Solar Light Irradiation Research Articles

Mg–Fe Layered Double Hydroxides/Polyacrylonitrile Nanofibers for Solar-Light Induced Peroxymonosulfate Elimination of Tetracycline Hydrochloride

The photo-induced peroxymonosulfate (photo-PMS) reaction is a promising route to eliminate antibiotics from waste water. To achieve excellent photo-PMS activity in Mg–Fe layered double hydroxides (LDHs) for tetracycline hydrochloride (TCH) degradation under simulative solar-light irradiation, Mg–Fe LDHs-loaded polyacrylonitrile (Mg–Fe/PAN) nanofibers were in-situ prepared via the hydrothermal route. For comparison to the photocatalysis and photo-PMS process, the Mg–Fe/PAN-assisted photo-PMS process exhibited a better elimination activity for TCH elimination. In addition, the photo-PMS activities of Mg–Fe/PAN composites were greatly affected by Mg–Fe LDHs content, TCH concentration, pH, and inorganic salts. Among these Mg–Fe/PAN composites, the optimal MgFe2/PAN with a Mg/Fe molar ratio of 1:2 and a nominal Mg–Fe LDHs content of 2.0 wt. % removed 81.31% TCH solution of 80 mg L−1 TCH within 120 min. This enhanced photo-PMS capacity of MgFe2/PAN was ascribed to the abundant active sites formed by functional groups and oxygen defects for efficient TCH species adsorption and photon capturing, and the tight interface between Mg–Fe LDHs nanoparticles and PAN nanofibers for the rapid separation and transfer of photoinduced e−/h+ pairs. SO4•− and •O2− radicals were vital for the MgFe2/PAN-assisted photo-PMS reaction.

NiO/MnFe2O4 Nanocomposite Photoluminescence, Structural, Morphological, Magnetic, and Optical Properties: Photocatalytic Removal of Cresol Red under Visible Light Irradiation.

In this study, pure nickel oxide (NiO), manganese ferrite (MnFe2O4 or MFO), and binary nickel oxide/manganese ferrite (NiO/MFO1-4) nanocomposites (NCs) were synthesized using the Sol-Gel method. A comprehensive investigation into their photoluminescence, structural, morphological, magnetic, optical, and photocatalytic properties was conducted. Raman analysis, UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction techniques were used to characterize the materials. The synthesized samples exhibited superparamagnetic behavior, as revealed by our analysis of their magnetic properties. A lower recombination rate was shown by the photoluminescence analysis, which is helpful for raising photocatalytic activity. The photocatalytic activity was evaluated for the degradation of Cresol Red (CR) dye. 91.6% of CR dye was degraded by NiO/MFO-4 nanocomposite, and the NC dosage as well as solution pH affected the photocatalytic performance significantly. In four sequential photocatalytic cycles, the magnetically separable NCs were stable and recyclable. The enhanced photocatalytic activity and magnetic separability revealed the potential application of NiO/MFO-4 as an efficient photocatalyst for the removal of dyes from industrial wastewater under solar light irradiation.

In-situ construct CuInS2/Bi/Bi2MoO6 S-scheme/Schottky dual heterojunctions catalyst for enhanced photocatalytic degradation of diclofenac sodium

In this paper, the S-scheme/Schottky heterojunction photocatalyst (CuInS2/Bi/Bi2MoO6, CIS/Bi/BMO) was successfully constructed via a facile in-situ solvothermal method, aimed at enhancing its photocatalytic performance. The results of the study on the photocatalytic degradation of diclofenac sodium (DCF) under simulated solar light irradiation revealed that the as-prepared composite exhibited remarkable catalytic efficiency in comparison to the pristine Bi2MoO6 and CuInS2. The plasmonic bismuth (Bi) was formed during the solvothermal process. Subsequently, CuInS2 and Bi were grown on the surface of Bi2MoO6 leading to forming CIS/BMO S-scheme heterojunction, along with a Schottky junction between Bi and Bi2MoO6. The use of ethylene glycol as a support was the main reason for the significant improvement in photocatalytic efficiency in the degradation of DCF. Moreover, the probable photocatalytic mechanisms for the degradation of DCF had been proposed based on the active species quenching experiments. The eleven degradation products were detected by HPLC-MS, and the degradation reaction pathway of DCF was deduced. Additionally, the CIS/Bi/BMO photocatalyst exhibited a consistently high removal rate after four cycles. This study proposes a new strategy for designing efficient S-scheme/Schottky heterojunction photocatalysts for solar energy conversion.

Thermal treatment impact on the evolution of active phases in layered double hydroxide-based ZnCr photocatalysts: Photodegradation and antibacterial performance

Abstract This study investigated the influence of thermal treatment on the photocatalytic performance of ZnCr layered double hydroxide-based mixed metal oxides in the degradation of methylene blue and brilliant cresyl blue organic dyes under simulated solar light irradiation. The photocatalysts were synthesized using a simple coprecipitation method and subjected to thermal treatment at temperatures ranging from 100°C to 900°C. Additionally, the study explored the antibacterial activity against Escherichia coli and Staphylococcus aureus using a novel antibacterial experimental setup. It not only involved the introduction of ZnCr samples into BioPeptone/prepared cell suspension to enhance photocatalyst–bacteria cell contact but also included research on antibacterial activity induced by solar irradiation and also in the absence of light, providing crucial insights into photocatalytic antibacterial activity of ZnCr photocatalysts. Despite satisfactory efficiencies observed for all thermally treated ZnCr samples (removal efficiency ranging from 40% to 90%), ZnCr 900 (thermally treated at 900°C) exhibited exceptional performance, achieving nearly 100% removal efficiency and complete growth inhibition for both bacteria. Integrating these findings with structural and textural characterization data, as well as kinetic studies, our comprehensive analysis enhances the understanding of structure-dependent photocatalytic activities. These insights open possibilities for the application of ZnCr photocatalysts in water purification and environmental remediation.

Heterostructures based on g-C<sub>3</sub>N<sub>4</sub> for the photocatalytic CO<sub>2</sub> reduction

The interest of the global scientific community in the problems of CO<sub>2</sub> utilization and returning to the carbon cycle has markedly increased in recent years. Among various CO<sub>2</sub> transformation processes, photocatalytic reduction is one of the most promising. Currently, much attention is paid to photocatalysts based on graphitic carbon nitride, since the use of g-C<sub>3</sub>N<sub>4</sub> makes it possible to perform CO<sub>2</sub> reduction under visible or solar light irradiation. To increase the reduction efficiency, g-C<sub>3</sub>N<sub>4</sub> is subjected to various modifications with the most popular and promising approach being the synthesis of composite photocatalysts based on g-C<sub>3</sub>N<sub>4</sub> with other semiconductors to form heterostructures. Depending on the type of semiconductor, transfer of photogenerated charge carriers in these systems can occur by various mechanisms, which largely determine the course of the process and the rates of formation of reaction products. This review addresses studies on the synthesis of composite photocatalysts based on g-C<sub>3</sub>N<sub>4</sub>, with emphasis being placed on the mechanisms of charge carrier transfer and the distribution of products of CO<sub>2</sub> reduction. <br>The bibliography includes 235 references.

Boosted photocatalytic hydrogen evolution of S-scheme N-doped CeO2-δ@ZnIn2S4 heterostructure photocatalyst

The advancement of highly effective heterojunction photocatalysts with improved charge separation and transfer has become a crucial scientific perspective for utilizing solar energy. In this study, we developed the S-scheme heterostructure by depositing N-doped CeO2-δ (NC) nanoparticles onto two-dimensional ZnIn2S4 (ZIS) nanosheets via hydrolysis strategy for significantly enhanced photocatalytic hydrogen evolution reaction. The optimal H2 generation rate of ∼ 798 μmol g–1 h–1 was achieved for NC-3@ZIS under solar light irradiation, which is about 18 and 2 times higher than those of pristine CeO2 (∼44 μmol g–1 h–1) and ZIS (∼358 μmol g–1 h–1), respectively. The photogenerated electrons from NC interact with the photogenerated holes of ZIS driven by an internal electric field, confirmed by In-situ KPFM, DFT calculation, and XPS results. According to EPR and photoelectrochemical measurements, NC-3@ZIS composite shows dramatically high separation efficiency of photogenerated charge carriers. This study provides a new approach for developing non-noble metal S-scheme heterojunctions with enhanced photocatalytic hydrogen evolution.

Influence of morphology and composition of spherical layered double hydroxide particles and derived mixed oxides on photocatalytic CO2 reduction

Considering the flexibility in the synthesis that allows the formation of materials with more than two metals, the present study reports the preparation of trimetallic layered double hydroxides (LDHs) having Al as structural tri-positive cation, Ti as photocatalytically active d0 transition metal and either Ni or Co as dipositive cation. In addition, these LDHs were used as precursors of the corresponding trimetallic mixed oxides (MO). LDH and MO materials in combination with Ru(bpy)3Cl2 as photosensitizer and triethanolamine as sacrificial electron donor were used as catalysts for CO2 reduction under solar light irradiation. A different product selectivity, either CH4 for Ni-LDH or CO and H2 for Co-MO, was observed with production rates for CH4 or CO that are among the highest reported for these systems. The role of the inorganic materials in the photocatalytic process was supported by transient absorption spectroscopy that revealed the quenching of the Ru(bpy)3Cl2 triplet excited state by Ni-LDH or Co-MO. An important finding was that the trimetallic Co-Ti-Al oxide with cobaltite structure is able to perform CO2 reduction in spite that the reduction potential of its conduction band is not sufficient to perform the process, evidence by photoluminescence revealing the existence of an upper electronic state responsible for the reduction. These results show the interest in screening multimetallic materials in photocatalysis due to their improved performance and diverse properties.

Tailoring MOF-5 Photocatalysts: Low-Temperature Synthesis and Solvent Variations for Enhanced Performance in Dye Degradation

Metal-organic frameworks (MOFs) are emerging as pivotal porous crystalline materials with diverse applications. Typically, MOFs are synthesized using solvothermal techniques at high temperatures and pressures. In this study, a novel approach was employed to synthesize zinc-based MOFs, specifically MOF-5, at low temperatures (up to 50 °C) via chemical mixing at standard pressures. Varying the temperature and solvents, N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF), in the chemical mixing process, the highest yield of the material was observed with DMF at 50 °C (M1). Two additional samples, M2 and M3, are synthesized at room temperature using DMF and NMP, respectively. Despite similarities in XRD, Raman, and FTIR analyses confirming successful MOF-5 formation, noticeable differences in sample morphology arise due to distinct synthesis conditions, particularly solvent and temperature variations. The MOF-5 samples exhibit UV absorption with varying band gaps. Notably, when employed as photocatalysts for organic dye (methylene blue) degradation, M2 outperforms others, achieving an impressive 85% degradation under simulated solar light irradiation. This work underscores the significance of tuning MOF photocatalyst properties through tailored synthesis routes, recognizing the profound impact of morphology and elemental composition on enhancing photocatalytic dye degradation performance. Copyright © 2024 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Novel magnetic separable BiOBr@Fe3O4 p-n heterostructure with highly efficient photocatalytic property toward organic pollutants

In this work, by considering good photocatalytic activity and p-type property but insufficient visible light absorbing property of BiOBr and excellent light absorption, n-type property of Fe3O4 that has poor photocatalytic property due to fast recombination of charge carriers having narrow bandgap, a solar light-active BiOBr@Fe3O4 p-n heterostructure was designed and synthesized for the first time using a versatile chemical precipitation method, combining the p-type BiOBr with the n-type Fe3O4. The developed photocatalyst underwent comprehensive investigation using various high-precision techniques. Its photocatalytic properties were assessed for the photodegradation of organic contaminants, such as Congo red (CR) and rhodamine B (Rh B), under solar light irradiation. The degree of mineralization of these pollutants by the BiOBr@Fe3O4 p-n heterostructure during photodegradation was also evaluated. Additionally, the photodegradation pathway was examined using LC-MS, and a possible mechanism were proposed. The findings reveal that the developed BiOBr@Fe3O4 p-n heterostructure exhibited exceptional photocatalytic performance, degrading 100% and 81% of Rh B and CR, respectively. Kinetic findings also indicate that the rate of photodegradations of the pollutants by the BiOBr@Fe3O4 heterostructure is approximately 7.2 and 3.4 times higher than that of pure Fe3O4 for the degradation of CR and Rh B, respectively. Besides, the developed heterojunction exhibited better photocatalytic performance than existing photocatalysts for photodegradation of CR and Rh B. The total organic carbon content (TOC) analysis further demonstrates the exceptional mineralization properties of the fabricated photocatalyst toward the pollutants. Therefore, the developed BiOBr@Fe3O4 p-n heterostructure shows promise in the treatment of these organic pollutants, contributing significantly to environmental remediation, particularly in photocatalysis.

Degradation of rhodamine B dye under visible and solar light on zinc oxide and nickel-doped zinc oxide thin films

The kinetic investigation of rhodamine B dye's photocatalytic degradation, chosen as a model pollutant, was conducted at room temperature using Zinc oxide (ZnO) and nickel-doped zinc oxide (Zn0.97Ni0.03O) photocatalysts synthesized through the spray pyrolysis method. XRD analysis confirmed the formation of hexagonal ZnO and Zn0.97Ni0.03O films, with crystallite sizes ranging from 19 to 29 nm and varying in mean average grain size from 72 nm to 88 nm. The surface morphology of the Ni-doped ZnO films was influenced by nickel doping, observed through SEM and TEM micrographs, revealing a dense structure of spherical-shaped crystals. Light transmission and optical band gap energy of the films ranged between specified values, ranging from 3.27 to 3.24 eV. The degradation process was assessed under various conditions, including different light sources (UV lamp and solar irradiation), pH levels, and substrate concentrations. Degradation followed a pseudo-first-order kinetic model, with rate constants (k) and half-life times (t1/2) calculated accordingly. The degradation efficiency of undoped ZnO and ZnO doped with nickel decreased with increasing concentration under UV irradiation from (0.1–0.5 M) under UV irradiation decreased from (34.29–45.02) (49.61–56.61), while under visible light are (40–45.07 %) (58.46–60.24 %), removal rates ranged within specific percentages. The porous Zn0.97Ni0.03O synthesized at 0.5 M exhibited the highest photocatalytic efficiency due to its enhanced crystallinity, resulting in degradation rates of 9.22 and 11.22 × 10−3 min−1 and half-life times of 75.18 and 61.77 min at 90 min specified for both UV and solar light irradiations, respectively. Acidification of the reaction medium accelerated the photocatalytic degradation kinetics, while alkalization slowed it down. These findings mark a significant advancement in the utilization of oxide semiconductors for water pollutant degradation under natural sunlight.

A facile method for boosting the graphitic carbon nitride's photocatalytic activity based on 0D/2D S-scheme heterojunction nanocomposite architecture

Graphitic carbon nitride (g-C3N4) has received significant interest as a metal-free photocatalyst. The S-scheme photocatalytic system has great potential to improve the charge separation in semiconductor photocatalysts. In this study, we have fabricated non-toxic and low-cost photocatalytic nanocomposites of 0D/2D S-scheme heterojunction composed of iron oxide and graphitic carbon nitride by a facile method. The developed facile method provides a sustainable way with a high atom economy to further enhance the photocatalytic performance of exfoliated g-C3N4. The 0D-iron oxide/2D-C3N4 exhibited nearly 10 times better than bulk g-C3N4 and almost 60 % better than exfoliated g-C3N4 under simulated solar light irradiation. The experimental results demonstrated that the effective charge-carrier mechanism led to an improved generation of reactive oxygen species (ROSs), resulting in an impressive photocatalytic performance. A serial photocatalytic test was also conducted to understand photocatalytic reaction mechanisms with various scavengers.

Unraveling the solar and visible light-induced deactivation mechanism of Pt-decorated carbon/TiO2 nanocomposite in photocatalytic hydrogen production

Photocatalytic water splitting presents an attractive and environmentally friendly method for generation of "green" hydrogen. However, the most widely used photocatalyst for hydrogen production, Pt-doped TiO2, has low stability, thus limiting its application for long term performance. In this study, the deactivation mechanism of Pt-decorated carbon TiO2 nanocomposite photocatalysts during photocatalytic hydrogen production was thoroughly investigated under solar and visible light irradiation. Solar light irradiation promoted markedly higher H2 production activity, however with lower catalyst stability. Deactivation studies using fresh catalysts/deactivated solutions and deactivated catalysts/fresh solutions point out the effect of the light used on the catalyst stability through changes on the catalyst surface as well as by the kinetics of intermediate/products formation during the reaction course. The present study revealed the importance of charge transport direction between TiO2, carbon and Pt on catalyst activity and stability and highlights the difference in visible and solar light-induced hydrogen production.

Platinum-Modified Rod-like Titania Mesocrystals with Enhanced Photocatalytic Activity

Photocatalysis is considered as an environmentally friendly method for both solar energy conversion and environmental purification of water, wastewater, air, and surfaces. Among various photocatalytic materials, titania is still the most widely investigated and applied, but more efforts must be carried out considering the synthesis of highly efficient photocatalysts for multifarious applications. It is thought that nanoengineering design of titania morphology might be the best solution. Accordingly, here, titania mesocrystals, assembled from crystallographically oriented nanocrystals, have been synthesized by an easy, cheap, and “green” solvothermal method (without the use of surfactants and templates), followed by simple annealing. The obtained materials have been characterized by various methods, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and diffuse reflectance spectroscopy (DRS). It has been found that the as-obtained photocatalysts exhibit a unique nanorod-like subunit structure with excellent crystalline and surface properties. However, pristine titania is hardly active for a hydrogen evolution reaction, and thus additional modification has been performed by platinum photodeposition (and silver as a reference). Indeed, the modification with only 2 wt% of noble metals results in a significant enhancement in activity, i.e., ca. 75 and 550 times by silver- and platinum-modified samples, respectively, reaching the corresponding reaction rates of 37 μmol h−1 and 276 μmol h−1. Additionally, titania mesocrystals exhibit high oxidation power under simulated solar light irradiation for the degradation of antibiotics within the tetracycline group (tetracycline (TC), ciprofloxacin (CIP), norfloxacin (NOR) and oxytetracycline hydrochloride (OTC)). It has been found that both experimental results and the density functional theory (DFT) calculations confirm the high ability of titania mesocrystals for oxidative decomposition of tetracycline antibiotics.

Simulated solar light-driven degradation of micropollutant in water by biochar-based metal-free catalyst: Regulation strategies for electronic structure and morphology engineering

The biochar/h-BN/g-C3N4 (BNC) composite photocatalyst with a spherical sheet cluster structure, was successfully synthesized. Under simulated solar light irradiation, the photocatalytic degradation rate of reactive red 120 by BNC was 87.94 % within 90 min, corresponding to a 3.57-fold higher kinetic constant than that of g-C3N4. The band structure and electron transfer path in BNC were determined using characterizations and density functional theory (DFT) calculations, confirming a type II heterojunction forming. The attraction of h-BN to h+ by electrostatic interaction and biochar's capacity for both electron transfer and storage were confirmed. Doping of biochar was also found to enhance light absorption and provide O vacancy. The existence of piezoelectric effect assisted the movement of photogenerated carriers to the material surface. In the system, the main active oxidation species were h+ and ·O2–. By calculating optical characteristics, the practical activity of photocatalysts is evaluated. Results indicated that the optimal dosage of BNC was 0.5 g/L in the planar reactor, corresponding to an optical thickness of 2.61 calculated by the six-flux radiation absorption–scattering model (SFM). Biochar doping was found to enhance light absorption. A novel photocatalytic mechanism was proposed for promising matel-free BNC.

Effortless Fabrication of Bi2O3‐Co3O4 Nanocomposite Catalyst: Harnessing Photocatalytic Power for Efficient Cationic Dye Degradation

AbstractA cost‐effective and simple co‐precipitation approach was used to create an efficient photocatalyst Co3O4‐Bi2O3 with identical stoichiometry (1 : 1 of both Co3O4 and Bi2O3). XRD, FTIR, TEM, SEM‐EDS, XPS, UV‐DRS, PL, BET, and TGA were used to characterize the produced material‘s structural and optical properties. The presence of a single phase spinel structure with a distinctive plane (311) was verified by the XRD peak of 2 at 36.9° for Co3O4‐Bi2O3. The SEM pictures revealed clustered consolidated spheres, suggesting particle homogeneity and high interconnectedness. The HR‐TEM and SAED pictures revealed an average crystallite size of 28 nm for the Co3O4‐Bi2O3 heterojunction. The UV‐DRS spectral data demonstrated a 2.1 eV reduction in band gap energy for Co3O4‐Bi2O3 (whereas Co3O4 is 2.4 eV and Bi2O3 is 2.7 eV). Under solar light irradiation, pristine Co3O4, Bi2O3, and Co3O4‐Bi2O3 composites were investigated for photocatalytic degradation of Methylene Blue (MB) and Malachite green (MG) dyes. By adjusting factors such as pH, starting dye concentration, catalyst dosage, and agitation duration, the optimal efficiency was determined. The acquired results showed Co3O4‐Bi2O3 ′s superior activity over both precursors. The composite obtained maximal degradation of 98 % (at pH=11) and 97 % (at pH=9) for MB and MG, respectively. The enhanced photo degradation activity of Co3O4‐Bi2O3 can be due to larger visible light absorption, increased surface area, and decreased h+/e− recombination. The reactive species trapping study was performed to determine the importance of superoxide and hydroxyl radicals during photo degradation. Dye degradation was governed by a pseudo‐first‐order kinetic model. The reusability and stability of Co3O4‐Bi2O3 were confirmed by utilizing the same material for five consecutive runs with both MB and MG dyes. Mass spectra analysis provided insights into the successful degradation of dyes, elucidating intermediate products. The synthesized Co3O4‐Bi2O3 nanocomposite offers unrivalled advantages in terms of structural and optical properties, superior photocatalytic activity, and remarkable stability, making it a promising candidate for efficient dye degradation applications without the formation of toxic by‐products.

ZnAl LDH-based Derivative Materials as Photocatalysts: Synthesis, Characterization, and Catalytic Performance in Tetracycline Degradation

Layered Double Hydroxide (LDH)-derived materials exhibited different characteristics from LDH precursors. The conversion of ZnAl LDH into its derivative material has been carried out to find the best catalyst for TC degradation. ZnAl (LDH)-based catalysts in this study have been effectively synthesized using coprecipitation, calcination, and restacking procedures. ZnAl Layered Double Oxide (LDO) is derived from the calcination of ZnAl LDH at 500°C. ZnAl LDH was also modified by adding Garcinia mangostana pericarp extract (GME). XRD, FT-IR, UV-DRS, and SEM-EDX were used to investigate the synthesized catalyst. ZnAl LDH exhibited the typical LDH FT-IR spectra, whereas ZnAl LDO showed metal oxide-like spectra, and the ZnAl-GME composite displayed the combination spectra of precursor material. The ZnAl LDH XRD diffraction pattern exhibited the attributes of a layered material, whereas the other three catalysts did not. Calcination destroyed the layered structure of ZnAl LDH, whereas the addition of GME to LDH and LDO generated a single-layered composite. The modified ZnAl-GME composite showed a decrease in both particle size and bandgap energy. At an ideal pH of 5, the synthesized catalyst was used in a batch system photodegradation of 5 mg/L Tetracycline (TC), employing solar light irradiation. ZnAl LDO holds the most significant catalytic activity and structural stability through the fifth regeneration cycle, degraded TC up to 100% in 90 minutes.

Synthesis and photocatalytic activity of BiOI particles: An efficient visible-light-driven degradation of organic pollutants in aqueous environments

Bismuth oxyiodide (BiOI) particles were successfully fabricated through solvothermal activation using bismuth (III) nitrate pentahydrate and potassium iodide as precursors. The photocatalytic activities of BiOI were investigated under the influence of synthesis temperature (120–200 °C) with a fixed duration of 12 h. The physical-chemical properties of the samples were systematically investigated using X-ray diffraction, scanning electron microscopy, N2-sorption isotherm techniques, and pH of the point of zero charge (pHpzc). The prepared BiOI exhibited a single phase with a non-uniform 2D morphology with different sizes, an average crystallite size of 30 nm, and a BET surface area of 20.71 m²g−1. The zero-point charge was determined to be 7.7. The photocatalytic performance under simulated solar light irradiation was investigated by examining the effects of dye initial concentration, catalyst dose, and dye pH. Remarkably, BiOI synthesized at 160 °C demonstrated an impressive 85% removal efficiency of 10 ppm MO (methyl orange) at normal pH levels (pH 6.8) within 120 min under visible light irradiation, along with the highest rate constant of 0.01418 min−1. The quenching effects of different scavengers indicate the significant role of reactive O2•– and a minor role of hVB+ and •OHads in the photocatalytic process. These findings underscore the potential of BiOI particles as efficient photocatalysts for environmental applications, particularly in the degradation of organic pollutants in water using solar light irradiation.

Ultrafast photosensitized degradation of xanthates by using methylene blue as photosensitizer under simulated and natural solar light irradiation: Operational parameters, mechanism and toxicity evolution

Xanthates have attracted considerable attention due to their broad applications in mineral flotation process and unique natures including environmental persistence and toxicity. This study proposed an innovative approach for the efficient xanthates treatment from mineral processing wastewater. Methylene blue (MB) with good water solubility and strong light absorption in visible range was used as the photosensitizer to degrade potassium ethyl xanthate (PEX) under homogeneous conditions. MB, even at a very low concentration (0.5 mg/L), was found to rapidly remove PEX in only 10 min whether under simulated or natural solar light irradiation. Besides, the influences of various operational parameters, including photosensitizer dosage, PEX concentration, pH, light intensity, common ions, and water source on the photosensitized oxidation process was evaluated and analyzed. The possible degradation path of PEX was investigated depending on the intermediates detected by Liquid chromatography-mass spectrometry (LC-MS), and the photosensitized degradation mechanism was further speculated and validated by the radicals quenching experiments and electron paramagnetic resonance (EPR) spectroscopy. Furthermore, the toxicity of PEX was assessed against Bullfrog tadpole and Lemna minor, and it was found to be greatly reduced after treating with MB photosensitization. Overall, it is the first time that MB is proved to be an outstanding candidate for actual flotation wastewater treatment, providing a more efficient, economical and greener alternative to conventional methods.

Highly visible-light-active sulfur and carbon co-doped TiO2 (SC-TiO2) heterogeneous photocatalysts prepared by underwater discharge plasma

To promptly and simply create highly crystalline S/C co-doped TiO2 (SC-TiO2) photocatalysts at room temperature and atmospheric pressure, we suggest a novel plasma-assisted sol-gel synthesis method. This method is a simultaneous synthetic process, in which an underwater plasma undergoes continuous reactions to generate high-energy atomic and molecular species that enable TiO2 to achieve crystallinity, a large surface area, and a heterogeneous structure within a few minutes. In particular, it was demonstrated that the heterogeneously structured TiO2 was formed by doping that sulfur and carbon replace O or Ti atoms in the TiO2 lattice depending on the composition of the synthesis solution during underwater plasma treatment. The resultant SC-TiO2 photocatalysts had narrowed bandgap energies and extended optical absorption scope into the visible range by inducing the intermediate states within bandgap due to generation of oxygen vacancies on the surface of TiO2 through synthesis, crystallization, and doping. Correspondingly, SC-TiO2 showed a significant degradation efficiency ([k] = 6.91 h−1) of tetracycline (TC, antibiotics) under solar light irradiation, up to approximately 4 times higher compared to commercial TiO2 ([k] = 1.68 h−1), resulting in great water purification. Therefore, we anticipate that this underwater discharge plasma system will prove to be an advantageous technique for producing heterostructural TiO2 photocatalysts with superior photocatalytic efficiency for environmental applications.

NiFe2O4/CuO heterostructures optical, magnetic and photocatalytic properties: Methylene blue dye degradation under solar light irradiation

A series of NiFe2O4/CuO heterostructures were prepared and their photocatalytic potential was compared with bare NiFe2O4 (NFO) and CuO (CO). The prepared materials were subjected to characterization using a combination of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, and UV–visible (UV–Vis) spectroscopy techniques. Photocatalytic efficiency was studied for removing methylene blue (MB) dye under solar light irradiation. The NiFe2O4/CuO heterostructures demonstrated superior removal of MB dye versus other materials. The decline in PL intensity for heterostructure revealed a low recombination rate of charge carriers. Maximum dye removal over NiFe2O4/CuO heterostructure was achieved for 20 mg/L dye catalyst dose and 20 mg/L dye solution at pH 10. Scavenging studies showed that hydroxyl radicals and electrons played a major role in the degradation of dye. The removal efficiency was 80.01 %, which was reduced to 78.83 % for NiFe2O4/CuO heterostructures after four consecutive cycles, which indicates its high stability under solar light irradiation. The NiFe2O4/CuO heterostructures may find potential applications in water treatment for removing organic dyes under visible light owing to their robust catalytic performance under solar light irradiation.