accordingly. Knowing this is of immense significance to enhance our understanding of POPs remediation procedures and promote the development of novel multifunctional materials.

Synthesis and Photocatalytic Sterilization Performance of SA/TiO2

The photocatalyst sorbic acid (SA)/titanium dioxide (TiO₂) was successfully synthesized by sol–gel method and characterized. The composite exhibited regularly spherical particles with the size of 50 nm and the specific surface area of 90.3 m² g⁻¹, furthermore, it showed mesoporous structure and significantly improved dispersion. SA was grafted on TiO₂ surface by –COOTi and TiO₂ existed as pure anatase phase in the composite. The addition of SA made the band gap of TiO₂ increased from 3.03 to 3.35 eV, which indicting that the composite exhibited a strong response to the ultraviolet light. The optimum preparation parameters of the catalyst were as follows: n(Ti):n(SA) = 1:0.05, ethanol 60 mL, glacial acetic acid 40 mL, hydrothermal temperature 180 °C, hydrothermal time 12 h. The composite could reach the 4.31 log reduction of E. coli, with the optimum catalyst dosage of 0.7 g L⁻¹, irradiated by UV light for 60 min. SA/TiO₂ was an environmentally friendly, non-toxic and safe sterilized nanocomposite material appropriate for future bactericidal applications, providing a new way to effectively increase the dispersion of TiO₂ particles to achieve superior photocatalytic sterilization efficiency.

A new Rhodococcus aetherivorans strain isolated from lubricant-contaminated soil as a prospective phenol-biodegrading agent

Microbe-based decontamination of phenol-polluted environments has significant advantages over physical and chemical approaches by being relatively cheaper and ensuring complete phenol degradation. There is a need to search for commercially prospective bacterial strains that are resistant to phenol and other co-pollutants, e.g. oil hydrocarbons, in contaminated environments, and able to carry out efficient phenol biodegradation at a variable range of concentrations. This research characterizes the phenol-biodegrading ability of a new actinobacteria strain isolated from a lubricant-contaminated soil environment. Phenotypic and phylogenetic analyses showed that the novel strain UCM Ac-603 belonged to the species Rhodococcus aetherivorans, and phenol degrading ability was quantitatively characterized for the first time. R. aetherivorans UCM Ac-603 tolerated and assimilated phenol (100% of supplied concentration) and various hydrocarbons (56.2–94.4%) as sole carbon sources. Additional nutrient supplementation was not required for degradation and this organism could grow at a phenol concentration of 500 mg L⁻¹ without inhibition. Complete phenol assimilation occurred after 4 days at an initial concentration of 1750 mg L⁻¹ for freely-suspended cells and at 2000 mg L⁻¹ for vermiculite-immobilized cells: 99.9% assimilation of phenol was possible from a total concentration of 3000 mg L⁻¹ supplied at daily fractional phenol additions of 750 mg L⁻¹ over 4 days. In terms of phenol degradation rates, R. aetherivorans UCM Ac-602 showed efficient phenol degradation over a wide range of initial concentrations with the rates (e.g. 35.7 mg L⁻¹ h⁻¹ at 500 mg L⁻¹ phenol, and 18.2 mg L⁻¹ h⁻¹ at 1750 mg L⁻¹ phenol) significantly exceeding (1.2–5 times) reported data for almost all other phenol-assimilating bacteria. Such efficient phenol degradation ability compared to currently known strains and other beneficial characteristics of R. aetherivorans UCM Ac-602 suggest it is a promising candidate for bioremediation of phenol-contaminated environments.

Investigation of photocatalytic behavior of modified ZnS:Mn/MWCNTs nanocomposite for organic pollutants effective photodegradation

In this research, zinc sulfide (ZnS) doped with manganese (Mn) is synthesized on functionalized multiwall carbon nanotubes (MWCNTs) nanocomposite by a facile co-precipitation method as the photocatalysis. Due to the excellent electrical and optical characteristics of ZnS:Mn/MWCNTs nanocomposite, it is worth to investigate its photodegradation activity. To investigate the photocatalytic degradation properties of organic pollutants, the synthesis conditions were optimized in the presence of four substances: COOH, ethylene glycol, sodium dodecyl sulfate, and polyvinyl-pyrrolidone. Surface studies of the photocatalyst, i.e., structural, morphological, optical and physical properties, were characterized by FTIR, PL, XRD, SEM, and TEM analyses. The results showed that Mn ions decreased the band gap energy of the nanocomposites and there was excellent adhesion between ZnS and MWCNTs in the synthesized composite. According to the results, MWCNTs effectively increased the photocatalytic activity of the ZnS nanoparticles by the electron-hole pair recombination of ZnS and MWCNTs, and the composites with the carboxylic functional group showed greater photocatalytic activity. In addition, the kinetic studies showed that the photocatalytic process obeyed the pseudo-first-order kinetic model. To determine the exact mathematical formula of the photocatalysis, response surface methodology was modeled by the central composite design method. Various parameters, such as the time of the treatment process and initial concentration of the pollutants were studied for a quadratic model that fit all the cases well and their mathematical models were obtained.

Production of Methanol as a Fuel Energy from CO2 Present in Polluted Seawater - A Photocatalytic Outlook

The production of methanol by photocatalytic reduction of the CO2present in the different polluted seawater systems was explored using P–25, C/TiO2, and Cu-C/TiO2under both UV and sunlight. Both C/TiO2and Cu-C/TiO2were synthesized by the sonicated sol-gel method. The prepared photocatalyst demonstrated maximum efficiency when the dosage of photocatalysts was 1g/L and the doping level was 3wt% of copper. The maximum methanol yields of two observed polluted seawater systems were 2910 μmol/g and 2250 μmol/g after 5 hour illumination of UV light. However, the 5 hour natural sunlight illumination generated the yield of 990 μmol/g and 910 μmol/g of methanol. The observed results demonstrated that band gap narrowing of the photocatalyst by carbon modification and the restriction of electron-hole pair combination by copper doping both greatly enhanced the photocatalytic reduction of CO2to methanol under both UV and natural sunlight.

Low Temperature Synthesis of Large-Size Anatase TiO2 Nanosheets with Enhanced Photocatalytic Activities

TiO₂ nanosheets have continuously been intriguing due to their high surface activities as photocatalyst but still challenging to synthesis large-scale 2D nanostructures. A special microstructure evolution of TiO₂ , ripening in aqueous solution at low temperature (≈4 °C), is found for the first time, i.e., from the initial aperiodic atom-networks gradually into low crystallized continuous spongy structure with small crystal facets and ultimately forming large-size anatase nanosheets with exposed (101) and (200) facets. Based on this finding, the synthesized anatase TiO₂ nanosheets possess monodispersed large-scale 2D nanostructure so as to exhibit appreciable quantum size effects and remarkable enhanced optical absorption capacity. Using photocatalytic reduction of Cr (VI) to Cr (III) as the probe reaction to evaluate photocatalytic activities of the TiO₂ nanosheets, the reductivity of Cr (VI) achieves 99.8% in 15 min under irradiation of 200-800 nm light. At the same time, an in situ Cr (III)-doping occurs spontaneously and triggers pronounced visible light driven photocatalysis, reducing 99% of Cr (VI) in 100 min under irradiation of 400-800 nm light.

Three-way spectrofluorimetric-assisted multivariate determination of nonylphenol ethoxylate and 2-naphtalene sulfonate in wastewater samples and optimization approach for their photocatalytic degradation by CoTiO3 nanostructure

This study presents a new strategy for the simultaneous quantification of two industrial contaminants. The excitation-emission fluorescence data matrix combined with a three-way chemometric method, such as parallel factor analysis, was used for the determination of nonylphenol ethoxylate (NPE-9) as a nonionic surfactant and 2-naphthalene sulfonate (2-NS) in waste water samples. It is noticeable that this method can resolve overlapping signal into spectral and relative concentration profiles. By spiking the known concentrations of these compounds in the wastewater samples, the accuracy of the proposed methods was validated and recoveries of the spiked values were calculated. High recoveries (i.e. 90-110%) obtained for the waste water samples indicate the present method can be used successfully to determine the analytes concentration in the environmental contaminations. The photocatalytic degradation of NPE-9 and 2-NS in aqueous solution was studied using the CoTiO₃ nanoparticles catalyst. It was synthesized by the sol-gel technique. The catalytic activity of the prepared nanoparticles was measured in a batch photoreactor containing appropriate solutions of these compounds with UV irradiation. The photodegradation process of these compounds was optimized by using the central composite design. The CoTiO₃ showed high activity for UV-photocatalytic degradation of NPE-9 and 2-NS.

Emerging trends in photodegradation of petrochemical wastes: a review

Various human activities like mining and extraction of mineral oils have been used for the modernization of society and well-beings. However, the by-products such as petrochemical wastes generated from such industries are carcinogenic and toxic, which had increased environmental pollution and risks to human health several folds. Various methods such as physical, chemical and biological methods have been used to degrade these pollutants from wastewater. Advance oxidation processes (AOPs) are evolving techniques for efficient sequestration of chemically stable and less biodegradable organic pollutants. In the present review, photocatalytic degradation of petrochemical wastes containing monoaromatic and poly-aromatic hydrocarbons has been studied using various heterogeneous photocatalysts (such as TiO₂, ZnO and CdS. The present article seeks to offer a scientific and technical overview of the current trend in the use of the photocatalyst for remediation and degradation of petrochemical waste depending upon the recent advances in photodegradation of petrochemical research using bibliometric analysis. We further outlined the effect of various heterogeneous catalysts and their ecotoxicity, various degradation pathways of petrochemical wastes, the key regulatory parameters and the reactors used. A critical analysis of the available literature revealed that TiO₂ is widely reported in the degradation processes along with other semiconductors/nanomaterials in visible and UV light irradiation. Further, various degradation studies have been carried out at laboratory scale in the presence of UV light. However, further elaborative research is needed for successful application of the laboratory scale techniques to pilot-scale operation and to develop environmental friendly catalysts which support the sustainable treatment technology with the "zero concept" of industrial wastewater. Nevertheless, there is a need to develop more effective methods which consume less energy and are more efficient in pilot scale for the demineralization of pollutant.

Electrospinning Directly Synthesized Porous TiO2 Nanofibers Modified by Graphitic Carbon Nitride Sheets for Enhanced Photocatalytic Degradation Activity under Solar Light Irradiation

We report a direct approach to the fabrication of a composite made of porous TiO2 nanofibers (NFs) and graphitic carbon nitride (g-C3N4) sheets, by means of an angled two-nozzle electrospinning combined with calcination process. Different wt % amounts of g-C3N4 particles in a polymer solution from one nozzle and TiO2 precursors containing the same polymer solution from another nozzle were electrospun and deposited on the collector. Structural characterizations confirm a well-defined morphology of the TiO2/g-C3N4 composite in which the TiO2 NFs are uniformly attached on the g-C3N4 sheet. This proper attachment of TiO2 NFs on the g-C3N4 sheets occurred during calcination. The prepared composites showed the enhanced photocatalytic activity over the photodegradation of rhodamine B and reactive black 5 under natural sunlight. Here, the synergistic effect between the g-C3N4 sheets and the TiO2 NFs having anisotropic properties enhanced the photogenerated electron-hole pair separation and migration, which was confirmed by the measurement of photoluminescence spectra, cyclic voltammograms, and electrochemical impedance spectra. The direct synthesis approach that is established here for such kinds of sheetlike structure and porous NFs composites could provide new insights for the design of high-performance energy conversion catalysts.

Enhanced degradation of phenol by Sphingomonas sp. GY2B with resistance towards suboptimal environment through adsorption on kaolinite

The effects of clay minerals on microbial degradation of phenol under unfavorable environmental conditions were investigated. Degradation of phenol by Sphingomonas sp. GY2B adsorbed on kaolinite, montmorillonite, and vermiculite were evaluated in comparison with free bacteria under optimal conditions. Kaolinite was found to be the most effective in accelerating degradation rate (reducing the degradation time) as well as improving degradation efficiency (increasing the percentage of phenol degraded), with GY2B/kaolinite complex achieving a degradation efficiency of 96% within 6 h. GY2B adsorbed on kaolinite was more competent than free GY2B in degradation under conditions with high phenol concentrations and at alkaline pH. Kaolinite reduced the time required for degradation by 8-12 h and improved the degradation efficiency by as much as 82% at high phenol concentrations. Meanwhile, the GY2B/kaolinite complex reduced the degradation time by 24 h and improved the degradation efficiency by 46% at pH 12. The improvement was partially due to the buffering effects of kaolinite. It was also shown that Cr(VI) and kaolinite synergistically enhanced the degradation by GY2B, with Cr(VI) and kaolinite both increasing the degradation rate and kaolinite being primarily responsible for enhanced degradation efficiency. These results showed one of the common clay minerals, kaolinite, is able to significantly improve the microbial degradation performance, and protect microorganisms against unfavorable environment. Kaolinite can collaborate with Cr(VI) to further improve the microbial degradation performance. It is implied that clay minerals have great potential to be applied in enhancing the biodegradation of phenol.

Improved WO3 photocatalytic efficiency using ZrO2 and Ru for the degradation of carbofuran and ampicillin

The photocatalytic degradation of carbofuran (pesticide) and ampicillin (pharmaceutical) using synthesized WO3/ZrO2 nanoparticles under simulated solar light was investigated. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectra analyses were used to characterize the prepared catalysts. The optimum ratio of WO3 to ZrO2 was determined to be 1:1 for the degradation of both contaminants. The degradation of carbofuran and ampicillin by WO3/ZrO2 after 240 min of irradiation was 100% and 96%, respectively. Ruthenium (Ru) was employed as an additive to WO3/ZrO2 to enhance the photocatalytic degradation rate. Ru/WO3/ZrO2 exhibited faster degradation rates than WO3/ZrO2. Furthermore, 100% and 97% degradation of carbofuran and ampicillin, respectively, was achieved using Ru/WO3/ZrO2 after 180 min of irradiation. The durability of the catalyst was investigated by reusing the same suspended catalyst, which achieved 92% of its initial efficiency. The photocatalytic degradation of ampicillin and carbofuran followed pseudo-first order kinetics according to the Langmuir-Hinshelwood model.

Prospective aspects of preferential {001} facets of N,S-co-doped TiO2 photocatalysts for visible-light-responsive photocatalytic activity

In this report, we describe the synthesis of nitrogen and sulfur co-doped TiO₂ photocatalysts (NST) with preferential {001} facets by surfactant- and template-free OPM routes and crystallized through hydrothermal treatment.

Rapid and morphology controlled synthesis of anionic S-doped TiO2 photocatalysts for the visible-light-driven photodegradation of organic pollutants

In recent years, growing concerned has been raised to the global problem of the drainage of organic pollutants into water steams.

Microwave-assisted synthesis of BiFeO3 nanoparticles with high catalytic performance in microwave-enhanced Fenton-like process

Synthesis of BiFeO₃ using microwave-assisted hydrothermal synthesis method.

Synthesis, characterization and application of ZnO-Ag as a nanophotocatalyst for organic compounds degradation, mechanism and economic study

The current work deals with ZnO-Ag nanocomposites (in the wide range of x in the Zn1-xO-Agx chemical composition) synthesized using microwave assisted solution combustion method. The structural, morphological and optical properties of the samples were characterized by XRD (X-ray diffraction), FTIR (Fourier transform infrared spectrometry), SEM (scanning electron microscopy technique), EDX (energy dispersive X-ray spectrum), ICP (inductively coupled plasma technique), TEM (transmission electron microscopy), BET (Brunauer-Emmett-Teller method), UV-Vis (ultraviolet-visible spectrophotometer) and photoluminescence spectrophotometer. The photocatalytic activity of the ZnO-Ag was investigated by photo-degradation of Acid Blue 113 (AB 113) under UV illumination in a semi-batch reactor. This experiment showed that ZnO-Ag has much more excellent photocatalytic properties than ZnO synthesized by the same method. The enhanced photocatalytic activity was due to the decrease in recombination of photogenerated electron-holes. The results showed the improvement of ZnO photocatalytic activity and there is an optimum amount of Ag (3.5mol%) that needs to be doped with ZnO. The effect of operating parameters such as pH, catalyst dose and dye concentration were investigated. The reaction byproducts were identified by LC/MS (liquid chromatography/mass spectrometry) analysis and a pathway was proposed as well. Kinetic studies indicated that the decolorization process follows the first order kinetics. Also, the degradation percentage of AB 113 was determined using a total organic carbon (TOC) analyzer. Additionally, cost analysis of the process, the mechanism and the role of Ag were discussed.

Fe₃O₄/SiO₂/TiO₂ nanoparticles for photocatalytic degradation of 2-chlorophenol in simulated wastewater

Photocatalysis has emerged as an advance and environmental-friendly process for breakdown of organic contaminants in wastewater. This work reports facile synthesis and characterization of stable magnetic core-shell-shell Fe3O4/SiO2/TiO2 nanoparticles and their effectiveness for photocatalysis. The surface morphology, crystal structure, and chemical properties of the photocatalyst were characterized by using scanning electron microscope (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and nitrogen physisorption. Stability of synthesized nanoparticles in aqueous medium was tested by leaching test. The photocatalytic degradation of 2-chlorophenol was investigated and reaction parameters for best catalyst performance were optimized. Catalyst dose of 0.5 g/L under optimized conditions produced complete degradation of 25 mg/L 2-chlorophenol (2-CP) within 130 min of 100-W ultraviolet (UV) irradiation while 97.2 % degradation of 50 mg/L 2-CP was achieved within 3 h. The rate of photocatalytic degradation was determined by considering pseudo first-order kinetics and Hugul's kinetic equations. The Hugul's kinetics was found to provide a better interpretation of the experimental results than the generally adopted pseudo first-order reaction kinetics.

The comparative photodegradation activities of pentachlorophenol (PCP) and polychlorinated biphenyls (PCBs) using UV alone and TiO2-derived photocatalysts in methanol soil washing solution

Photochemical treatment is increasingly being applied to remedy environmental problems. TiO₂-derived catalysts are efficiently and widely used in photodegradation applications. The efficiency of various photochemical treatments, namely, the use of UV irradiation without catalyst or with TiO₂/graphene-TiO₂ photodegradation methods was determined by comparing the photodegadation of two main types of hydrophobic chlorinated aromatic pollutants, namely, pentachlorophenol (PCP) and polychlorinated biphenyls (PCBs). Results show that photodegradation in methanol solution under pure UV irradiation was more efficient than that with either one of the catalysts tested, contrary to previous results in which photodegradation rates were enhanced using TiO₂-derived catalysts. The effects of various factors, such as UV light illumination, addition of methanol to the solution, catalyst dosage, and the pH of the reaction mixture, were examined. The degradation pathway was deduced. The photochemical treatment in methanol soil washing solution did not benefit from the use of the catalysts tested. Pure UV irradiation was sufficient for the dechlorination and degradation of the PCP and PCBs.

Synthesis of Titanium Containing SBA-15 and Its Application for Photocatalytic Degradation of Phenol

We synthesized Ti-containing SBA-15 by one-pot hydrothermal method and extensively investigated its physicochemical properties and examined its photocatalytic activity to degrade phenol. It’s shown that appropriate amount of titanium could be effectively incorporated into the framework of SBA-15 without provoking structure change and the tetrahedrally coordinated titanium species were well-ordered in Ti-incorporated SBA-15. Under UV-irradiation, the Ti-containing SBA-15 exhibits good photocatalytic activity for phenol degradation in the simulated waste water. The higher photocatalytic activity of Ti-containing SBA-15 to degrade phenol was ascribed to the more titanium content and anatase titanium dioxide. In addition, the new photocatalyst displays a good regeneration and cyclic performance after six runs.

Degradation of aqueous Rhodamine B by plasma generated along the water surface and its enhancement using nanocrystalline Fe-, Mn-, and Ce-doped TiO₂ films

The degradation of aqueous Rhodamine B (RhB) was examined using a dual-channel spark switch module designed to regulate the steepness of pulsed high voltage with microsecond rise time. Depending on the energy per pulse, a spark along the water surface (SPWS) or streamer along the water surface (STWS) was formed. STWS was found to have a better degradation effect and energy efficiency toward RhB than SPWS at the same power; however, addition of H₂O₂ amounts resulted in increased degradation, the effect being more pronounced using SPWS. The initial concentration of RhB also appeared to influence the rate constant of the degradation reaction. Furthermore, TiO₂ films doped with Fe, Mn, and Ce were found to enhance the degradation performance of plasma. A possible reaction mechanism of plasma formation along the water surface was concluded by determination of the main inorganic products in the liquid and gas phases.