Fabrication Of Photocatalysts Research Articles

The presence of Mo and O double vacancies in Bi2W0.25Mo0.75O6 solid solution promotes photogenerated charge separation and molecular oxygen activation for efficient removal of gaseous toluene under visible light

Enhancing indoor air quality and devising efficient technologies for the degradation of low-concentration volatile organic compounds (VOCs) represent pertinent topics in current research endeavors. In this study, a one-step hydrothermal method was employed to successfully synthesize a Bi2W0.25Mo0.75O6 solid solution photocatalyst featuring Mo and O double vacancies. The catalyst has excellent degradation effect on low concentration (30 ppm) gaseous toluene within 60 min of visible light irradiation, which can achieve 95.36 % in air atmosphere and 99.79 % in pure oxygen atmosphere. The incorporation of Mo vacancies in the solid solution photocatalyst proved instrumental in inhibiting carrier complexation, while O vacancies facilitated the activation of molecular oxygen. Concurrent Mo and O double vacancies extended the photo response range, expedited the transport of photogenerated charges, and diversified the reactive oxygen species pool, collectively enhancing toluene degradation. Hence, this study presents a compelling method for the fabrication of photocatalysts exhibiting visible light catalytic activity, with potential applications in the treatment and mitigation of real-world environmental pollution challenges under mild conditions.

3D/1D Fe3O4@TiO2/TC-TiO2/SiO2 Magnetic Inorganic-Framework Molecularly Imprinted Fibers for Targeted Photodegradation.

To achieve a selective degradation of pollutants in a water body, 3D/1D magnetic molecularly imprinted fibers Fe3O4@TiO2/TC-TiO2/SiO2 were fabricated by an electrospinning method. The molecularly imprinted layer was successfully prepared by a direct imprinting method using TiO2 as a functional monomer. Fe3O4 facilitates the catalyst recovery and light utilization. The as-prepared fibrous photocatalyst has a large specific surface area of 132.4 m2/g. The successful generation of imprinted sites was proven by various characterizations. The weak interaction between the inorganic functional monomer and tetracycline (TC) was determined to be van der Waals force and hydrogen bonds by the IGMH isosurface theory. The construction of the 3D/1D homojunction of molecularly imprinted materials is beneficial to charge transfer. The as-prepared photocatalyst exhibits a high selectivity coefficient α = 737.38 competing with RhB. The TC removal efficiency reached 100% within only 20 min. In addition, the possible degradation pathway and the degradation mechanism are reasonably proposed. This work not only provides an in-depth mechanism of the weak interaction between the inorganic molecularly imprinted functional monomer and pollutant molecules but also offers new thoughts on the fabrication of photocatalysts for the effective and selective treatment of pollutants in water bodies.

Efficient and easily recyclable photocatalytic reduction of Se(IV) from wastewater using stable TiO2/BiOBr/cloth: Mechanism insight and machine learning modeling

Photocatalytic technology is extensively employed for the reductive removal of water contaminants; however, it contends with low catalytic efficiency and challenges in catalyst recovery. In this study, we propose integrating experimental procedures with artificial intelligence modeling to enhance the purification of Se(IV)-contaminated wastewater. We present an efficient, easily recyclable, and cost-effective strategy for photocatalyst fabrication. Specifically, we develop a novel method for Se(IV) removal by immobilizing TiO2/BiOBr onto glass fiber cloth surfaces using chitosan for Se(IV) reduction in aqueous solutions. The TiO2/BiOBr/cloth (TB-4/cloth) catalyst achieves a remarkable 99.2 % Se(IV) removal within 2 h under visible light and maintains excellent Se(IV) reduction photocatalytic activity (86.4 %) even after eight cycles, remaining easily reusable. Additionally, we develop two machine learning models, namely artificial neural network (ANN) and long short-term memory (LSTM), to validate the anticipated experimental outcomes. Both models exhibit high accuracy and predictive capability (R2 > 0.99, RMSE < 0.03). This study introduces a novel approach that combines experimentation with artificial intelligence modeling, paving the way for future advancements in Se(IV)-contaminated wastewater purification methods.

3D-printed photocatalytic scaffolds of BiVO4 by direct ink writing for acetaminophen mineralization

A novel methodology to obtain 3D printable BiVO4 precursor scaffolds (3DM-BiVO4) via robocasting, showing excellent periodicity, shape retention, and mechanical stability, is disclosed for the first time. The ceramic pastes (solids at 70 wt.-%) comprised of BiVO4 precursor, SiO2NPs, and a solution of deionized water: ethylene glycol (volume ratio 1:2, DI water: EG) exhibited enhanced rheology for the 3D printing of self-supported structures (3DM-BiVO4). The thermal treatment induced a monoclinic scheelite phase, and the ethylene glycol contributed to achieving a unique square flake-like particle morphology. 3DM-BiVO4 scaffolds were used as reusable monolithic photocatalysts, showing 72% acetaminophen mineralization at 240 min and pH = 9. This innovative approach opens avenues for designing 3D printable ceramic pastes, offering potential applications in tailoring-made monolithic photocatalyst fabrication by using SiO2NPs as an inorganic binder.

Effective 1D/2D nanostructured S-scheme W18O49/g-C3N4 heterojunction photocatalyst fabrication for improved photocatalytic nitrogen fixation performance

The fundamental insights into the reaction mechanism, especially the electron transfer mechanism, are highly promising yet challenging for W18O49/g-C3N4 heterojunction catalysts during photocatalytic nitrogen fixation. Herein, the 1D/2D nanostructured S-scheme heterojunctions were designed by in situ growth of 1D W18O49 nanowires on 2D g-C3N4 nanosheets through solvothermal method using methanol as solvent. In situ XPS analysis revealed that electrons in the conduction band of W18O49 recombine with holes in the valence band of g-C3N4 under the conduction effect of internal electric field, band bending, and Coulombic attraction in the W18O49/g-C3N4 heterojunction. The photogenerated electrons are retained in g-C3N4, where the negative reduction potential of its conduction band enhances the activation of N2. As a result, the ammonia generation rate employing the optimal W18O49/g-C3N4 heterojunction is 64.8 μmol gcat−1 h−1, approximately double that of W18O49 alone and 2.3 times higher than that of g-C3N4. The enhanced activity and facile methodology make the current material exceedingly appealing for implementation in photocatalytic nitrogen fixation for the synthesis of ammonia.

Efficient utilization of ceramic waste (cyclone dust waste) for enhancing the photocatalytic performance of TiO2 nanoparticles toward Rhodamine B photodegradation

Owing to the increase in the world's population, industrial demands are significantly increasing, and air/water pollution has become a global threat that severely affects human health. Many pollutants are discharged into the ecosystem, ceramic dust/wastes cause air pollution and textile dyes are among the recalcitrant organic water pollutants. This requires efficient waste management and waste remediation. Photocatalysis is one of the most efficient technologies for treating organic pollutants, where TiO2 nanoparticles are the most widely used photocatalysts. However, the wide bandgap and rapid e-h recombination rates of TiO2 nanoparticles impede their practical applications. Herein, we are hitting “two birds with one stone” by utilizing ceramic waste powder in the fabrication of photocatalysts to degrade organic pollutants. The employed ceramic waste “cyclone dust waste (CDW)” was used as filler materials during the sol-gel synthesis of TiO2 photocatalyst. The synthesis method is a facile and cost-effective route because CDW was employed as obtained from the production line without any further processing. Different loading percentages of CDW were in-situ added to the TiO2 during the synthesis. x%CDW-TiO2 samples were investigated toward the photodegradation of Rhodamine B dye as a primary pollutant model, where 30%CDW-TiO2 nanocomposite was the optimum sample that achieved 2.6-fold enhancement in the RB photodegradation% compared to the bare TiO2. The physicochemical properties of the as-fabricated samples were investigated using different techniques, including XRD, HR-TEM, FE-SEM, DRS, and PL. It was found that the as-prepared CDW extended the light absorption capability of the 30%CDW-TiO2 nanocomposite toward the visible light. The PL results showed the reduction of e-h recombination rate in 30%CDW-TiO2 nanocomposite owing to the constructed Type-II/Z-scheme heterojunction. This work will open the door to the investigation of different wastes to be used as filler materials to be incorporated in the synthesis of value-added compounds.

A ternary rh/c-In2O3/CdIn2S4 heterostructure photocatalyst: In-situ construction and boosting high-efficient visible-light H2 production

Narrow band gap semiconductors have attracted more attention in photocatalytic. It is still a challenge to design heterojunction photocatalysts with efficient visible-light-harvesting and high redox ability water splitting hydrogen fuel production. Herein, a ternary heterojunction of rhombic phase In2O3 (rh-In2O3)/cubic phases In2O3 (c-In2O3) homojunction combined CdIn2S4 (rh/c-IO/CIS) was designed and constructed via in-situ pyrolysis of a liquid precursor. The as-synthesized rh/c-IO/CIS heterojunction exhibits a nanoplate structure composed of multilayers of tightly coupled ultrathin flakelets. The nanoflakelets stacking structure endows abundant exposed active sites and efficient visible-light-harvesting. Experimental results show rh/c-IO/CIS heterojunction follows a S-scheme mechanism proving high charge separation efficiency and strong redox capability. Thus, the catalyst exhibits excellent photocatalytic hydrogen production performance. The hydrogen evolution rate can get 4.7 mmol·g−1·h−1, it is 3.6 folds and 7.8 folds higher than that of CdIn2S4 and rh/c-In2O3. This work provides a new tack for rational design and fabrication of photocatalysts with enhanced photocatalytic hydrogen energy production performance.

Energy-Efficient MIL-53(Fe)/Sn3O4 Nanosheet Photocatalysts for Visible-Light Degradation of Toxic Organics in Wastewater

The fabrication of photocatalysts with preferable degradation ability is critical to purify wastewater. MIL-53(Fe), as a representative Fe-based metal–organic framework (Fe-MOF), has been widely used in photocatalysis due to its excellent intrinsic characteristics. However, the inadequate electron number in MIL-53(Fe) has restricted the ability of photodegradation of organic pollutants. Herein, desirable, energy-efficient, and environmentally friendly MIL-53(Fe)/Sn3O4 nanosheet photocatalysts were first constructed by the solvothermal method. The characterization results indicated that the MIL-53(Fe)/Sn3O4-5 (5 wt % Sn3O4) catalyst exhibited optimal photoelectric properties and maintained a relatively regular morphology. Moreover, the prepared MIL-53(Fe)/Sn3O4-5 exhibited preferable photodegradation ability for dyes and antibiotics under visible light, and the maximum photodegradation capacity for malachite green, methylene blue, tetracycline, ciprofloxacin, and ofloxacin could reach 96.9, 88.2, 70.3, 83.5, and 88.1%, respectively. The initial pH, photocatalyst dosage, and initial concentration were comprehensively investigated for degrading malachite green. In addition, we also explored the prepared catalyst for the removal of malachite green from different actual wastewater samples. After three cycles, the degradation efficiency of malachite green by MIL-53(Fe)/Sn3O4-5 decreased very little, exhibiting good reuse performance. The enhanced photodegradation efficiency of MIL-53(Fe)/Sn3O4-5 could be attributed to the construction of heterojunctions derived from a compact joint interface between Sn3O4 and Fe-MOF, which expedited the separation ability of photogenerated carriers and broadened the visible response range. The active species trapping experiments and electron spin-resonance results determined that many active species (h+, •OH, and •O2–) were involved in the photocatalytic process. Correspondingly, a convincible photodegradation mechanism between Sn3O4 and MIL-53(Fe) was proposed according to the experimental results. This study demonstrates that the fabricated Sn3O4 and MOF composites can provide a feasible solution for the purification of wastewater.

Novel approach towards ternary magnetic g-C3N4/ZnO-W/Snx nanocomposite: photodegradation of nicotine under visible light irradiation

ABSTRACT Nicotine, an exceedingly noxious alkaloid, has been reported as an emerging anthropogenic waste water contaminant for decades. The current study investigated the photocatalytic degradation of nicotine in aqueous medium. Novel g-C3N4/ZnO-W/Snx composites were fabricated by impregnation of g-C3N4 with ZnO-W and SnCl2.H2O. The XRD and FTIR data strappingly evidenced the proficient blending of g-C3N4, metal oxide and the metal used as dopant. SEM and EDS micrographs showed agglomerated morphology; layered structure with loopholes, which invetrate the elementalconfiguration of fabricated nanocomposites. Spectroscopic analysis shows red shift in the vicinity of 240–270 nanometre as a confirmation of increased Sn content. Optical analysis shows band gap tailoring (2.32–1.78 eV) with increased dopant metal content, which constrains the electron hole pair recombination. This results in the production of more ROS species in the reaction system, leading to significant increase in photoactive nicotine degradation from 24% g-C3N4/ZnO-W to 98% g-C3N4/ZnO-W/Sn(0.011). The rate constant R2 values 0.985, 0.988, 0.990, 0.992, 0.996 and 0.997 for the synthesised composites confirmed the pseudo-first-order kinetics and maximum photodegradation in acidic medium. Efficient outcomes of 98% degradation under visible light and striking recyclability results for the grown composite g-C3N4/ZnO-W/Sn (0.011) even after the fifth cycle was 93% evidenced that synthesised composite exhibits high reusability and mechanical stability. Inclusively, the present research provides an innovative approach for the fabrication of photo-catalysts in wastewater treatment.

Robust S-scheme ZnO-TiO2-Ag with efficient charge separations for highly active hydrogen evolution performance and photocatalytic mechanism insight

The design and fabrication of photocatalysts for robust H2 evolution from photocatalytic water splitting has emerged as a hotspot in the domain of photocatalysis. Therefore, we have designed an S-scheme ZnO-TiO2-Ag (Zn-Ti-Ag) catalyst through the hydrothermal process to investigate photocatalytic H2 production under simulated sunlight exposure. The H2 production efficiency of Zn-Ti-Ag catalyst from water/formic acid solution is 60.4 mmolh−1g−1, which is exceptionally greater than that of pure ZnO (0.39 mmolh−1g−1) under identical experimental conditions. After five successive cycles, no obvious decline of photocatalytic activity over Zn-Ti-Ag verifies its outstanding stability for large-scale application. The exceptionally enhanced photocatalytic performance of Zn-Ti-Ag heterojunction can be attributed to efficient photocarriers separation and transport efficiency, improved light absorption resulting from the LSPR effect of Ag, and powerful redox potentials due to the construction of S-scheme. This research provides an efficient orientation to understand and design LSPR phenomenon-assisted oxides-based S-scheme heterojunctions for diverse photocatalytic applications.

In-situ adsorption-conversion recovery of heavy metal cadmium by natural clay mineral for multi-functional photocatalysis

Pollutant purification, waste recycle and efficient utilization of mineral resources are three main subjects in the environmental fields, while it is hard to achieve simultaneously. Here, we developed a sustainable “adsorbent-to-photocatalyst” strategy for recovering Cd2+ into CdS photocatalyst with clay minerals to simultaneously address the above issues. By comparing the adsorption ability of three natural clay minerals, including sepiolite, attapulgite (ATP) and halloysites, ATP is screened out as a cost-effective adsorbent for the removal of heavy metals Cd2+ from waste water, and then serves as a substrate to allow Cd2+ to be converted into CdS nanoparticles in situ on its surface. The as-prepared CdS/ATP composite materials show multi-functional photocatalytic applications, which are effective in removing heavy metals Cr(VI), tetracycline hydrochloride and killing harmful pathogens in water under visible light. It is demonstrated that the excellent adsorption capacity and production of large number of active species (electrons, holes, hydroxyl radicals and superoxide radicals) are the main reasons for the efficient catalytic activity of CdS/ATP. This study provides a novel reference for the development direction of highly efficient integrated design strategy of heavy metals recovery and high-performance photocatalyst fabrication with cost-effective natural clay minerals.

Synthesis of 2D/2D structural Ti3C2 MXene/g-C3N4 via the Schottky junction with metal oxides: Photocatalytic CO2 reduction with a cationic scavenger

A series of Ti3C2/CN/Cu2O and Ti3C2/CN/ZnO ternary nanocomposites were successfully fabricated by the integration of 2D Ti3C2 MXene and 2D polymeric carbon nitride (CN) with ZnO and Cu2O. The HF etching on Ti3C2 MXene offered significant improvement for the photocatalyst fabrication, while the close 2D/2D junction of Ti3C2/CN created the Schottky junction to enable proficient electron transfer in the ternary nanocomposite. Next, the junction of 2D MXene and 2D CN with the metal oxides (Cu2O and ZnO) prevented the quick recombination of photoexcited electrons and holes and contributed multiple electron pathways for the CO2/CH3OH process. At the same time, the formation of analogue Z-scheme heterojunctions through the synergistic effect of 2D Ti3C2 MXene and 2D metal-free CN with ZnO contributed to the rapid separation and transfer of photogenerated charge carriers. As a result, the photocatalytic CO2 reduction activity of Ti3C2/CN/Cu2O and Ti3C2/CN/ZnO ternary nanocomposites was significantly enhanced. Meanwhile, adding a Na2SO3 sacrificial electron donor with pure water and NaHCO3 solvent system supply in CO2 photoreduction experiments contributed to the formation of CH3OH. In particular, the yield of CH3OH was up to 18.72% and 19.98%, 5times and 6-times fold than the pure Cu2O and ZnO, while 3-times fold than the TCCN in a water system. In a NaHCO3 solvent with the sacrificial electron donor, the CH3OH rates over Ti3C2/CN/ZnO and Ti3C2/CN/Cu2O were 22.41% and 20.12%. Taking into account the chemical and structural tunability of ternary nanocomposites, the excellent photocatalytic ability of Ti3C2/CN/ZnO and Ti3C2/CN/Cu2O could be used in the future production of hydrocarbon fuels, as well as increasing the possibility of using 2D MXene in photocatalyst fabrication.

Preparation of βCD‐AC functionalized ZnO/ZnSe for photocatalytic degradation of organic dye wastewater

Conventional photocatalysts for degrading pollutants are limited because of the rapid recombination of electron–hole pair, difficulty in separation and recovery, and low efficiency in utilizing the visible light. To improve the adsorption capacity of the photocatalyst and reduce electron–hole recombination rate, βCD was anchored onto the porous activated carbon (AC) and then combined with ZnO/ZnSe to prepare βCD‐AC‐ZnO/ZnSe. The ZnO was a quasi‐hexahedron shape in the ZnO/ZnSe heterojunction and was tightly integrated with the βCD‐AC, which could improve the transfer ability of the photogenerated carrier. Considering the synergistic effect of βCD‐AC and ZnO/ZnSe, the UV absorption edge was red shifted, and the lifetime of the electrons–hole pairs was prolonged. Thus, the photocatalytic degradation ration of βCD‐AC‐ZnO/ZnSe reached 82% under visible light, which was about 1.8 and 4.2 times higher than those of the virgin heterojunction and AC‐ZnO/ZnSe, respectively. βCD‐AC‐ZnO/ZnSe exhibited excellent disinfection potential that 3.5 log Escherichia coli cells were killed for 120 min. The high‐efficiency visible‐light photocatalytic performance was demonstrated, and the •O2− played a main active role in the photocatalytic removal of pollutants. The present research provided a valuable route for the fabrication of photocatalyst for real‐world applications.

UV light-induced oxygen doping in graphitic carbon nitride with suppressed deep trapping for enhancement in CO2 photoreduction activity

• Oxygen (O) element is introduced in the bulk graphitic carbon nitride (CN) for the first time through a precursor pretreatment by ultraviolet (UV) light irradiation. • The doped O non-metal photocatalyst of CN increased visible light absorption and enhanced carrier density. • The optimized sample has lower charge recombination and suppressed electron deep trapping. • The optimized sample shows enhanced photoreduction activity of CO2 to CH4. While photoreduction of CO 2 to CH 4 is an effective means of producing value-added fuels, common photocatalysts have poor activity and low selectivity in photocatalytic CO 2 -reduction processes. Even though creating defects is an effective photocatalyst fabrication route to improve photocatalytic activity, there are some challenges with the facile photocatalyst synthesis method. In this work, an O element is introduced into a graphitic carbon nitride (CN) skeleton through a precursory ultraviolet light irradiation pretreatment to increase the visible light absorption and enhance the carrier density of this modified non-metal CN photocatalyst; the charge transfer dynamics thereof are also studied through electrochemical tests, photoluminescence spectroscopy, and nanosecond transient absorption. We verify that the optimized sample exhibits lower charge recombination and a suppressed 84 ns electron-trapping lifetime, compared to the 103 ns electron-trapping lifetime of the CN counterpart, and thereby contributes to robust detrapping and a fast transfer of active electrons. Through density functional theory calculations, we find that the improved light absorption and increased electron density are ascribed to O-element doping, which enhances the CO 2 adsorption energy and improves the CO 2 -to-CH 4 photoreduction activity; it becomes 17 times higher than that of the bare CN, and the selectivity is 3.8 times higher than that of CN. Moreover, the optimized sample demonstrates excellent cyclic stability in a 24-hour cycle test.

Recent Developments of Electrospinning-Based Photocatalysts in Degradation of Organic Pollutants: Principles and Strategies.

Electrospinning is a simple and cheap process for forming one-dimensional (1D) nanofibers with controllable size, morphology, and chemistry. Besides these, the ultrahigh surface area with industrialization capability has attracted extensive interest in the research community. On the other hand, a photocatalytic process is a promising method for degrading organic pollutants that cannot be removed by conventional wastewater treatment. This review focuses on the recent progress of electrospun nanofibers for the photocatalytic degradation of water pollutants. The linkage between the electrospinning technique and the photocatalytic process is classified into two main categories: (1) polymeric electrospun nanofibers as a sacrificed template to form 1D photocatalysts and (2) polymeric electrospun nanofibers as a carrier of photocatalyst materials. We have thoroughly discussed the principles and fundamental issues of electrospinning as well as two main strategies to design and fabricate nanofiber-based photocatalysts for the ideal photodegradation of organics pollutants. The results of data mapping using VOSviewer demonstrated the recent trend and the importance of this field among researchers and engineers. Moreover, we have elaborated on the limitations and potential benefits of the two categories of electrospinning-based photocatalyst fabrication and practical application that will open new directions for future research.

Efficient Visible-Light-Driven Hydrogen Production over Cu-Modified Polyoxotungstate Hybrids.

Hydrogen energy is a renewable and clean source, which makes a great difference in future sustainable energy systems. Visible-light-driven photocatalysis reaction involves harnessing the abundance of sunlight for hydrogen production among many catalytic technologies. However, the fabrication of photocatalysts that have distinctive performance in visible light is still the primary challenge. Herein, two new Cu-modified polyoxotungstate hybrids, {[Cu2(bim)4(H2O)2](HBW12O40)2·(H2bim)2·8H2O} (1) (bim = [1,1'-methylenebis(1H-imidazole)]) and {[Cu2(bim)4(H2O)2](H3PW10Ti2O40)2·(H2bim)2·8H2O} (2), have been successfully isolated by bridging two saturated Keggin polyoxotungstates and copper-azole complexes. Not surprisingly, 2 holds higher reduction activity due to the more negative charge and stronger basicity on the terminal oxygen of Ti═O and bridge oxygen of Ti-O-W. The H2 yield was 17075 μmol g-1 h-1 for 2 in the tunable light-driven H2 production system, which is promising in the field of photocatalysis.

Molecular engineering optimized carbon nitride photocatalyst for CO2 reduction to solar fuels

The structural alteration of carbon nitride (CN) for photocatalytic CO 2 reduction is a promising research topic in the environmental and energy sectors. This work discusses the fabrication of photocatalyst through a heterojunction architecture obtained from the molecular engineering of electron-rich organic monomer 2,6-pyridinedicarboxylic acid (PDA) with CN precursor (CN/PDA x ). The successful integration of PDA in the structure of CN served as a charge inducting entity to enhance charge separation and photocatalytic CO 2 reduction under visible light (λ = 420 nm). The DFT results indicated that the upshift in the HOMO level of CN after integration of PDA in its framework was the most lawful for the charge separation and for obtaining a high reduction potential. As-synthesized photocatalysts were demonstrated for various integral analysises and after evaluating the process of photocatalytic CO 2 reduction under visible light region (λ = 420 nm). The optimized sample CN/PDA 10 has the most excellent photocatalytic activity producing 85.4 μmol/h of CO and 21.3 μmol/h of H 2 , achieving a 7.5-fold enhanced catalytic efficiency as compared to pure CN. We hope that this work will attract more attention to synthesizing efficient photocatalysts for energy production and environmental remediation. • Organic monomer 2,6-pyridinedicarboxylic acid (PDA) within CN framework (CN/PDAx). • A copolymerization process occur as a nucleophilic reaction b/w CN/PDAx. • Samples demonstrating remarkable photocatalytic CO 2 reduction under visible light. • The DFT results indicate charge separation for obtaining a high reduction potential. • The optimized sample CN/PDA 10 producing 85.4 μ mole CO and 21.3 μmole H 2 .

Ultrasonic-assisted synthesis of α-Fe2O3@TiO2 photocatalyst: Optimization of effective factors in the fabrication of photocatalyst and removal of non-biodegradable cefixime via response surface methodology-central composite design

Environmental pollution becomes a major worldwide issue that threatens the entire biosphere.On the other hand, visible-light photocatalysis technology is one of the most effective approaches to wastewater treatment due to its superb removal efficiency, facile process, and ecological friendliness.Herein, a highly efficient α-Fe2O3@TiO2 nanocomposite was synthesized using a rapid sonochemical technique and a conventional wet impregnation route for the elimination of cefixime. Towards achieve the optimal photocatalyst, the influences of operational parameters including calcination temperature (300–600 °C), and Fe2O3 loadings (1-5 wt%) were examined utilizing the Response Surface Methodology (RSM). Additionally, two important factors, irradiation time (3–8 min) and power (50–90 W) of ultrasonic waves, were investigated to optimize the efficiency, dimension, and structure of the photocatalyst. Then, the manufactured nanocomposites were characterized with the aid of techniques TEM, XRD, BET, FE-SEM, EDS-map, FTIR, and UV–Vis band gap analysis. The optimal photocatalyst (3.09 wt%, 439.34 °C, 70 W, and 8 min) was used to study the effect of four efficacious variables on cefixime removal by RSM. Maximum cefixime degradation (98.8%) occurred at optimum conditions (cefixime concentration = 20.5 mg/L, pH = 4.76, Irradiation time = 103 min and catalyst dose = 0.012 g/l). Based on the empirical data, statistical analysis proved the regression model's validity and adequacy. The COD elimination revealed that in comparison with other studies the α-Fe2O3@TiO2 photocatalyst could successfully mineralize cefixime (82.4%). Generally, the stability of α-Fe2O3@TiO2 in the photocatalytic degradation of cefixime was observed across five cycles with minimal iron leaching, making it a perfect catalyst for the removal of non-biodegradable pharmaceuticals.

Novel ZnFe2O4/Bi2S3 high-low junctions for boosting tetracycline degradation and Cr(VI) reduction

The fabrication of photocatalysts with high reaction activity for decomposition of pharmaceutical contaminants and detoxication of heavy metal ions in wastewater is challenging. In this study, novel ZnFe2O4/Bi2S3 high-low junctions with different work functions and tight interface were constructed by the growth of Bi2S3 over ZnFe2O4 under hydrothermal conditions, and the content of ZnFe2O4 was optimized. The optimal 12 % ZnFe2O4/Bi2S3 sample exhibited the best visible-light photocatalytic performance of 91.6 % tetracycline removal at solution pH of 4.72 and 96.7 % reduction efficiency of Cr(VI) at solution pH of 5.51 within 2 h. Holes (h+), hydroxyl radicals (OH) and superoxide radicals (O2−) jointly attacked tetracycline, leading to efficacious decomposition of tetracycline and sharp toxicity reduction. The toxicity prediction of degradation intermediates by ECOSAR software and E. coli growth further confirmed the significant role of ZnFe2O4/Bi2S3 high-low junction in toxicity reduction of tetracycline. The photogenerated electrons were involved in Cr(VI) reduction. The relationship between structure and photocatalytic activity was set forth from the view of light absorption, band structure, internal electric field at interface, charge separation and migration behaviors. Importantly, the photocatalytic mechanism of ZnFe2O4/Bi2S3 high-low junctions with different work functions and intimate interface was first provided based on edge energy offset. This work will provide new insights for the preparation and application of high-low junction photocatalytic materials based on CB/VB edge energy shift and unique photogenerated charge transfer mechanism.

Efficient removal of As, Cu and Cd and synthesis of photo-catalyst from Cu-smelting waste acid through sulfide precipitation by biogenic gaseous H2S produced by anaerobic membrane bioreactor

The proper disposal of Cu-smelting waste acid (CSWA) is a major challenge in sulfide ores pyrometallurgy industry due to its high content of H2SO4, extremely high concentration of As and multiple toxic metals. The neutralization precipitation using cheap CaO is the most widely used process in tackling CSWA. However, a large amount of hazardous wastes covering As and other heavy metals which requires further disposal is generated, and the valuable H2SO4 cannot be reused. Herein, anaerobic membrane bioreactor (AnMBR) is used to continuously produce gaseous H2S for sulfide precipitation of the refractory CSWA and simultaneous fabrication of photo-catalyst for the first time. The 200L AnMBR respectively gained the highest total H2S production of 6.41 g/h and the highest gaseous H2S production of 5.05 g/h under the optimal conditions, being 3–9 times higher than previous reports by other types of bioreactors. And the sulfide precipitation triggered by the maximum gaseous H2S of 5.05 g/h harvested almost 100 % removal for Cu, As and Cd from CSWA within a short time from 0.35 to 3.69 days. Moreover, the phase 1 precipitate covering Cu-S compounds displayed an efficient photo-catalytic activity. The sulfide precipitation by AnMBR showed an application potential in tackling the refractory CSWA and fabrication of valuable nanoparticle photo-catalyst.