Photocatalytic Degradation Process Research Articles

A novel ternary Ti-V-Bi oxide photoelectrocatalyst in advanced oxidation process

Photoelectrocatalytic pollutant degradation is one of the most promising advanced oxidation processes for wastewater treatment. However, its efficiency dramatically depends on the development of photoelectrocatalyst materials. Therefore, here, ternary Ti0.2-Vx-Bi(0.8−x)-oxides (x = 0.15, 0.3, 0.4, 0.5, and 0.65) were applied as the photoelectrocatalysts for pollutant degradation. The photoelectrocatalysts were synthesized by a dip-coating thermal decomposition (DCTD) method. The physical and optical characteristics of photoelectrocatalysts were analyzed by XRD, FE-SEM, EDS, PL, and DRS tests. The photo/electrochemical behavior of samples was studied by LSV, EIS, and chronoamperometry with and without visible light illumination. The activity of samples was investigated by photocatalytic, electrocatalytic, and photoelectrocatalytic treatment of methyl orange and rifampin solutions under visible light irradiation. The kinetics of photocatalytic, electrocatalytic, and photoelectrocatalytic degradation processes was investigated by the Langmuir-Hinshelwood (L-H) kinetic model. Moreover, the mineralization extent of rifampin was studied by COD test. The results pointed to the optimum composition of ternary Ti0.2V0.4Bi0.4-oxide, in terms of both photocurrent and degradation time, which could completely degrade methyl orange and rifampin solutions in less than 15 min at a current density of 5 mA/cm2 under visible light irradiation. The superior performance of Ti0.2V0.4Bi0.4-oxide was attributed to its smaller particle size (larger surface area), lower band gap (2.1 eV), the lower recombination rate of e-/h+ pairs, and lower charge transfer resistance than the other compositions. The high activity and stability of Ti0.2V0.4Bi0.4-oxide introduce it as an efficient photoelectrocatalyst for pollutant degradation by the advanced oxidation process (AOP).

One-pot synthesis of Ag-modified SrTiO3: synergistic effect of decoration and doping for highly efficient photocatalytic NOx degradation under LED

Strontium titanate is an ideal cubic-structure perovskite oxide that finds application in hydrogen production and water pollutants degradation field. However, its photocatalytic activity is limited under UV irradiation due to its wide energy band bap (∼ 3.2 eV). To overcome this limitation, different strategies, such as metal-doping or metal-decoration, have emerged. Here, Ag-modified-SrTiO3 photocatalysts were prepared for the first time by a cheap, simple and sustainable approach based on the use of Ag-enriched wastewaters. The Ag-decorated SrTiO3 synthesized by a two steps method photodegraded by nearly 77% of NOx within 3 h. The Ag-modified SrTiO3 prepared by aone-pot synthesis led to a doubly modification of the oxide: Ag+ doping and Ag nanoparticles-decoration. In this case the use of Ag-enriched wastewaters led to poor photocatactivity of the photocatalyst, probably related to the presence of other metals in the waste. However, the use of a pure Ag precursor permitted the fabrication of a highly efficient material achieving complete photodegradation of NOx, exhibiting a photoactivity 4 times higher than bare SrTiO3 and 1.3 times more active than Ag-decorated material. The photocatalytic enhancement was attributed to the combined effect of Ag-doping and Ag-decoration on SrTiO3, which contributed to a narrow band gap (2.80 eV), as well as the formation of heterojunctions that promotes the separation of photogenerated charges, respectively. This material showed good stability during recycling tests, maintaining high performances after five cycles. Eventually, active species were identified using various scavengers by trapping holes and radicals generated during the photocatalytic degradation process.

Photo-Degradation Mechanism and Pathway for Tetracycline in Simulated Seawater Under Irradiation of Visible Light

To explore the mechanism and pathway for pollutant degradation in seawater by heterogeneous photocatalysts, the degradation of tetracycline (TC) in pure water and simulated seawater with different mesoporous TiO2 under the excitation of visible light was first investigated; then the effect of different salt ions on the photocatalytic degradation process was clarified. Combined with radical trapping experiments, electron spin resonance (ESR) spectroscopy, and intermediate product analysis, the main active species for photodegrading pollutants and the pathway of TC degradation in simulated seawater were investigated. The results showed that the photodegradation for TC in simulated seawater was significantly inhibited. Compared with the TC photodegradation in pure water, the reaction rate of the chiral mesoporous TiO2 photocatalyst for TC was reduced by approximately 70%, whereas the achiral mesoporous TiO2 photocatalyst could hardly degrade TC in seawater. Anions in simulated seawater had little effect on photodegradation, but Mg2+ and Ca2+ ions significantly inhibited the TC photodegradation process. Whether in water or simulated seawater, the active species generated by the catalyst after excitation by visible light were mainly holes, and each salt ion did not inhibit the generation of active species; thus, the degradation pathway both in simulated seawater and in water was the same. However, Mg2+ and Ca2+ would be enriched around the highly electronegative atoms in TC molecules, hindering the attack of holes to highly electronegative atoms in TC molecules, thereby inhibiting the photocatalytic degradation efficiency.

Structural regulatory mechanism of phosphotungstate acid decorated graphene oxide quantum dots-chitosan aerogel and its application in ciprofloxacin degradation

Chitosan modified AGQD (amine modified graphene oxide quantum dots) and then combined with H3PW12O40 to obtain CSx@AGQD-HPW12 via facile process and applied for CIP removal through pre-adsorption and photocatalytic processes. The application of chitosan could regulate the morphology and photoelectric properties effectively. CS0.5@AGQD-HPW12 was found to have the optimal CIP removal performance among all the products, the corresponding adsorption removal efficiency and pre-adsorption photocatalysis process were 72.1 % and 98.8 %, respectively. Results of toxicity assessment confirmed photocatalytic degradation process could mitigate the ecotoxicity of CIP effectively. The optimal TOC (total organic carbon) removal efficiency was about 52.1 %. Possible pathways for CIP degradation and reaction mechanism were proposed based on the results of intermediates analysis and trapping experiments. This demonstrated a novel approach to chitosan application and an eco-friendly way to remove CIP by adsorption-photocatalysis process.

Synthesis of TiO2/g-C3N5 heterojunction for photocatalytic degradation of methylene blue wastewater under visible light irradiation: Mechanism analysis

TiO2/g-C3N5 heterojunction is synthesized by the simple method, which is used in photocatalytic degradation methylene blue (MB) under visible light irradiation. The characterization analysis indicates that TiO2/g-C3N5 has good crystallinity, and the heterojunction between TiO2 and g-C3N5 is formed with good MB photocatalytic degradation performance. The MB photocatalytic degradation removal of the TiO2/g-C3N5 is 97.4 % at the concentration of 20 mg/L, which is significantly improved compared to the TiO2 and g-C3N5. The visible light adsorption ability and the separation of photogenerated carriers of the TiO2/g-C3N5 are improved, which is beneficial to the MB photocatalytic degradation. TiO2/g-C3N5 has good reusability with 95.8 % of the initial removal after 5 cycles. The capture experiment and electron paramagnetic resonance spectroscopy analysis indicate that the existence of the h+, O2− and OH involves in MB photocatalytic degradation process. MB photocatalytic mechanism of the TiO2/g-C3N5 is consistent with the direct Z scheme mechanism based on the band gap structure calculations.

Synergistic influence of vanadium pentoxide-coupled graphitic carbon nitride composite for photocatalytic degradation of organic pollutant: Stability and involved Z-scheme mechanism

The removal of dyes from wastewater by photocatalytic technologies has received substantial attention in recent years. In the present study, novel Z-scheme V2O5/g-C3N4 photocatalytic composites were organized via simple hydrothermal processes and a sequence of several characterization aspects. The degradation results showed that the optimum Z-scheme GVO2 heterostructure composite photocatalysts (PCs) had a better efficiency (90.1%) and an apparent rate (0.0136 min−1) for the methylene blue (MB) aqueous organic dye degradation, which was about 6.18-fold higher than that of pristine GCN catalyst. Meanwhile, the GVO2 heterostructured PCs showed better recycling stability after five consecutive tests. Moreover, the free radical trapping tests established that •O2− and h+ species were the prime reactive species in the photocatalytic MB degradation process in the heterostructured PCs. The photocatalytic enhanced activity was primarily recognized as the synergistic interfacial construction of the Z-scheme heterojunctions among V2O5 and GCN, which improved the separation/transfer, lower recombination rate, extended visible-light utilization ability, and enhanced reaction rate. Therefore, the existing study affords a simple tactic for the development of a direct Z-scheme for photocatalytic heterojunction nanomaterials for potential environmental remediation applications.

Unveiling the selective cleavage-bond mechanism during the photocatalytic degradation process with pH-mediated BiVO4/BiPO4 dipole controlled and changed glyphosate electron cloud distribution

The selective cleavage-bond of glyphosate is still a major challenge, especially in biodegradation and chemical degradation like advanced oxidation process (AOP). In this work, we found that the BiVO4 and BiVO4/BiPO4 heterogeneous photocatalysts generated different intermediates during the photocatalytic degradation of glyphosate. The main intermediate product by the BiVO4 photocatalyst was aminomethylphosphonic acid (AMPA, reaching to 81%) with high biological toxicity, which means glyphosate was degraded through the AMPA pathway. While the BiVO4/BiPO4 heterogeneous photocatalysts showed a significant inhibition of the accumulated AMPA (31%) at pH = 4, leading to the generation of benign products, such as sarcosine, acetic acid and PO43-. More importantly, the BiVO4/BiPO4-2 photocatalyst barely generated AMPA (less than 5%) at pH = 10. The lower AMPA concentration in our experiments was not attributed to its rapid degradation rate because AMPA could not be degraded from acidic (pH = 4) to alkaline (pH = 10). It indicated that glyphosate suffered from two cleavage-bond pathways between the BiVO4 and BiVO4/BiPO4 heterogeneous photocatalysts, which had been proved by mass spectrometry (MS) results. The attenuated total reflectance Fourier transforms infrared (ATR-FTIR) spectrum and density function theory (DFT) demonstrated that the adsorption sites of the BiVO4/BiPO4-2 photocatalyst occurred on the phosphate group of glyphosate molecules at pH = 10, which facilitated the C–P bond cleavage and inhibited the formation of AMPA. We found that pH-mediated BiVO4/BiPO4 dipole controlled and changed glyphosate electron cloud distribution, played an important role in the selective cleavage-bond of glyphosate. These results revealed both scientific and environmental significance for the efficient degradation of glyphosate through benign intermediates in soil and water.

Magnetic graphene oxide supported plasmonic nanoparticles as visible-light driven photocatalysts: Experimental study and artificial intelligent modelling for tetracycline degradation

Designing a high-efficiency solar-activated photocatalyst is a distinctive approach to employing green, abundant solar energy to eliminate anthropogenic environmental contaminants, including pharmaceutical effluents. Herein, the novel plasmo-magnetic quaternary nanocomposite of Ag/CuO/α-Fe2O3/rGO, as an original photocatalyst, indicated enhanced photocatalytic efficiency in the visible range with improved synergistic effects of the individual constituent components. It was fabricated by photo-deposition of plasmonic Ag nanoparticles on the hydrothermally grown CuO/α-Fe2O3 p-n heterostructures on the monolayered graphene oxide (GO) surface. The GO and Ag precursor amounts were changed to optimize magnetic and photocatalytic properties. It was fabricated by photo-deposition of plasmonic Ag nanoparticles on the hydrothermally grown CuO/α-Fe2O3 p-n heterostructures on the monolayered graphene oxide (GO) surface. The GO and Ag precursor amounts were changed to optimize magnetic and photocatalytic properties. The fabricated samples were characterized by various techniques such as PXRD, FESEM/EDX/elemental mapping, Raman, DRS, N2 physisorption, PL, TEM, HR-TEM, XPS, VSM, and EIS. The obtained photocatalyst showed a significantly improved percentage of photocatalytic degradation (~73%) of the organic probe pollutant (tetracycline (TC), 30 mg/L) after 360 min of exposure to visible light. Furthermore, the coexistence of rGO single layer and silver nanoparticles led to extending the absorption edge to the visible region and the decrease of charge carrier recombination. The quenching experiments characterized OH•, h+, and O2•− as the active species in the photocatalytic degradation process. The developed ANN and ANFIS techniques successfully anticipated the degradation percentage of TC and illustrated close agreement with the experimental data (R2 =0.96). Moreover, sensitivity analysis determined the relative importance of input variables in the architecture of both artificial intelligence tools. These characteristics confirm the high feasibility of the synthesized photocatalyst for future environmental remediations such as hydrogen production, air purification, antiviral/antibacterial applications, and water/wastewater treatment.

Efficient Degradation of Oxytetracycline in a Novel Plug-In Three-Dimensional Photocatalytic Microreactor

The combination of a photocatalytic reaction and microfluidic technology is an increasingly popular method utilized to continuously degrade wastewater. In this work, a novel photocatalytic microreactor with TiO2 loaded on the channel center insert was designed and the photocatalytic degradation process of oxytetracycline (OTC) was investigated. Parameters such as TiO2 loading, OTC initial concentration, light intensity, and ion (NO3– and SO42–) concentrations were systematically investigated. The results show that the degradation efficiency of OTC was 56% under the optimal experimental conditions. Compared with the conventional miniaturized photocatalytic reactors, the reaction rate constant and space–time degradation efficiency of the plug-in three-dimensional photocatalytic microreactor proposed in this work were 1–2 orders of magnitude higher. In addition, dimensionless correlation was obtained to predict the degradation efficiency. This work provides a promising microfluidic technology for the process intensification of photocatalytic reaction and wastewater treatment.

Dopant-driven recombination delay and ROS enhancement in nanoporous Cd1-xCuxS heterogeneous photocatalyst for the degradation of DR-23 dye under visible light irradiation

Developing an efficient heterogeneous photocatalyst for environmental remediation and treatment strategies using visible light harvesting processes is promising but challenging. Herein, Cd1-xCuxS materials have been synthesized and characterized by precise analytical tools. Cd1-xCuxS materials exhibited excellent photocatalytic activity for direct Red 23 (DR-23) dye degradation in visible light irradiation. The operational parameters, like dopant concentration, photocatalyst dose, pH, and initial concentration of dye were investigated during the process. The photocatalytic degradation process follows pseudo-first-order kinetics. As compared to other tested materials, 5% Cu doped CdS material revealed superior photocatalytic performance for the degradation of DR-23 (k = 13.96 × 10−3 min−1). Transient absorption spectroscopy, EIS, PL, and transient photocurrent indicated that adding copper to the CdS matrix improved the separation of photo-generated charge carriers by lowering the recombination rate. Spin-trapping experiments recognized the photodegradation primarily based on secondary redox products, i.e., hydroxyl and superoxide radicals. According to by Mott-Schottky curves, photocatalytic mechanism and photo-generated charge carrier density were elucidated regarding dopant-induced valence and conduction bands shifting. Thermodynamic probability of radical formation in line with the altered redox potentials by Cu doping has been discussed in the mechanism. The identification of intermediates by mass spectrometry study also showed a plausible breakdown mechanism for DR-23. Moreover, samples treated with nanophotocatalyst displayed excellent results when tested for water quality metrics such as DO, TDS, BOD, and COD. Developed nanophotocatalyst shows high recyclability with superior heterogeneous nature. 5% Cu-doped CdS also exhibit strong photocatalytic activity for the degradation of colourless pollutant bisphenol A (BPA) under visible light (k = 8.45 × 10−3 min−1). The results of this study offer exciting opportunities to alter semiconductors' electronic band structures for visible-light-induced photocatalytic activity for wastewater treatment.

In-situ construction of Sn-doped BiOCl/Bi2WO6 heterojunction for excellent organic pollutants degradation: Insight into performance and mechanism

Heterojunction formation and metal doping are two prospective strategies for accomplishing efficient separation of charges. However, the photogenerated carriers’ separation efficiency still has space for ascension when one of them is utilized alone. In this study, Sn-BiOCl/Bi2WO6 composite was constructed by tin chloride etching to investigate the synergy of heterojunction and metal doping toward the elevated of photogenerated carrier’ separation efficiency. The Sn2+/Sn4+ redox couple and heterojunction interface promotes the charges separation and reactive oxygen species (ROS) generation, leading to the Sn-BiOCl/Bi2WO6 exhibits 2.75 and 1.95 times of photodegradation rates towards rhodamine B (RhB) compared to Bi2WO6 and BiOCl/Bi2WO6. Meanwhile, the Sn-BiOCl/Bi2WO6 behaves photocatalytic activation effect on bicarbonate and sulfite to boost excessive ROS generation during the process of photocatalytic degradation of ciprofloxacin (CIP). Furthermore, the possible RhB and CIP photodegradation pathways over Sn-BiOCl/Bi2WO6 were further explored by MS spectra. This study offers a reliable method to develop highly efficient photocatalyst for environmental remediation.

Degradation of wastewater from carbon capture plants using metal‐impregnated TiO2 photocatalyst

AbstractAmine‐based carbon capture (ABCC) is an advanced and cost‐effective technology used to reduce the effects of climate change by capturing emitted from different sources. Although it has been demonstrated commercially, amine degradation poses a significant threat to humans and aquatic life. Amine degradation produces a wide variety of complex products such as nitrosamines and some organic acids. Some of these products are carcinogenic and mutagenic in nature and have demonstrated acute toxicity for laboratory animals. In order to mitigate the adverse impact of these compounds on human health and aquatic life, heterogeneous photocatalysis, an advanced oxidation process which can degrade a wide variety of chemical species with potent reactive hydroxyl radicals, was considered for the degradation of these compounds. The photocatalytic degradation of N‐nitrosodiethylamine (NDEA), acetic acid, and formic acid were tested using TiO2 and metal‐impregnated TiO2 catalysts such as Fe, Co, Ni, and Cu. Various techniques, such as thermogravimetric analysis (TGA), UV–Vis, X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and X‐ray fluorescence (XRF) were used to characterize these catalysts. The operational parameters for the photocatalytic degradation process were chosen as solution pH, catalyst dose, and metal impregnation percentage (imp%), and they were optimized using response surface methodology (RSM). pH was found as an important factor, and its impact on the photocatalytic degradation efficiency was more significant than the other operational parameters. The average degradation efficiency of the compounds reached 93.1% for Fe‐TiO2, 92.08% for Co‐TiO2, 89.09% for Ni‐TiO2, 88.81% for Cu‐TiO2, and 86.3% for TiO2 at the optimum conditions.

The Removal of Sulfamonomethoxine (SMM) with Copper Oxide/Zirconium Dioxide (CuO/ZrO2) Nanocomposites by Photocatalytic Degradation in Pharmaceutical Industry Wastewaters and the Evaluation of Microtox (Aliivibrio fischeri) and Daphnia magna Acute Toxicity Assays

In this study, Copper oxide/zirconium dioxide (CuO/ZrO2) nanocomposites (NCs) as a photocatalys was examined during photocatalytic degradation process (PDP) in the efficient removal of Sulfamonomethoxine (SMM) from pharmaceutical industry wastewater (PI ww) plant, İzmir, Turkey. Different pH values (3.0, 4.0, 7.0, 9.0, 10.0 and 12.0), increasing SMM concentrations (5, 10, 20 and 40 mg/l), increasing CuO/ZrO2 NCs concentrations (100, 200, 400, 800 and 1000 mg/l), different CuO/ZrO2 NCs mass ratios (1/2, 2/3, 3/4, 4/4, 4/3, 3/2, 2/1), increasing recycle times (1., 2., 3., 4., 5., 6. and 7.) was operated during PDP in the efficient removal of SMM in PI ww. The characteristics of the synthesized nanoparticles (NPs) were assessed using XRD, DRS, FESEM, EDX, FTIR, TEM and XPS analyses, respectively. The acute toxicity assays were operated with Microtox (Aliivibrio fischeri also called Vibrio fischeri) and Daphnia magna acute toxicity tests. The photocatalytic degradation mechanisms of CuO/ZrO2 NCs and the reaction kinetics of SMM were evaluated in PI ww during PDP. Cost analysis was evaluated for SMM removal with CuO/ZrO2 NCs by PDP in PI ww. ANOVA statistical analysis was used for all experimental samples. Maximum 99.6% SMM removal was obtained during PDP in PI ww, at 350 W UV-vis light irradiation power, at 147 mW/cm2 light intensity, after 120 min, at pH=12.0 and at 25oC, respectively. Maximum 99.2% SMM removal was found with PDP in PI ww, at 5 mg/l SMM, at 350 W UV-vis, at 147 mW/cm2, after 120 min, at pH=12.0 and at 25oC, respectively. Maximum 99.5% SMM removal was measured to 800 mg/l CuO/ZrO2 NCs with PDP in PI ww, at 5 mg/l SMM, at 350 W UV-vis, at 147 mW/cm2, after 120 min, at pH=12.0 and at 25oC, respectively. Maximum 99.4% SMM removal was measured at 4/3wt CuO/ZrO2 NCs mass ratios, at 5 mg/l SMM, at 800 mg/l CuO/ZrO2 NCs, at 350 W UV-vis, at 147 mW/cm2, after 120 min, at pH=12.0 and at 25oC, respectively. Maximum 99.5% SMM recovery was measured in PI ww during PDP, after 1. recycle time, at 5 mg/l SMM, at 800 mg/l CuO/ZrO2 NCs, at 4/3wt CuO/ZrO2 NCs mass rartio, at 350 W UV-vis, at 147 mW/cm2, after 120 min, at pH=12.0 and at 25oC, respectively. 97.31% maximum Microtox acute toxicity removal was found in SMM=20 mg/l after 180 min, and at 60oC. It was observed an inhibition effect of SMM=40 mg/l to Microtox after 180 min, and at 60oC. 93.27% maximum Daphnia magna acute toxicity removal was obtained in SMM=20 mg/l after 180 min, and at 60oC, respectively. It was obtained an inhibition effect of SMM=40 mg/l to Daphnia magna after 180 min and at 60oC. As a result, the CuO/ZrO2 NCs during PDP in PI ww was stable in harsh environments such as acidic, alkaline, saline and then was still effective process. Finally, the combination of a simple, easy operation preparation process, excellent performance and cost effective, makes this CuO/ZrO2 NCs a promising option during PDP in PI ww treatment.

Tailoring S-scheme-based carbon nanotubes (CNTs) mediated Ag-CuBi2O4/Bi2S3 nanomaterials for photocatalytic dyes degradation in the aqueous system

In this study, S-scheme-based hydrothermal synthesis of Ag-CuBi2O4/CNTs/Bi2S3 layered composites has been successfully reported. The photo-degradation of toxic dyes, viz. methyl orange (MO), and methylene blue (MB), has been used to examine nanocomposites with varying weight percent of Bi2S3 for photocatalytic activity in the visible range. Among candidates, Ag-CuBi2O4/CNTs/Bi2S3 with a 10% loading of Bi2S3 outperformed both pure and hybrid composites in photocatalytic activity. For MO degradation, the hybrid composite with 10% Bi2S3 loading degrades 7.04 times higher than pristine CuBi2O4 and Bi2S3 samples, and for MB degradation, it degrades 4.96 times higher than pristine samples. High surface area, less recombination rate of photogenerated charge carriers, photogenerated carriers faster separation, and high redox ability of Ag-CuBi2O4/CNTs/Bi2S3 (10%) are all attributed to the improving photocatalytic performance. Even after ten cycles, the hybrid composite is chemically stable and reusable. Carbon nanotubes (CNTs) are a transfer bridge in layered structure for electrons because of their coordinated Fermi level between Ag-CuBi2O4 and Bi2S3. In addition, the scavenger and electron spin resonance (ESR) experiments verified that ∙O2−, ∙OH, and h+ were the important reactive species that successfully facilitated the photocatalytic degradation process to degrade dyes. This study presents a straightforward and economical approach for obtaining a stable semiconductor-based photocatalytic system and a potential technique for future applications.

Efficiency and mechanism on photocatalytic degradation of fluoranthene in soil by Z-scheme g-C3N4/α-Fe2O3 photocatalyst under simulated sunlight.

Polycyclic aromatic hydrocarbons (PAHs) in soil have potential harm on human health. However, remediation of PAH-contaminated soils through photocatalytic technology remains a challenge. Therefore, the photocatalyst g-C3N4/α-Fe2O3 was synthesized and applied to photocatalytic degradation of fluoranthene in soil. The physicochemical properties of g-C3N4/α-Fe2O3 and various degradation parameters, such as catalyst dosage, the ratio of water/soil, and initial pH, were investigated in detail. In soil slurry reaction system (water/soil=10:1, w/w), the optimal degradation efficiency on fluoranthene was 88.7% after simulated sunlight irradiation for 12 h (contaminated soil=2 g, initial fluoranthene concentration=36 mg/kg, catalyst dosage=5%, and pH=6.8), and the photocatalytic degradation followed pseudo-first-order kinetics. The degradation efficiency of g-C3N4/α-Fe2O3 was higher compared with P25. Degradation mechanism analysis showed that •O2- and h+ are the main active species in photocatalytic degradation process of fluoranthene by g-C3N4/α-Fe2O3. Coupling g-C3N4 and α-Fe2O3 enhances the interfacial charge transport capacity via Z-scheme charge transfer route and inhibits the recombination of photogenerated electrons and holes of g-C3N4 and α-Fe2O3, then significantly improves the production of active species and photocatalytic activity. Results showed that photocatalytic treatment of soil by g-C3N4/α-Fe2O3 is an effective strategy for remediation of soils contaminated by PAHs.

Direct Z-scheme In2O3/AgI heterojunction with oxygen vacancies for efficient molecular oxygen activation and enhanced photocatalytic degradation of tetracycline

A novel In2O3/AgI heterojunction, which has a hollow tubular structure with AgI particles distributed evenly on the outer and inner surfaces of In2O3 microtubes, was fabricated from annealing of AgI adhered to MIL-68(In). The as-prepared heterojunction exhibited much higher photocatalytic activity towards tetracycline degradation compared to In2O3 and AgI. The presence of InAg-1 (1.0 g/L), which has a In2O3:AgI mole ratio of 2:1, could achieve 98.4% removal of tetracycline (20 mg/L) from the solution phase under visible light illumination in 10 min, and it had excellent reusability and stability. The In2O3/AgI heterojunction also exhibited excellent performance in photocatalytic degradation of tetracycline in different types of water matrices and under natural sunlight illumination, demonstrating its potential in practical application. The superior photocatalytic activity of InAg-1 is attributed to the heterojunction formation and generation of oxygen vacancies (OVs), which improve the separation efficiency of photoinduced e−-h+ pairs. Meanwhile, the built-in electric field (BIEF) formed with e- flowing from AgI to In2O3, which is confirmed by density functional theory calculations, helps the formation of a Z-scheme, instead of type II, heterojunction between In2O3 and AgI. Results of radical trapping experiments and electron spin resonance spectra reveal that 1O2, h+, •O2−, and •OH were the key reactive species involved in the photocatalytic degradation process. These findings indicate that Z-scheme photocatalysts with OVs could efficiently activate molecular oxygen and thus have excellent photocatalytic activity towards degradation of organic pollutants.

Enhancement of Photocatalytic Activity and Microstructural Growth of Cobalt-Substituted Ba1−xCoxTiO3 {x = 0, …, 1} Heterostructure

The photocatalytic degradation process and absorption kinetics of the aqueous solution of the Cibacron Brilliant Yellow 3G-P dye (Y) were investigated under UV-Vis light. Pure barium titanate BaTiO3 (BT) and cobalt ion-substituted barium Ba1−xCoxTiO3 (x = 0, …, 1) nano-compound powders (BCT) were synthesized using the sol–gel method and colloidal solution destabilization, and utilized as photocatalysts. The powder X-ray diffraction (PXRD) crystal structure analysis of the BT nanoparticles (NPs) revealed a prominent reflection corresponding to the perovskite structure. However, impurities and secondary phase distributions were qualitatively identified in the PXRD patterns for x ≥ 0.2 of cobalt substitution rate. Rietveld refinements of the PXRD data showed that the BCT nano-compound series undergoes a transition from perovskite structure to isomorphous ilmenite-type rhombohedral CoTiO3 (CT) ceramic. The nanoparticles produced displayed robust chemical interactions, according to a Fourier transform infrared spectroscopy (FTIR) analysis. The BT and BCT nanoparticles had secondary hexagonal phases that matched the PXRD results and small aggregated, more spherically shaped particles with sizes ranging from 30 to 114 nm, according to transmission electron microscopy (TEM). Following a thorough evaluation of BCT nano-compounds with (x = 0.6), energy-dispersive X-ray (EDX) compositional elemental analysis revealed random distributions of cobalt ions. Through optical analysis of the photoluminescence spectra (PL), the electronic structure, charge carriers, defects, and energy transfer mechanisms of the compounds were examined. Due to the cobalt ions being present in the BT lattice, the UV-visible absorption spectra of BCT showed a little red-shift in the absorption curves when compared to pure BT samples. The electrical and optical characteristics of materials, such as their photon absorption coefficient, can be gathered from their UV-visible spectra. The photocatalytic reaction is brought about by the electron–hole pairs produced by this absorption. The estimated band gap energies of the examined compounds, which are in the range of 3.79 to 2.89 eV, are intriguing and require more investigation into their potential as UV photocatalysts. These nano-ceramics might be able to handle issues with pollution and impurities, such as the breakdown of organic contaminants and the production of hydrogen from water.

High-gravity photocatalytic degradation of tetracycline hydrochloride under simulated sunlight

Oxygen can generate reactive oxygen species in photocatalysis, promoting organic matter's mineralization. Therefore, enhanced oxygenation of the photocatalytic degradation system will help improve photocatalytic degradation efficiency. This study developed a novel high-gravity photocatalytic degradation method, which leverages the robust gas–liquid mass transfer capability of a supergravity rotating bed to realize the enhanced oxygenation of the photocatalytic degradation system. Specifically, this study used graphitic carbon nitride as the catalyst and tetracycline hydrochloride as the model pollutant. The effects of packing thickness, catalyst concentration, liquid flow rate, rotor speed, gas flow rate, and initial pH value on photocatalytic degradation performance were investigated. The results showed that the degradation rate of tetracycline hydrochloride reached 84.6 % under the optimal conditions of the rotating packed bed, which was 14.8 % higher than that of the traditional photocatalytic degradation process.

The Use of a Novel Graphitic Carbon Nitride/Cobalt Molybdate (G-C3 n4 /ComoO4 ) Nanocomposites for the Doxycycline Removal by Photocatalytic Degradation in Pharmaceutical Industry Wastewaters and the Evaluation of Microtox (Aliivibrio Fischeri) and Daphnia Magna Acute Toxicity Assays

In this study, a novel graphitic carbon nitride/cobalt molybdate (g-C3 N4 /CoMoO4 ) nanocomposites (NCs) as a photocatalys was examined during photocatalytic degradation process in the efficient removal of Doxycycline (DOX) from pharmaceutical industry wastewater plant, İzmir, Turkey. Different pH values (3.0, 4.0, 6.0, 7.0, 9.0 and 11.0), increasing DOX concentrations (5 mg/l, 15 mg/l, 30 mg/l and 45 mg/l), increasing g-C3 N4 /CoMoO4 NCs concentrations (1 mg/l, 2 mg/l, 3 mg/l, 4 mg/l, 6 mg/l, 8 mg/l and 10 mg/l), different g-C3 N4 /CoMoO4 NCs mass ratios (5/5, 6/4, 7/3, 8/2, 9/1, 1/9, 2/8, 3/7 and 4/6), increasing recycle times (1., 2., 3., 4., 5., 6. and 7.) was operated during photocatalytic degradation process in the efficient removal of DOX in pharmaceutical industry wastewater. The characteristics of the synthesized nanoparticles (NPs) were assessed using X-Ray Difraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-Ray (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and Diffuse reflectance UV-Vis spectra (DRS) analyses, respectively. The acute toxicity assays were operated with Microtox (Aliivibrio fischeri also called Vibrio fischeri) and Daphnia magna acute toxicity tests. ANOVA statistical analysis was used for all experimental samples. The maximum 99% DOX removal efficiency was obtained during photocatalytic degradation process in pharmaceutical industry wastewater, at 150 W UV-vis light irradiation power, after 180 min photocatalytic degradation time, at pH=9.0 and at 25°C, respectively

Recent advances in synthesis, structural properties, and regulation of nickel sulfide-based heterostructures for environmental water remediation: an insight review.

Heterostructured nanomaterials exhibit pronounced potential in environmental science, including the water purification, pollutant monitoring, and environmental remediation. Especially, their application through advanced oxidation processes has been found capable and adaptable in waste water treatment. In semiconductor photocatalysts, metal sulfides are the leading materials. However, for further modifications, the progresses on specific materials need to be overviewed. Among metal sulfides, nickel sulfides are the emerging semiconductors due to relatively narrow band gaps, high thermal and chemical stability, and cost effectiveness. The aim of the present review is to conduct a thorough analysis and summary of recent progress in the application of nickel sulfide-based heterostructures in water decontamination. Initially, the review introduces the emerging needs of the materials for environment following the characteristics features of metal sulfides with emphasis on nickel sulfides. Subsequently, synthesis strategies and structural properties of nickel sulfide (NiS and NiS2)-based photocatalysts are discussed. Herein, controlled synthesis procedures to influence their active structure, compositions, shape, and size for the enhanced photocatalytic performances are also considered. Furthermore, there is discussion on heterostructures formed by metal modification, metal oxides, and carbon hybridized nanocomposites. In the continuation, the modified characteristics are investigated which favors the photocatalytic processes for degradation of organic contaminations in water. The overall study highlights significant improvements in degradation efficiency of hetero-interfaced NiS and NiS2 photocatalysts towards organics that are comparable to expensive noble-metal photocatalysts. Finally, we also added a little on prospects for future advancement of nickel sulfide-based photocatalysts for applications in sustainable environmental remediation.