Fabricated novel g-C3N4/Mn doped ZnO nanocomposite as highly active photocatalyst for the disinfection of pathogens and degradation of the organic pollutants from wastewater under sunlight radiations

Novel yellowish-green single-phased spinel Mg1-xBaxAl2O4:Mn2+ phosphor(s) for color rendering white-light-emitting diodes

For white light-rendering research activities, interpretation by using colored emitting materials is an alternative approach. But there are issues in designing the white color emitting materials. Particularly, differences in thermal and decay properties of discrete red, green, and blue emitting materials led to the quest for the search of a single-phased material, able to emit primary colors for white light generation. The current study is an effort to design a simple, single-phase, and cost-effective material with the tunable emission of primary colors by a series of Mg1-xBaxAl2O4:Mn2+ nanopowders. Doping of manganese ion (Mn2+) in the presence of the larger barium cation (Ba2+) at tetrahedral-sites of the spinel magnesium aluminate (MgAl2O4) structure led to the creation of antisite defects. Doped samples were found to have lower bandgaps compared with MgAl2O4, and hybridization of 3d-orbitals of Mn2+ with O(2p), Mg(2s)/Al(2s3p) was found to be responsible for narrowing the bandgap. The distribution of cations at various sites at random results in a variety of electronic transitions between the valance band and oxygen vacancies as well as electron traps produced the antisite defects. The suggested compositions might be used in white light applications since they have three emission bands with centers at 516 nm (green), 464 nm (blue) and 622 nm (red) at an excitation wavelength of 380 nm. A detailed discussion to analyze the effects of the larger cationic radius of Ba2+ on the lattice strain, unit cell parameters, and cell volumes using X-ray diffraction analysis is presented.

A facile synthesis process of GCN/ZnO-Cu nanocomposite and the evaluation of the performance for the photocatalytic degradation of organic pollutants and the disinfection of wastewater under visible light

In this research, graphitic carbon nitride/zinc oxide-copper denoted as GCN/ZnO-Cu nanocomposite photocatalysts were synthesized using a novel facile synthesis process, the co-exfoliation method involving ultrasonic exfoliation of the mixture of GCN and ZnO-Cu in ethanol and then thermal exfoliation. Different characterization techniques such as X-ray diffraction (XRD), mean crystallite size (MCS), BET surface area, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), particle size distribution (PSD), Fourier transform-infrared spectroscopy (FT-IR), photoluminescence (PL) spectra, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) were conducted to study the crystallinity, morphology, elemental composition, chemical structure, and optoelectronic properties. The band gap was estimated using the UV-Vis DRS results and Tauc plots. The photocatalytic activity of the GCN/ZnO-Cu3% nanocomposites was evaluated in the degradation of 4-chlorophenol (4-CP), and the disinfection of wastewater primary influent under a narrowband visible light source, royal blue LED (λ = 450 nm). GCN/0.1ZnO-Cu3% nanocomposite showed the best performance in the degradation of 4-CP and the disinfection of municipal wastewater primary influent. For 4-CP degradation, GCN/0.1ZnO-Cu3% was 2.2 times better than GCN, 9.4 times better than ZnO-Cu3%, and 1.8 times better than the sum of the individual GCN and ZnO-Cu3%. A 5.5 log reduction was achieved for the disinfection of total coliforms in wastewater primary influent in 360 min. This enhanced photocatalytic activity of GCN/ZnO-Cu3% nanocomposite can be attributed to the synergistic of GCN and the ZnO-Cu3%, resulting in a large surface area and improved bandgap.

Morphological evaluation and boosted photocatalytic activity of N-doped ZnO nanoparticles prepared via Co-precipitation method

Pristine and nitrogen (N) doped zinc oxide (ZnNxO1-x, x = 0, 0.005, 0.01, and 0.02) nanoparticles (NPs) were successfully synthesized using chemical co-precipitation approach. The formation of pure crystalline wurtzite ZnO phase without any second phase during N-doping was confirmed by X-ray diffraction (XRD) analysis of N-doped ZnO samples. X-ray photoelectron spectroscopic (XPS) analysis ensured the effective inclusion of nitrogen into ZnO matrix. The morphological analysis revealed the formation of nanorods as a result of N-doping. The optical band gap calculated from UV-vis spectroscopy was observed to decrease up to 1 mol.% N doping followed by a subtle increase. Photoluminescence (PL) spectra revealed that electron-hole recombination was the least for 1 mol.% N doped ZnO NPs. ZnN0.01O0.99 NPs showed superior photocatalytic activity among all samples due to rod-shaped NPs and reduced electron-hole recombination, which was accessed by the photodegradation of Rhodamine B (RhB).

Hybrid nanostructures exhibiting both photocatalytic and antibacterial activity-a review

The most vital issues of the modern world for a sustainable future are "health" and "the environment." Scientific endeavors to tackle these two major concerns for mankind need serious attention. The photocatalytic activity toward curbing environmental pollution and antibacterial performance toward a healthy society are two directions that have been emphasized for decades. Recently, materials engineering, in their nanodimension, has shown tremendous possibilities to integrate these functionalities within the same materials. In particular, hybrid nanostructures have shown magnificent prospects to combat both crucial challenges. Many researchers are separately engaged in this important field of research but the collective knowledge on this domain which can facilitate them to excel is badly missing. The present article integrates the development of different hybrid nanostructures which exhibit both photocatalytic degradations of environmental pollutants and antibacterial efficiency. Various synthesis techniques of those hybrid nanomaterials have been discussed. Hybrid nanosystems based on several successful materials have been categorically discussed for better insight into the research advancement in this direction. In particular, Ag-based, metal oxides-based, layered carbon material-based, and Mexene- and self-cleaning-based materials have been chosen for detailing their performance as anti-pollutant and antibacterial materials. Those hybrid systems along with some miscellaneous booming nanostructured materials have been discussed comprehensively with their success and limitations toward their bifunctionality as antipollutant and antibacterial agents.

Water remediation using titanium and zinc oxide nanomaterials through disinfection and photo catalysis process: A review

Various pesticides and organic compounds generated as a result of rapid industrialization and pharmaceutical companies pose a major threat to the environment. Novel photocatalysts based on zinc oxide and titanium oxide exhibit great potential towards absorption of these organic pollutants from wastewater. The photocatalysts possess various extraordinary properties like photocatalytic degradation potential, non-toxic and high stability. However, several limitations are also associated with the applications of these photocatalysts like poor affinity, particle agglomeration, high band gap and recovery issues. Hence, optimization is required to enhance their efficiency and at the same time make them cost effective and sustainable. The review covers the mechanism for water treatment, limitations and development of different modification strategies that improve the removal efficiency of titanium and zinc oxide based photocatalysts. Thus, further research in the field of photocatalysts can be encouraged for carrying out water remediation.

g-C3N4-Co3O4 Z-Scheme Junction with Green-Synthesized ZnO Photocatalyst for Efficient Degradation of Methylene Blue in Aqueous Solution

A simple wet chemical ultrasonic-assisted synthesis method was employed to prepare visible light-driven g-C3N4-ZnO-Co3O4 (GZC) heterojunction photocatalysts. X-ray diffraction (XRD), scanning electromicroscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), ultraviolet (UV), and electrochemical impedance spectroscopy (EIS) are used to characterize the prepared catalysts. XRD confirms the homogenous phase formation of g-C3N4, ZnO, and Co3O4, and the heterogeneous phase for the composites. The synthesized ZnO and Co3O4 by using cellulose as a template show a rod-like morphology. The specific surface area of the catalytic samples increases due to the cellulose template. The measurements of the energy band gap of a g-C3N4-ZnO-Co3O4 composite showed red-shifted optical absorption to the visible range. The photoluminescence (PL) intensity decreases due to the formation of heterojunction. The PL quenching and EIS result shows that the reduction of the recombination rate and interfacial resistance result in charge carrier kinetic improvement in the catalyst. The photocatalytic performance in the degradation of MB dye of the GZC-3 composite was about 8.2-, 3.3-, and 2.5-fold more than that of the g-C3N4, g-C3N4-ZnO, and g-C3N4-Co3O4 samples. The Mott-Schottky plots of the flat band edge position of g-C3N4, ZnO, Co3O4, and Z-scheme g-C3N4-ZnO-Co3O4 photocatalysts may be created. Based on the stability experiment, GZC-3 shows greater photocatalytic activity after four recycling cycles. As a result, the GZC composite is environmentally friendly and efficient photocatalyst and has the potential to consider in the treatment of dye-contaminated wastewater.

Synthesis of Mn-Doped ZnO Nanoparticles and Their Application in the Transesterification of Castor Oil

Alarming environmental changes and the threat of natural fuel resource extinction are concerning issues in human development. This has increased scientists’ efforts to phase out traditional energy resources and move on to environmentally friendly biofuels. In this study, non-edible castor oil was transesterified with methanol using a manganese-doped zinc oxide (Mn-doped ZnO) nanocatalyst. A heterogeneous nanocatalyst was prepared by means of the the sonochemical method. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) were used to characterize these nanocatalysts. The transesterification reaction was studied under different temperature conditions, different ratios of methyl alcohol to castor oil, and different amounts of the catalyst to identify optimum conditions in which the maximum yield of biodiesel was produced. The maximum biodiesel yield (90.3%) was observed at 55 °C with an oil-to-methanol ratio of 1:12, and with 1.2 g of nanocatalyst. The first-order kinetic model was found to be the most suitable. Several thermodynamic parameters were also determined, such as activation energy, enthalpy, and entropy. We found that this transesterification was an endergonic and entropy-driven reaction. The results showed that the Mn-doped ZnO nanocatalyst could be a suitable catalyst for the heterogeneous catalytic transesterification process, which is essential for biodiesel production.

Preparation and modification of bagasse biochar unveiling ofloxacin wastewater adsorption

Currently, ofloxacin (OFX) is widely used in various medical treatment and aquaculture industries. However, its production and application produces waste which pollutes the natural environment and causes ecological damage. The application of biochar is a crucial way to remove OFX antibiotics from wastewater. In this paper, bagasse was used as the material to be pyrolyzed to obtain bagasse biochar (BC). BC was modified with HNO3 and KOH to prepare acid-modified sugarcane biochar (HBC) and alkali-modified sugarcane biochar and subsequently applied to the treatment of ofloxacin wastewater. The results showed that the adsorption capacity of HBC was 2.2 times higher than that of BC, and it had better adsorption performance. When the dosage of acid-modified biochar was 1 g/L and the initial pH of the solution was 7.0, the OFX removal rate reached 88.5% after 90 min of reaction. HBC has good stability, and the OFX removal efficiency is still up to 78.5% after 5 cycles. According to the adsorption simulation results, the adsorption of the three biochar materials is more consistent with the Freundlich adsorption model, and the simulated linear correlation coefficient is higher than 0.99. The Kfr value of HBC is 6.6042, which exhibits the highest adsorption capacity. Moreover, the three biochars exhibit better simulation results in pseudo-second-order kinetics fitting, and the linear correlation coefficients are above 0.99. The adsorption mechanism of bagasse biochar for ofloxacin in wastewater was π-π electron donor-acceptor interactions. The results show that bagasse biochar has good feasibility in the treatment of ofloxacin wastewater.

Integration of Mn-ZnFe2O4 with S-g-C3N4 for Boosting Spatial Charge Generation and Separation as an Efficient Photocatalyst

The disposal of dyes and organic matter into water bodies has become a significant source of pollution, posing health risks to humans worldwide. With rising water demands and dwindling supplies, these harmful compounds must be isolated from wastewater and kept out of the aquatic environment. In the research presented here, hydrothermal synthesis of manganese-doped zinc ferrites’ (Mn-ZnFe₂O₄) nanoparticles (NPs) and their nanocomposites (NCs) with sulfur-doped graphitic carbon nitride (Mn-ZnFe₂O₄/S-g-C₃N₄) are described. The samples’ morphological, structural, and bonding features were investigated using SEM, XRD, and FTIR techniques. A two-phase photocatalytic degradation study of (0.5, 1, 3, 5, 7, 9, and 11 wt.%) Mn-doped ZnFe₂O₄ NPs and Mn-ZnFe₂O₄/(10, 30, 50, 60, and 70 wt.%) S-g-C₃N₄ NCs against MB was carried out to find the photocatalyst with maximum efficiency. The 9% Mn-ZnFe₂O₄ NPs and Mn-ZnFe₂O₄/50% S-g-C₃N₄ NCs exhibited the best photocatalyst efficiency in phase one and phased two, respectively. The enhanced photocatalytic activity of the Mn-ZnFe₂O₄/50% S-g-C₃N₄ NCs could be attributed to synergistic interactions at the Mn-ZnFe₂O₄/50% S-g-C₃N₄ NCs interface that resulted in a more effective transfer and separation of photo-induced charges. Therefore, it is efficient, affordable, and ecologically secure to modify ZnFe₂O₄ by doping with Mn and homogenizing with S-g-C₃N₄. As a result, our current research suggests that the synthetic ternary hybrid Mn-ZnFe₂O₄/50% S-g-C₃N₄ NCs may be an effective photocatalytic system for degrading organic pollutants from wastewater.

Visible-light-responsive photocatalytic inactivation of ofloxacin-resistant bacteria by rGO modified g-C3N4

The visible light responsive graphitic nitride (g-C₃N₄) mediated photocatalysis has drawn extensive attention in water treatment field. Carbon doping could improve the photocatalytic activity of g-C₃N₄ in promoting charge separation efficiency, visible-light utilization, etc. In this paper, the g-C₃N₄ (as MC) was modified by barbituric acid (as MCB_0.07) and further treated by reduced graphene oxide (rGO) (as n%GCN) and then applied to inactivate ofloxacin-resistant bacteria (OFLA) under light irradiation at UVA-visible wavelength. The results showed that the n%GCN presented strong photocatalytic activity when the GO mass ratio was 7.5% (as 7.5%GCN). The inactivation efficiencies of OFLA by MC, MCB_0.07, and 7.5%GCN were 5.77 log, 8.48 log, and 8.25 log, respectively, under UVA-visible wavelength (λ > 305 nm), compared to 4.83 log, 5.56 log, and 6.08 log, respectively, within 16 h under visible wavelength (λ > 400 nm). The rGO-doping obviously improved the inactivation efficiency of MCB_0.07 on OFLA under visible wavelength. Furthermore, the photoreactivation and dark repair phenomena of OFLA were examined after MC, MCB_0.07, and 7.5%GCN treatment, respectively, and it was found that all approaches led to permanent damage to OFLA of which the regrowth was not observed after 24-48 h. Based on the quenching test, reactive oxygen species of O₂^-• and hole (h⁺) exhibited dominant roles in the photocatalytic inactivation of OFLA, which may result in oxidative stress and damage to the cell membrane. This study could shed light on the inactivation of OFLA under visible light radiation by rGO modified g-C₃N₄.

Boosted spatial charge carrier separation of binary ZnFe2O4/S-g-C3N4 heterojunction for visible-light-driven photocatalytic activity and antimicrobial performance

A potential method for removing toxins from contaminated wastewater, especially organic pollutants, is photo-catalysis. Here, a simple technique for producing zinc ferrite nanoparticles (ZnFe2O4 NPS) with varying quantities of sulphur doped graphitic carbon nitride nanocomposites (ZnFe2O4/S-g-C3N4 NCs) has been described. Then, using X-ray diffraction (XRD), TEM, EDX, XPS, photocurrent response, EIS, and Fourier Transform Infrared spectroscopy (FT-IR), the photo-catalytic activity of the produced nanoparticles (NPs) and nanocomposites (NCs) was examined and evaluated. The photo-catalytic activity of ZnFe2O4/S-g-C3N4 NCs was compared to a model pollutant dye, methylene blue, while degradation was evaluated spectrophotometrically (MB). Solar light has been used through irradiation as a source of lighting. The photocatalytic behaviour of the ZnFe2O4/S-g-C3N4 NCs photocatalyst was superior to that of genuine ZnFe2O4 and S-g-C3N4, which was attributed to synergic effects at the ZnFe2O4/S-g-C3N4 interconnection. Antimicrobial activity of ZnFe2O4/S-g-C3N4 against Gram-positive and Gram-negative bacteria under visible light was performed. In addition, these ZnFe2O4/S-g-C3N4 NCs show a lot of promise as an antibacterial agent.

Ag/polydopamine-coated textile for enhanced liquid/liquid mixtures separation and dye removal

Engineering a versatile platform that enables to separate both oil/water and oil/oil mixtures and remove dye from water is not easy. To address this challenge, we have developed an Ag/polydopamine-coated textile (Ag/PDA@textile) by chemically depositing Ag particles on the textile surface using polydopamine as the binder layer. The obtained Ag/PDA@textile attracts water but repels oil in the air, underwater, and when immersed into the oil. Exploiting its water-attracting and oil resistance, the Ag/PDA@textile is acted as a separation membrane to separate oil/water mixtures with enhanced separation efficiency. The Ag/PDA@textile also possesses opposite wetting behavior to oils with different polarities, allowing it to separate oil/oil mixtures efficiently. Thanks to the catalytic performance of the Ag particle, organic dyes can be decomposed effectively by our Ag/PDA@textile under UV illustration or in the presence of NaBH₄. Our Ag/PDA@textile may be valuable for applications in water purification and oil sewage treatment.

Viscosity Simulation of Glass Microfiber and an Unusual Air Filter with High-Efficiency Antibacterial Functionality Enabled by ZnO/Graphene-Modified Glass Microfiber

The current global pandemic of new coronary pneumonia clearly reveals the importance of developing highly efficient filtration and fast germicidal performance of multifunctional air filters. In this study, a novel air filter with a controllable morphology based on the rod-like to flower-like zinc oxide/graphene-based photocatalytic composite particles loaded on glass microfiber was prepared by one-step microwave rapid synthesis. The multifunctional air filter shows the following special functions: the 10 mg·L^-1 organic pollutant solution RhB was completely degraded within 2 h under a 500 W xenon lamp, and also 99% of Escherichia coli and Staphylococcus aureus were inactivated under a 60 W light-emitting diode lamp. Furthermore, after introducing the controllable morphology zinc oxide/graphene-based photocatalytic composite particles, the filtration efficiency of the multifunctional air filter was also kept at the same level (99.8%) as the one without any addition, indicating no loss of high-efficiency filtration while obtaining the rapid bactericidal function. The rapid antibacterial principle of the multifunctional air filter has also been proposed through the UV-vis spectroscopies, photoluminescence, and electron-spin resonance spectrum. The zinc oxide/graphene-based photocatalytic composite particles tightly coated on the glass microfiber surface could increase the active sites by changing the morphology of zinc oxide and, in the meantime, promote the separation of zinc oxide photo-generated electron-hole pairs to improve the rapid sterilization ability of the multifunctional air filters. In addition, an empirical formula to evaluate the relationship between the composition, viscosity, and viscosity modulus of glass microfiber was proposed by testing the viscosity of glass microfiber composed of 14 different compositions at 1300 and 1400 °C, which can be used as a criterion to evaluate the production technology of glass microfiber filters.

Electro-Oxidation of Metal Oxide-Fabricated Graphitic Carbon Nitride for Hydrogen Production via Water Splitting

Hydrogen is a great sourcez of energy due to having zero emission of carbon-based contents. It is found primarily in water, which is abundant and renewable. For electrochemical splitting of water molecules, it is necessary to use catalytic materials that minimize energy consumption. As a famous carbon material, graphitic carbon nitride, with its excellent physicochemical properties and diversified functionalities, presents great potential in electrocatalytic sensing. In the present work, graphitic carbon nitride-fabricated metal tungstate nanocomposites are synthesized by the hydrothermal method to study their applications in catalysis, electrochemical sensing, and water splitting for hydrogen production. Nanocomposites using different metals, such as cobalt, manganese, strontium, tin, and nickel, were used as a precursor are synthesized via the hydrothermal process. The synthesized materials (g-C3N4/NiWO4, g-C3N4/MnWO4, g-C3N4/CoWO4, g-C3N4/SnWO4, g-C3N4/SrWO4) were characterized using different techniques, such as FTIR and XRD. The presence of a functional groups between the metal and tungstate groups was confirmed by the FTIR spectra. All the nanocomposites show a tungstate peak at 600 cm−1, while the vibrational absorption bands for metals appear in the range of 400–600 cm−1. X-ray diffraction (XRD) shows that the characteristic peaks matched with the JCPDS in the literature, which confirmed the successful formation of all nanocomposites. The electrochemical active surface area is calculated by taking cyclic voltammograms of the potassium–ferrocyanide redox couple. Among the entire series of metal tungstate, the g-C3N4/NiWO4 has a large surface area owing to the high conductive properties towards water oxidation. In order to study the electrocatalytic activity of the as-synthesized materials, electrochemical water splitting is performed by cyclic voltammetry in alkaline medium. All the synthesized materials proved to be efficient catalysts with enhanced conductive properties towards water oxidation. Among the entire series, g-C3N4-NiWO4 is a very efficient electrocatalyst owing to its higher active surface area and conductive activity. The order of electrocatalytic sensing of the different composites is: g-C3N4-NiWO4 > g-C3N4-SrWO4 > g-C3N4-CoWO4 > g-C3N4-SnWO4 > g-C3N4-MnWO4. Studies on electrochemically synthesized electrocatalysts revealed their catalytic activity, indicating their potential as electrode materials for direct hydrogen evolution for power generation.

Cobalt ferrite-modified sol-gel synthesized ZnO nanoplatelets for fast and bearable visible light remediation of ciprofloxacin in water

Currently, metal oxide photocatalysts is a green and facile tool for the elimination of emerging pollutants utilizing light illumination. Though, the wide bandgap energy (E_g), rapid recombination of photogenerated carriers, and photostability of these oxides represent critical issues before the actual application. Herein, we familiarise a sol-gel based synthesis of ZnO hexagonal nanoplatelets modified with CoFe₂O₄ (CFO) nanoparticles at minor loading (1.0-4.0 wt %) to yield CFO/ZnO nanoheterojunctions. The CFO/ZnO unveiled mesostructured surfaces at surface areas of 102-120 m² g^-1 and photoactive in the visible region with high. The CFO addition to ZnO reduced its E_g from 3.14 to 2.66 eV. The formed nanoheterojunctions were applied to remediate ciprofloxacin (CPF), as an antibiotic pollutant in wastewater. The 2.4 g L^-1 3.0 wt % CFO-added ZnO exhibited a 100% removal of 10-ppm CPF within 45 min of visible-light irradiation and sustainable recycling ability for five consecutive runs at 97%. The sustainable performance of CFO/ZnO is ascribed to the suppression of photogenerated carriers and reduction of E by p-n nanoheterojunction formation. This study broadens the way for nanoheterojunction oxides for the destruction of pharmaceutical wastes under visible-light illumination.

Structural, optical and photocatalytic properties of magnetic recoverable Mn0.6Zn0.4Fe2O4@Zn0.9Mn0.1O heterojunction prepared from waste Mn-Zn batteries

Green, simple and high value-adding technology is crucial for realizing waste batteries recycling. In this work, the magnetically recyclable Mn_0.6Zn_0.4Fe₂O₄@Zn_0.9Mn_0.1O (MZFO@ZMO) heterojunctions are prepared from waste Mn-Zn batteries via a green bioleaching and sample co-precipitation method. The as-prepared catalysts with different Zn_0.9Mn_0.1O weight percentage (25%, 50% and 75%) have been comprehensively characterized in structure, optics, photoelectrochemistry and photocatalytic activity. Characterization results indicate that MZFO@ZMO heterojunctions with the core-shell structure, demonstrates excellent absorption intensity in the visible light region, outperforming that of individual ZnO and Zn_0.9Mn_0.1O. Especially, the staggered bandgap alignment of Mn_0.6Zn_0.4Fe₂O₄ and Zn_0.9Mn_0.1O greatly enhances electron transfer and charge separation in the binary heterojunction system. The optimized MZFO@50%-ZMO shows the highest photodegradation performance toward methylene blue (MB) under the visible light irradiation, with a 99.7% of photodegradation efficiency of 20 mg L^-1 of MB within 90 min, and its reactive kinetic constants is about 7.2, 10.8 and 21.7 times higher than that of Zn_0.9Mn_0.1O, P25 TiO₂ and Mn_0.6Zn_0.4Fe₂O₄, respectively. The MB photocatalytic mechanism is investigated in the scavenger and 5,5-dimethylpyrroline-N-oxide (DMPO) spin-trapping electron spin resonance (ESR) experiments, and h⁺ and *O₂^- are identified as the major active species for MB degradation. In addition, MZFO@50%-ZMO also exhibits a good reusability and high magnetic separation properties after six successive cycles. This new material indicates the advantages of low costs, simple reuse and great potential in application.

Recent advances in photocatalytic remediation of emerging organic pollutants using semiconducting metal oxides: an overview

Many untreated and partly treated wastewater from the home and commercial resources is being discharged into the aquatic environment these days, which contains numerous unknown and complex natural and inorganic compounds. These compounds tend to persist, initiating severe environmental problems, which affect human health. Conventionally, physicochemical treatment methods were adopted to remove such complex organic chemicals, but they suffer from critical limitations. Over time, photocatalysis, an advanced oxidation process, has gained its position for its efficient and fair performance against emerging organic pollutant decontamination. Typically, photocatalysis is a green technology to decompose organics under UV/visible light at ambient conditions. Semiconducting nanometal oxides have emerged as pioneering photocatalysts because of large active surface sites, flexible oxidation states, various morphologies, and easy preparation. The current review presents an overview of emerging organic pollutants and their effects, advanced oxidation processes, photocatalytic mechanism, types of photocatalysts, photocatalyst support materials, and methods for improving photodegradation efficiency on the degradation of complex emerging organic pollutants. In addition, the recent reports of metal-oxide-driven photocatalytic remediation of emerging organic pollutants are presented in brief. This review is anticipated to reach a broader scientific community to understand the first principles of photocatalysis and review the recent advancements in this field.

Optimization of photocatalytic degradation conditions and toxicity assessment of norfloxacin under visible light by new lamellar structure magnetic ZnO/g-C3N4

Degradation of norfloxacin (NFX) by zinc oxide (ZnO)/g-C₃N₄, a magnetic sheet ZnO with g-C₃N₄ on its surface was studied. Through a new preparation system method, hydrothermal reaction provides a solid-layered magnetic ZnO material basis, and the simple thermal condensation method was used to transform the urea into g-C₃N₄ on the magnetic sheet ZnO in a uniform and orderly manner to increase the stability and photocatalytic performance of the material. Compared with previous studies, the pore volume and photocatalytic performance of the material are improved, and became more stable. By studying the degradation effect of basic and photocatalytic materials prepared in different proportions, the kinetic constant of ZGF is 0.01446 (min^-1). The response surface methodology (RSM) was used to study the optimization and effect of solution pH (4-12), photocatalyst concentration (0.2-1.8 g/L), and NFX concentration (3-15 mg/L) on the degradation rate of NFX during photocatalytic degradation. The R² value of the RSM model was 0.9656. The NFX removal rate is higher than 90% when the amount of catalyst is 1.43 g/L, the solution pH is 7.12, and the NFX concentration is less than 8.61 mg/L. After 5 cycles, the degradation rate of magnetic materials decreased to 92.8% of the first time. The capture experiment showed that the photocatalytic machine Toxicities was mainly hole action. The TOC removal rate within 2 h was 30%, a special intermediate toxicity analysis method was adopted according to the characteristics of NFX's inhibitory effect on Escherichia coli community. The toxicity of degraded NFX solution disappeared, and the possibility of non-toxic harm of by-products was verified. LC-Q-TOF method was used to detect and analyze various intermediate products converted from NFX after photocatalytic degradation, and the photocatalytic degradation pathway of NFX was proposed.

Designing a novel visible-light-driven heterostructure Ni-ZnO/S-g-C3N4 photocatalyst for coloured pollutant degradation

In this study, photocorrosion of ZnO is inhibited by doping Ni in the ZnO nanostructure and electron-hole recombination was solved by forming a heterostructure with S-g-C3N4. Ni is doped into ZnO NPs from 0 to 10% (w/w). Among the Ni-decorated ZnO NPs, 4% Ni-doped ZnO NPs (4NZO) showed the best performance. So, 4% Ni-ZnO was used to form heterostructure NCs with S-g-C3N4. NZO NPs were formed by the wet co-precipitation route by varying the weight percentage of Ni (0-10% w/w). Methylene blue (MB) was used as a model dye for photocatalytic studies. For the preparation of the 4NZO-x-SCN nanocomposite, 4NZO NPs were formed in situ in the presence of various concentrations of S-g-C3N4 (10-50% (w/w)) by using the coprecipitation route. The electron spin resonance (ESR) and radical scavenger studies showed that O2 - and OH free radicals were the main reactive species that were responsible for MB photodegradation.

Recent advances in graphite carbon nitride-based nanocomposites: structure, antibacterial properties and synergies

Bacterial infections and transmission threaten human health and well-being. Graphite carbon nitride (g-C₃N₄), a promising photocatalytic antibacterial nanomaterial, has attracted increasing attention to combat bacterial transmission, due to the outstanding stability, high efficiency and environmental sustainability of this material. However, the antibacterial efficiency of g-C₃N₄ is affected by several factors, including its specific surface area, rapid electron/hole recombination processes and optical absorption properties. To improve the efficiency of the antibacterial properties of g-C₃N₄ and extend its range of applications, various nanocomposites have been prepared and evaluated. In this review, the advances in amplifying the photocatalytic antibacterial efficiency of g-C₃N₄-based nanocomposites is discussed, including different topologies, noble metal decoration, non-noble metal doping and heterojunction construction. The enhancement mechanisms and synergistic effects in g-C₃N₄-based nanocomposites are highlighted. The remaining challenges and future perspectives of antibacterial g-C₃N₄-based nanocomposites are also discussed.

Photocatalytic Degradation of Methylene Blue Using Zinc Oxide Nanorods Grown on Activated Carbon Fibers

In this work, the synthesis, characterization, and photocatalytic performance of zinc oxide/activated carbon fiber nanocomposites prepared by hydrothermal method were investigated. Zinc oxide nanoparticles (ZnO-NP) were deposited as seeds on porous activated carbon fiber (ACF) substrates. Then, zinc oxide nanorods (ZnO-NR) were successfully grown on the seeds and assembled on the fibers’ surface in various patterns to form ZnO-NR/ACF nanocomposites. The nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, UV–vis diffuse reflectance spectra (DRS), and Brunauer–Emmett–Teller (BET) surface area analysis. SEM images showed that brush-like and flower-like ZnO-NR patterns were grown uniformly on the ACF surface with sizes depending on the ZnO-NP concentration, growth time, and temperature. The FTIR spectrum confirmed the presence of the major vibration bands, especially the absorption peaks representing the vibration modes of the COOH (C = O and C = C) functional group. Adsorption and photocatalytic activities of the synthesized catalytic adsorbents were compared using methylene blue (MB) as the model pollutant under UV irradiation. ZnO-NR/ACF nanocomposites showed excellent photocatalytic activity (~99% degradation of MB in 2 h) compared with that of bare ZnO-NR and ACF. Additionally, a recycling experiment demonstrated the stability of the catalyst; the catalytic degradation ratio of ZnO-NR/ACF reached more than 90% after five successive runs and possessed strong adsorption capacity and high photocatalytic ability. The enhanced photocatalytic activities may be related to the effects of the relatively high surface area, enhanced UV-light absorption, and decrease of charge carrier recombination resulting from the synergetic adsorption–photocatalytic degradation effect of ZnO and ACF.