Review on various strategies for enhancing photocatalytic activity of graphene based nanocomposites for water purification

Highly efficient UV/H2O2 technology for the removal of nifedipine antibiotics: Kinetics, co-existing anions and degradation pathways

This study investigates the degradation of nifedipine (NIF) by using a novel and highly efficient ultraviolet light combined with hydrogen peroxide (UV/H2O2). The degradation rate and degradation kinetics of NIF first increased and then remained constant as the H2O2 dose increased, and the quasi-percolation threshold was an H2O2 dose of 0.378 mmol/L. An increase in the initial pH and divalent anions (SO42- and CO32-) resulted in a linear decrease of NIF (the R2 of the initial pH, SO42- and CO32- was 0.6884, 0.9939 and 0.8589, respectively). The effect of monovalent anions was complex; Cl- and NO3- had opposite effects: low Cl- or high NO3- promoted degradation, and high Cl- or low NO3- inhibited the degradation of NIF. The degradation rate and kinetics constant of NIF via UV/H2O2 were 99.94% and 1.45569 min-1, respectively, and the NIF concentration = 5 mg/L, pH = 7, the H2O2 dose = 0.52 mmol/L, T = 20 ℃ and the reaction time = 5 min. The ·OH was the primary key reactive oxygen species (ROS) and ·O2- was the secondary key ROS. There were 11 intermediate products (P345, P329, P329-2, P315, P301, P274, P271, P241, P200, P181 and P158) and 2 degradation pathways (dehydrogenation of NIF → P345 → P274 and dehydration of NIF → P329 → P315).

Enhanced Visible-Light Absorption of Fe2O3 Covered by Activated Carbon for Multifunctional Purposes: Tuning the Structural, Electronic, Optical, and Magnetic Properties

Visible-light absorption is a critical factor for photocatalyst activity and absorption of electromagnetic (EM) interference application. The band gap of Fe2O3 is 2 eV, which can be increased by doping with a high-band-gap material such as carbon from activated carbon (AC) with a band gap of 4.5 eV for increased visible-light absorption. The porosity decreases from 88 to 81.6%, and the band gap increases from 2.14 to 2.64 eV by increasing the AC from 10 to 25%, respectively. The photocatalytic activity takes 120 min to produce a harmless product for 10-20% AC, but 25% AC shows 89.5% degradation in only 90 min and the potential to attenuate the EM wave up to 99% due to the RL being below -20 dB. The second- and third-cycle degradation achieved by the composite Fe2O3-AC having 25% AC is 88.2 and 86.5% in 90 min, respectively. The pore of the surface state of AC contains a trapped charge, and interaction occurs between the charge (electron/hole) and O2 or H2O to produce OH and superoxide (O2 -) radicals. These radicals move inside the molecule of the pollutant (methylene blue (MB)) to break up the bond, with the final products being H2O and CO2. The X-ray photoelectron (XPS) spectra show that oxygen plays a key role in the interatomic bonding with Fe, C, and MB atoms. The best absorption of EM interference is -21.43 dB, with degradation reaching 89.51% in only 90 min for 25% AC due to its higher band gap and anisotropy constant. Fe2O3-carbon is a multifunctional material for the green environment because of its electromagnetic interference absorption and photodegradation of wastewater.

Advances in the Application of Nanocatalysts in Photocatalytic Processes for the Treatment of Food Dyes: A Review

The use of food additives (such as dyes, which improve the appearance of the products) has become more prominent, due to the rapid population growth and the increase in demand for beverages and processed foods. The dyes are usually found in effluents that are discharged into the environment without previous treatment; this promotes mass contamination and alters the aquatic environment. In recent years, advanced oxidation processes (AOPs) have proven to be effective technologies used for wastewater treatment through the destruction of the total organic content of toxic contaminants, including food dyes. Studies have shown that the introduction of catalysts in AOPs improve treatment efficiency (i.e., complete decomposition without secondary contamination). The present review offers a quick reference for researchers, regarding the treatment of wastewater containing food dyes and the different types of AOPs, with different catalyst and nanocatalyst materials obtained from traditional and green chemical syntheses.

Antibacterial Potential of Zinc Oxide Nanoparticles Synthesized using Aloe vera (L.) Burm.f.: A Green Approach to Combat Drug Resistance

Microbial infections and antibiotic resistance are some of the prime factors that are ascribed to endanger human health. Several reports have highlighted that drug-resistant pathogens assist in the etiology of various chronic diseases and lead to fatality. The present study deciphered the role of zinc oxide nanoparticles (ZnO NPs) as therapeutics against selected bacterial strains. The plant-based technique was followed to synthesize ZnO NPs. The synthesis was confirmed with different techniques viz. X-ray diffraction, transmission electron microscope (interplanar spacing at 0.126 nm), scanning electron microscope (flower-like structure), and Fourier transform infrared spectroscopy. The antibacterial analysis revealed that ZnO NPs inhibited the growth of all tested strains (Escherichia coli, Staphylococcus aureus, Salmonella typhi, Bacillus subtilis, and Klebsiella pneumoniae) to a greater extent (MIC ranged between 0.013±0.004-0.0625±0 mg/mL) as compared with ZnO compound (Bulk material). In the present study, ZnO NPs were produced in a cost-effective and environmentally sustainable way using a green process and can be used as a remedy for drug-resistant pathogens.

Synthesis, Characterization, and Photocatalytic Activities of Graphene Oxide/metal Oxides Nanocomposites: A Review

Sustainable water processing techniques have been extensively investigated and are capable of improving water quality. Among the techniques, photocatalytic technology has shown great potential in recent years as a low cost, environmentally friendly and sustainable technology. However, the major challenge in the industrial development of photocatalyst technology is to develop an ideal photocatalyst which must have high photocatalytic activity, a large specific surface area, harvest sunlight and shows recyclability. Keeping these views, the present review highlighted the synthesis approaches of graphene/metal oxide nanocomposite, characterization techniques and their prominent applications in photocatalysis. Various parameters such as photocatalyst loading, structure of photocatalyst, temperature, pH, effect of oxidizing species and wavelength of light were addressed which could affect the rate of degradation. Moreover, the formation of intermediates during photo-oxidation of organic pollutants using these photocatalysts is also discussed. The analysis concluded with a synopsis of the importance of graphene-based materials in pollutant removal. Finally, a brief overview of the problems and future approaches in the field is also presented.

Recent advances in bismuth oxyhalide photocatalysts for degradation of organic pollutants in wastewater

Photocatalysis has been considered as an environmental-friendly strategy for degradation of organic pollutants to the nontoxic products of H2O and CO2. Compared to metal oxide semiconductors, BiOX (X = Cl, Br and I) photocatalysts exhibit some advantages, such as, unique layered structure, good chemical stability and superior photocatalytic activity. This review provides an overview on the controllable synthesis of BiOX-based photocatalysts and their application in photodegradation of organic pollutants. Firstly, the controllable synthesis of BiOX is introduced, including hydrothermal, solvothermal, hydrolysis, precipitation, two-phase methods, ultrasonic/microwave-assisted methods, and physical methods. Then, the doping and surface modification of BiOX are summarized, including non-metal doping, metal doping, dual doping, and the modification by introducing surface terminations or carriers. In addition, the heterojunctions of BiOX/BiOY and BiOX/Bi m O n X z are introduced. At last, the promising research trends of BiOX-based photocatalysts are put forward. The main purpose is providing practical guidelines for developing high-performance BiOX photocatalysts.

Degradation of primary nanoplastics by photocatalysis using different anodized TiO2 structures

In recent years, plastic pollution has become an environmental problem requiring urgent attention. Recently, the release of nano-sized plastics (<1 µm) into the environment has raised concern due to the possible adverse effects that their small size can have on the trophic web. Advanced oxidation processes are efficient at removing organic pollutants such as dyes and pharmaceuticals, making them a viable approach for treating these hazardous materials. This study proposes the use of photocatalysis as an alternative for removing polystyrene nanoparticles (PS-NPs) from aqueous media. A comparative study was carried out to determine the photocatalytic activity of three different TiO₂ photocatalysts synthesized by anodization. Elimination and degradation were monitored by turbidimetry, TOC, FTIR, and GC/MS, and the presence of carbonyl groups and intermediate products was recorded to confirm PS-NP degradation. Statistical analysis revealed that PS-NP elimination using TiO₂/T and TiO₂/M as photocatalysts was more efficient than with photolysis. The results indicate that the mixed structure (nanotubes/nanograss) reduces the concentration of PS-NPs in dispersion 2 times more efficiently than photolysis with UV light does. Despite the challenges posed by nanoplastic contamination, this study provides a useful remediation approach; a technique that, to date, has received little attention.

Recent Advances in Metal-Organic Frameworks Derived Nanocomposites for Photocatalytic Applications in Energy and Environment

Solar energy is a key sustainable energy resource, and materials with optimal properties are essential for efficient solar energy-driven applications in photocatalysis. Metal-organic frameworks (MOFs) are excellent platforms to generate different nanocomposites comprising metals, oxides, chalcogenides, phosphides, or carbides embedded in porous carbon matrix. These MOF derived nanocomposites offer symbiosis of properties like high crystallinities, inherited morphologies, controllable dimensions, and tunable textural properties. Particularly, adjustable energy band positions achieved by in situ tailored self/external doping and controllable surface functionalities make these nanocomposites promising photocatalysts. Despite some progress in this field, fundamental questions remain to be addressed to further understand the relationship between the structures, properties, and photocatalytic performance of nanocomposites. In this review, different synthesis approaches including self-template and external-template methods to produce MOF derived nanocomposites with various dimensions (0D, 1D, 2D, or 3D), morphologies, chemical compositions, energy bandgaps, and surface functionalities are comprehensively summarized and analyzed. The state-of-the-art progress in the applications of MOF derived nanocomposites in photocatalytic water splitting for H2 generation, photodegradation of organic pollutants, and photocatalytic CO2 reduction are systemically reviewed. The relationships between the nanocomposite properties and their photocatalytic performance are highlighted, and the perspectives of MOF derived nanocomposites for photocatalytic applications are also discussed.

WO3 nanoplates decorated with polyaniline and CdS nanoparticles as a new photocatalyst for degradation of imidacloprid pesticide from water

This study focused on the photocatalytic degradation of imidacloprid (IM) in water as the model pesticides. The effective division of photogenerated charge carriers is important in the photocatalytic reactions. So, a new PANI/WO₃-CdS photocatalyst was synthesized by a simple method. The prepared PANI/WO₃-CdS nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy compatible with energy dispersive spectroscopy (FESEM-EDS), and X-ray diffraction (XRD). Degradation of IM pesticide under visible light irradiation was carried out to investigate the photocatalytic efficiency of the prepared nanocomposite. The effect of operational parameters on the degradation performance of pesticides was studied by response surface methodology (RSM). The optimum conditions for photocatalytic degradation of IM (94.7%) were found to be 10 ppm of IM, 150 mg of PANI/WO₃-CdS, and pH = 3.0. The apparent rate constant of IM photodegradation over PANI/WO₃-CdS was 0.016 min^-1. According to results, PANI/WO₃-CdS can serve as an efficient, and recyclable photocatalyst for imidacloprid degradation in an aqueous media.

WO3 nanoplates decorated with polyaniline and CdS nanoparticles as a new photocatalyst for degradation of imidacloprid pesticide from water

This study focused on the photocatalytic degradation of imidacloprid (IM) in water as the model pesticides. The effective division of photogenerated charge carriers is important in the photocatalytic reactions. So, a new PANI/WO₃-CdS photocatalyst was synthesized by a simple method. The prepared PANI/WO₃-CdS nanocomposite was characterized using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy compatible with energy dispersive spectroscopy (FESEM-EDS), and X-ray diffraction (XRD). Degradation of IM pesticide under visible light irradiation was carried out to investigate the photocatalytic efficiency of the prepared nanocomposite. The effect of operational parameters on the degradation performance of pesticides was studied by response surface methodology (RSM). The optimum conditions for photocatalytic degradation of IM (94.7%) were found to be 10 ppm of IM, 150 mg of PANI/WO₃-CdS, and pH = 3.0. The apparent rate constant of IM photodegradation over PANI/WO₃-CdS was 0.016 min^-1. According to results, PANI/WO₃-CdS can serve as an efficient, and recyclable photocatalyst for imidacloprid degradation in an aqueous media.

Degradation of Harmful Organics Using Visible Light Driven N-TiO₂/rGO Nanocomposite

Nitrogen doped titania over reduced form of graphene oxide (N-TiO₂/rGO) catalysts were synthesized by adopting single step hydrothermal route. All the prepared photocatalysts were thoroughly characterized by using different analytical tools such as XRD, Raman, UV-DRS, FE-SEM and HRTEM. The photocatalytic activities of bare and composite catalysts were evaluated towards the photocatalytic decolourisation/degradation of Methylene blue dye (MB) and Metronidazole antibiotic (MTZ) under visible electromagnetic radiation. Among all the synthesized catalysts, N-TiO₂/rGO composite catalyst showed the highest decolourisation/degradation activity towards both the dye and the antibiotic. The most active catalyst was also tested under UV and solar light irradiations which showed promising results. The stability of the most active catalyst (N-TiO₂/rGO) was examined by recyclability test. The possible photocatalytic mechanism was proposed for the composite catalyst.

Manipulating the Structure and Characterization of Sr1−xLaxTiO3 Nanocubes toward the Photodegradation of 2-Naphthol under Artificial Solar Light

Effective La-doped SrTiO3 (Sr1−xLaxTiO3, x = 0–0.1 mol.% La-doped) nanocubes were successfully synthesized by a hydrothermal method. The influence of different La dopant concentrations on the physicochemical properties of the host structure of SrTiO3 was fully characterized. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) revealed that the Sr2+ in the crystal lattice of SrTiO3 was substituted by La3+. As a result, the absorption region of the Sr1−xLaxTiO3 could be extended to visible light. Scanning electron microscopy (SEM) images confirmed that their morphologies are associated with an increased surface area and an increased La-doping concentration. The decrease in the photoluminescence (PL) intensity of the dopant samples showed more defect levels created by the dopant La+3 cations in the SrTiO3 structure. The photocatalytic activities of Sr1−xLaxTiO3 were evaluated with regard to the degradation of 2-naphthol at typical conditions under artificial solar light. Among the candidates, Sr0.95La0.05TiO3 exhibited the highest photocatalytic performance for the degradation of 2-naphthol, which reached 92% degradation efficiency, corresponding to a 0.0196 min−1 degradation rate constant, within 180 minutes of irradiation. Manipulating the structure of Sr1−xLaxTiO3 nanocubes could produce a more effective and stable degradation efficiency than their parent compound, SrTiO3. The parameters remarkably influence the Sr1−xLaxTiO3 nanocubes’ structure, and their degradation efficiencies were also studied. Undoubtedly, substantial breakthroughs of Sr1−xLaxTiO3 nanocube photocatalysts toward the treatment of organic contaminants from industrial wastewater are expected shortly.

An Overview of the Recent Progress in Polymeric Carbon Nitride Based Photocatalysis

Recently, polymeric carbon nitride (g-C₃ N₄ ) as a proficient photo-catalyst has been effectively employed in photocatalysis for energy conversion, storage, and pollutants degradation due to its low cost, robustness, and environmentally friendly nature. The critical review summarized the recent development, fundamentals, nanostructures design, advantages, and challenges of g-C₃ N₄ (CN), as potential future photoactive material. The review also discusses the latest information on the improvement of CN-based heterojunctions including Type-II, Z-scheme, metal/CN Schottky junctions, noble metal@CN, graphene@CN, carbon nanotubes (CNTs)@CN, metal-organic frameworks (MOFs)/CN, layered double hydroxides (LDH)/CN heterojunctions and CN-based heterostructures for H₂ production from H₂ O, CO₂ conversion and pollutants degradation in detail. The optical absorption, electronic behavior, charge separation and transfer, and bandgap alignment of CN-based heterojunctions are discussed elaborately. The correlations between CN-based heterostructures and photocatalytic activities are described excessively. Besides, the prospects of CN-based heterostructures for energy production, storage, and pollutants degradation are discussed.

Bismuth-Graphene Nanohybrids: Synthesis, Reaction Mechanisms, and Photocatalytic Applications—A Review

Photocatalysis is a classical solution to energy conversion and environmental pollution control problems. In photocatalysis, the development and exploration of new visible light catalysts and their synthesis and modification strategies are crucial. It is also essential to understand the mechanism of these reactions in the various reaction media. Recently, bismuth and graphene’s unique geometrical and electronic properties have attracted considerable attention in photocatalysis. This review summarizes bismuth-graphene nanohybrids’ synthetic processes with various design considerations, fundamental mechanisms of action, heterogeneous photocatalysis, benefits, and challenges. Some key applications in energy conversion and environmental pollution control are discussed, such as CO2 reduction, water splitting, pollutant degradation, disinfection, and organic transformations. The detailed perspective of bismuth-graphene nanohybrids’ applications in various research fields presented herein should be of equal interest to academic and industrial scientists.

Exploring the influence of varying pH on structural, electro-optical, magnetic and photo-Fenton properties of mesoporous ZnFe2O4 nanocrystals

An economically viable and superficial technique was indorsed to yield ZnFe₂O₄ nanocrystals in the system to investigate the impact of pH variation on the optical, structural, electrical, and magnetic properties of as-prepared nanocrystals. The as-synthesized ZnFe₂O₄ nanocrystals were premeditated with the application protracted to degradation of Methylene blue organic dye. The results specify that the pH plays the utmost decisive facet in photo-Fenton recital. From XRD (X-Ray diffraction) analyses, it was confirmed that as-synthesized nanocrystals belong to a cubic Fd3m crystal phase. The crystallite size was also determined by the Scherrer formula and it was noticed that as the pH rises the crystallite size also increased. FT-IR (Fourier Transform Infrared) analysis depicts two absorption peaks ∼ 500 and ∼600 cm^-1 that represents tetrahedral (Td) and octahedral (Oh) sites. Using TEM (Transmission Electron Microscopy), the morphology was observed to be spherical particles with some agglomeration. Photoluminescence and UV-visible spectral studies were performed to investigate the optical properties. The bandgap energy was seen to decrease as the pH increased. Using BET analysis, the surface area for the as-synthesized samples was found to decrease on increasing the pH. The reaction results showed that the ZnFe₂O₄ has good photocatalytic activity, which can be attributed to high surface area and pore volume, and large pore size. The ZnFe₂O₄ produced by the co-precipitation route exhibited promising photocatalytic activity for the removal of textile dye, reaching nearly 99.2% of decolorization at 100 min. Therefore, ZnFe₂O₄ particles rapidly prepared by the co-precipitation route have the potential for use in treatment of textile wastewater by the heterogeneous photo-Fenton process. With the help of VSM analysis, the coercivity and other magnetic properties were determined for the as-synthesized nanocrystal with plays a significant role in photocatalytic recyclability, which intends to premediate that the prepared nanocrystals can be used in industrial persistence.

An eco-friendly and simple sol-gel autocombustion method for synthesis of copper hexaferrite nanostructures: characterization and photocatalytic activity for elimination of water contaminations

In this work, copper hexaferrite (CuFe₁₂O₁₉) nanostructures are successfully synthesized by the sol-gel autocombustion route. Two natural reagents containing pomegranate and beetroot juices are used as green and eco-friendly fuels for synthesis of the nanostructures. The nanostructures are characterized by different techniques such as X-ray diffraction (XRD), energy-dispersive X-ray (EDX), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), and diffuse reflectance spectroscopy (DRS). The results show an appropriate amount of pomegranate juice as a fuel source creating a suitable route for synthesis of CuFe₁₂O₁₉ nanostructures. Therefore, the nanostructures are applied for degradation of different water contaminants containing eosin, erythrosine, rhodamin B, and methyl violet dyes. The comparison of the results shows that the nanostructures are a good photocatalyst for degradation of erythrosine. Therefore, green CuFe₁₂O₁₉ nanostructures can be a good candidate as UV light catalyst for removal of wastewater contaminations.

Investigation of TNT red wastewater treatment technology using the combination of advanced oxidation processes

Different types of advanced oxidation processes and their combinations such as O₃/H₂O₂/UV, O₃/Fenton/UV, O₃/TiO₂/UV, Fenton/H₂O₂/UV, Fenton/TiO₂/UV, TiO₂/H₂O₂/UV, TiO₂/H₂O₂/O₃/UV, TiO₂/O₃/Fenton/UV, TiO₂/H₂O₂/Fenton/UV and O₃/H₂O₂/Fenton/UV were studied for the treatment of undiluted red wastewater from Z113 Factory. The treatment efficiency was evaluated by analyzing chemical oxygen demand (COD) reduction, % degradation of α-TNT, 2,4-DNT, 2,6-DNT, 2,4-DNT-3-SO₃Na and 2,4-DNT-5-SO₃Na. Among studied processes Fenton/TiO₂/O₃/UV was the most effective technology to treat red wastewater. It allows to reduce >99% of COD, α-TNT, 2,4-DNT, 2,6-DNT, 2,4-DNT-3-SO₃Na and 2,4-DNT-5-SO₃Na after 30 h of treatment with optimum operating conditions: rotation speed of 600 rpm, pH of 4 and temperature of 40 °C. According to the chromatograms obtained by gas chromatograph/mass spectrometer (GC/MS), intermediates of the decomposition of pollutants in red wastewater were identified. GC/MS, HPLC, UV-vis and Bacterial Toxicity test were used to assess effluent quality changes before and after treatment. By economic analysis, the studied process had the potential to apply in practice to treat real wastewater at the Z113 Factory.

A synergistic antibacterial platform: combining mechanical and photothermal effects based on Van-MoS2-Au nanocomposites

Herein, we successfully developed a new multifunctional antibacterial system, which combined mechano-bactericidal (Au-nanostars) and photothermal (MoS₂) mechanism. Meanwhile, the targeting molecule of vancomycin was modified on the surface of MoS₂-Au nanocomposites (Van-MoS₂-Au), that generally yield high efficiency in antibacterial performance due to their effective working radii. Van-MoS₂-Au nanocomposites were capable of completely destroying both gram-negative (E. coli) and gram-positive (B. subtilis) bacteria under 808 NIR laser irradiation for 20 min, and nearly no bacterial growth was detected after 12 h incubation. Moreover, these nanocomposites could destruct the refractory biofilm as well, which was a much more difficult medical challenge. The new antibacterial nanomaterials might offer many biomedical applications because of the biocompatibility and strong antibacterial ability.

Heterogeneous Fenton catalysts: A review of recent advances

Heterogeneous Fenton catalysts are emerging as excellent materials for applications related to water purification. In this review, recent trends in the synthesis and application of heterogeneous Fenton catalysts for the abatement of organic pollutants and disinfection of microorganisms are discussed. It is noted that as the complexity of cell wall increases, the resistance level towards various disinfectants increases and it requires either harsh conditions or longer exposure time for the complete disinfection. In case of viruses, enveloped viruses (e.g. SARS-CoV-2) are found to be more susceptible to disinfectants than the non-enveloped viruses. The introduction of plasmonic materials with the Fenton catalysts broadens the visible light absorption efficiency of the hybrid material, and incorporation of semiconductor material improves the rate of regeneration of Fe(II) from Fe(III). A special emphasis is given to the use of Fenton catalysts for antibacterial applications. Composite materials of magnetite and ferrites remain a champion in this area because of their easy separation and reuse, owing to their magnetic properties. Iron minerals supported on clay materials, perovskites, carbon materials, zeolites and metal-organic frameworks (MOFs) dramatically increase the catalytic degradation rate of contaminants by providing high surface area, good mechanical stability, and improved electron transfer. Moreover, insights to the zero-valent iron and its capacity to remove a wide range of organic pollutants, heavy metals and bacterial contamination are also discussed. Real world applications and the role of natural organic matter are summarised. Parameter optimisation (e.g. light source, dosage of catalyst, concentration of H2O2 etc.), sustainable models for the reusability or recyclability of the catalyst and the theoretical understanding and mechanistic aspects of the photo-Fenton process are also explained. Additionally, this review summarises the opportunities and future directions of research in the heterogeneous Fenton catalysis.

Antibacterial and antibiofilm properties of graphene and its derivatives

Infections resulting from bacteria and biofilms have become a huge problem threatening human health. In recent years, the antibacterial and antibiofilm effects of graphene and its derivatives have been extensively studied. However, there continues to be some controversy over whether graphene and its derivatives can resist infection and biofilms. Moreover, the antibacterial mechanism and cytotoxicity of graphene and its derivatives are unclear. In the present review, antibacterial and antibiofilm abilities of graphene and its derivatives in solution, on the surface are reviewed, and their toxicity and possible mechanisms are also reviewed. Furthermore, we propose possible future development directions for graphene and its derivatives in antibacterial and antibiofilm applications.

rGO/Bi2WO6 composite as a highly efficient and stable visible-light photocatalyst for norfloxacin degradation in aqueous environment

Fabrication of binary composite has proved to be an efficient approach to improve the photocatalytic activity of monomer photocatalyst. In this contribution, an effective Reduced Graphene Oxide/Bismuth Tungsten Oxide (rGO/Bi₂WO₆) composite with outstanding photocatalytic activity was designed by employing Bi₂WO₆ as a primary photocatalyst and rGO as an electron acceptor and transporter for norfloxacin degradation in aquatic environment. The rGO/Bi₂WO₆ composite displayed higher photocatalytic activity compare with pure Bi₂WO₆, which could degrade about 87.49% of norfloxacin with 180 min under visible light irradiation. The results of the UV-vis diffuse reflection spectrum, photoluminescence spectra and transient photocurrent response implied that the enhanced photocatalytic activity of the rGO/Bi₂WO₆ composite could be attributed to the improved visible light-harvesting ability and the efficient charge separation ability. Additionally, the reactive-species-trapping experiments indicated that ⋅OH and e^- played dominant roles during the photocatalytic degradation process. Four possible intermediates and two possible transformation pathways of norfloxacin degradation were detected by LC-MS. This present work provided a low-cost and facile green method to design of Bi-based composite.

Development of Polymeric Membranes for Oil/Water Separation

In this work, the treatment of oily wastewater was investigated using developed cellulose acetate (CA) membranes blended with Nylon 66. Membrane characterization and permeation results in terms of oil rejection and flux were compared with a commercial CA membrane. The solution casting method was used to fabricate membranes composed of CA and Nylon 66. Scanning Electron Microscopy (SEM) analysis was done to examine the surface morphology of the membrane as well as the influence of solvent on the overall structure of the developed membranes. Mechanical and thermal properties of developed blended membranes and a commercial membrane were examined by thermogravimetric analysis (TGA) and universal (tensile) testing machine (UTM). Membrane characterizations revealed that the thermal and mechanical properties of the fabricated blended membranes better than those of the commercial membrane. Membrane fluxes and rejection of oil as a function of Nylon 66 compositions and transmembrane pressure were measured. Experimental results revealed that the synthetic membrane (composed of 2% Nylon 66 and Dimethyl Sulfoxide (DMSO) as a solvent) gave a permeate flux of 33 L/m²h and an oil rejection of around 90%, whereas the commercial membrane showed a permeate flux of 22 L/m²h and an oil rejection of 70%.

Modified wheat straw-derived graphene for the removal of Eriochrome Black T: characterization, isotherm, and kinetic studies

A cost-effective and environment-benign adsorbent was prepared from an abundant agro-waste material. Wheat straw was reduced to graphene and then modified by crosslinking to epichlorohydrin. During the conversion process of wheat straw to graphene, the specific surface area increased more than 100 times (from 4 to 415 m² g^-1). The adsorption efficiency of raw wheat straw, graphene nanosheets, and modified graphene against Eriochrome Black T (EBT) were 8.0, 34.7, and 74.4%, respectively. The modified graphene was further investigated for the effect of environmental condition, i.e., pH (3 to 11), EBT concentration (25-100 mg L^-1), adsorbent dosage (0.25-0.75 g L^-1), contact time (5-60 min), and solution temperature (30-60 °C). The dye removal remained at a high level under a wide range of pH from 3 to 9. The EBT removal decreased from 87.3 to 54.5 by increasing dye concentration and increased from 38.2 to 85.4% by increasing adsorbent dose in the studied ranges. Dye removal also increased by mixing time from 5 to 30 min, whereas a slight drop was observed by continuing agitation up to 60 min. Conducting experiments at various temperatures revealed an endothermic process. Pseudo-first-order and pseudo-second-order models were adequate to represent the adsorption kinetics. Isotherm models suggest a multilayer adsorption of EBT molecules on heterogeneous modified graphene surface with a maximum adsorption capacity of 146.2 mg g^-1. The present work demonstrated that the modified graphene obtained from available and low-cost agro-wastes could be used effectively as adsorbent against EBT from aqueous media.

Review on heterogeneous photocatalytic disinfection of waterborne, airborne, and foodborne viruses: Can we win against pathogenic viruses?

Microbial pathogenic contaminations have world widely represented a serious health hazard to humans. Viruses, as a member of microbial contaminants, seriously threaten human health due to their high environmental resistance, having small sizes, and causing an extensive range of diseases. Therefore, selecting an appropriate technology to remove viral contaminants from the air, water, and foods is of prominent significance. Traditional methods for viral disinfection have not proven to be highly practical and effective because they need high energy resources and operational expenses. In recent years, semiconductor-based photocatalysis has attracted more attention in the field of microorganism inactivation due to its outstanding performance and mild reaction conditions. Therefore, this review primarily concentrates on the recent development in viral inactivation/disinfection by heterogeneous photocatalysts. Moreover, the photocatalytic viral inactivation of waterborne, airborne, and foodborne viruses is discussed. Given the appealing merits of heterogeneous photocatalytic disinfection of viruses, there is no doubt that this technology will be an impressively active research field and a source of comfort and confidence to humans in battling against viruses.

Time-dependent study of graphene oxide-trypsin adsorption interface and visualization of nano-protein corona

Understanding of interactions of nanomaterials with biomolecules (especially proteins) is of great importance to the area of nanobiotechnology. Graphene and its derivative such as graphene oxide (GO), are two-dimensional (2-D) nanomaterials with remarkable physical and chemical properties and have been broadly explored in biotechnology and biomedical application. Here, we have reported the nature of adsorption of trypsin on the GO surface, considering its biomedical implications. A simple incubation of trypsin on GO surface exhibits varying resistance to autolysis. The structural morphology of trypsin on the GO surface was studied by using atomic force microscopy (AFM), circular dichroism (CD), fluorescence, and total internal reflection fluorescence (TIRF) microscopies. Results suggest that the trypsin follows the Freundlich Isotherm. By the Langmuir model, the maximum adsorption capacity was found to be 100 mg/g. From protein assay results we have concluded that the native trypsin exhibits the highest catalytic efficiency (33.97*10⁴ L mol^-1 min^-1) in comparison to other Trp-GO constructs. We have further visualized morphological change on GO-trypsin interface throughout the adsorption process by taking samples at definite time intervals, which suggests that the interaction of trypsin with GO is an example of the soft corona. Our findings may be implicated in enzyme engineering as well as enzyme-based bio-sensing applications.

Biomedical Waste Management by Using Nanophotocatalysts: The Need for New Options

Biomedical waste management is getting significant consideration among treatment technologies, since insufficient management can cause danger to medicinal service specialists, patients, and their environmental conditions. The improvement of waste administration protocols, plans, and policies are surveyed, despite setting up training programs on legitimate waste administration for all healthcare service staff. Most biomedical waste substances do not degrade in the environment, and may also not be thoroughly removed through treatment processes. Therefore, the long-lasting persistence of biomedical waste can effectively have adverse impact on wildlife and human beings, as well. Hence, photocatalysis is gaining increasing attention for eradication of pollutants and for improving the safety and clearness of the environment due to its great potential as a green and eco-friendly process. In this regard, nanostructured photocatalysts, in contrast to their regular counterparts, exhibit significant attributes such as non-toxicity, low cost and higher absorption efficiency in a wider range of the solar spectrum, making them the best candidate to employ for photodegradation. Due to these unique properties of nanophotocatalysts for biomedical waste management, we aim to critically evaluate various aspects of these materials in the present review and highlight their importance in healthcare service settings.