Photocatalytic degradation of 2,4-dichlorophenol using bio-green assisted TiO2-CeO2 nanocomposite system

In recent times, cost effective synthesis of semiconductor materials has been a subject of concern for the day to today applications. In this work, novelty has been made on the facile synthesis of metal oxides (TiO₂ and CeO₂) and nanocomposites (TiO₂-CeO₂) through sol-gel and precipitation methods of imparting lemon extract. The synthesized materials behave as the functional catalysts which has been further carried out for the photocatalytic degradation against 2,4-Dichlorophenol (2,4-DCP). The materials are then valued for the structural and optical properties. The lemon extract used in synthesis has played a premier role in upgrading the charge carrier separation, bandgap, and size reduction of the composite system. Further, the CeO₂ supported TiO₂ sample acts as the better visible light catalyst, due to the prevention of aggregation and existence of line dislocation that supported to access the additional electron trap sites.

Charge Carrier Processes and Optical Properties in TiO2 and TiO2-Based Heterojunction Photocatalysts: A Review

Photocatalysis based technologies have a key role in addressing important challenges of the ecological transition, such as environment remediation and conversion of renewable energies. Photocatalysts can in fact be used in hydrogen (H₂) production (e.g., via water splitting or photo-reforming of organic substrates), CO₂ reduction, pollution mitigation and water or air remediation via oxidation (photodegradation) of pollutants. Titanium dioxide (TiO₂) is a “benchmark” photocatalyst, thanks to many favorable characteristics. We here review the basic knowledge on the charge carrier processes that define the optical and photophysical properties of intrinsic TiO₂. We describe the main characteristics and advantages of TiO₂ as photocatalyst, followed by a summary of historical facts about its application. Next, the dynamics of photogenerated electrons and holes is reviewed, including energy levels and trapping states, charge separation and charge recombination. A section on optical absorption and optical properties follows, including a discussion on TiO₂ photoluminescence and on the effect of molecular oxygen (O₂) on radiative recombination. We next summarize the elementary photocatalytic processes in aqueous solution, including the photogeneration of reactive oxygen species (ROS) and the hydrogen evolution reaction. We pinpoint the TiO₂ limitations and possible ways to overcome them by discussing some of the “hottest” research trends toward solar hydrogen production, which are classified in two categories: (1) approaches based on the use of engineered TiO₂ without any cocatalysts. Discussed topics are highly-reduced “black TiO₂”, grey and colored TiO₂, surface-engineered anatase nanocrystals; (2) strategies based on heterojunction photocatalysts, where TiO₂ is electronically coupled with a different material acting as cocatalyst or as sensitizer. Examples discussed include TiO₂ composites or heterostructures with metals (e.g., Pt-TiO₂, Au-TiO₂), with other metal oxides (e.g., Cu₂O, NiO, etc.), direct Z-scheme heterojunctions with g-C₃N₄ (graphitic carbon nitride) and dye-sensitized TiO₂.

Advanced Two-Dimensional Heterojunction Photocatalysts of Stoichiometric and Non-Stoichiometric Bismuth Oxyhalides with Graphitic Carbon Nitride for Sustainable Energy and Environmental Applications

Semiconductor-based photocatalysis has been identified as an encouraging approach for solving the two main challenging problems, viz., remedying our polluted environment and the generation of sustainable chemical energy. Stoichiometric and non-stoichiometric bismuth oxyhalides (BiOX and BixOyXz where X = Cl, Br, and I) are a relatively new class of semiconductors that have attracted considerable interest for photocatalysis applications due to attributes, viz., high stability, suitable band structure, modifiable energy bandgap and two-dimensional layered structure capable of generating an internal electric field. Recently, the construction of heterojunction photocatalysts, especially 2D/2D systems, has convincingly drawn momentous attention practicably owing to the productive influence of having two dissimilar layered semiconductors in face-to-face contact with each other. This review has systematically summarized the recent progress on the 2D/2D heterojunction constructed between BiOX/BixOyXz with graphitic carbon nitride (g-C3N4). The band structure of individual components, various fabrication methods, different strategies developed for improving the photocatalytic performance and their applications in the degradation of various organic contaminants, hydrogen (H2) evolution, carbon dioxide (CO2) reduction, nitrogen (N2) fixation and the organic synthesis of clean chemicals are summarized. The perspectives and plausible opportunities for developing high performance BiOX/BixOyXz-g-C3N4 heterojunction photocatalysts are also discussed.

Selective detection of preferential activity of Lanthanum ion at zinc oxide functionalized nanochannel

A significant increase of rare earth transition metals concentration in water reservoirs caused by the dumping of household materials and petrol-producing industries is a potential threat to human and aquatic life. Here, we demonstrate a model nanofluidic channel for the Lanthanum (La³⁺) ions recognition. To this end, a single conical nanochannel is first modified with poly allylamine hydrochloride followed by immobilization of synthesized ZnO nanoparticles on the channel surface through electrostatic adsorption. A significant change in the nanopore electrical readout is noticed when the functionalized nanochannel is exposed to an electrolyte solution having La³⁺cations. The distinctive response by the nanofluidic system towards La³⁺ions is assumed to be due to ionic radii, hexagonal crystal structure, and associated basal plane interaction between anchored ZnO nanoparticles and La³⁺ions. We anticipate that this nanofluidic system can be used as a model to design highly sensitive metal ion detection devices.

Influence of the Physical Properties on the Antibacterial and Photocatalytic Behavior of Ag-Doped Indium Sulfide Film Deposited by Spray Pyrolysis

Spray pyrolysis was used to deposit indium sulfide (In2S3) films, with or without silver doping. The films are polycrystalline, and the inclusion of Ag in the In2S3 structure leads to the formation of a solid solution, with the crystallite size of the order of tens of nanometers. In2S3 films exhibit a semiconductive behavior, and the incorporation of Ag leads to an increase of the charge carrier concentration, enhancing the electrical conductivity of the films. The small polaron hopping mechanism, deduced by the fittings according to the double Jonscher variation, explains the evolution of the direct current (dc) conductivity at high temperature of the Ag-doped indium sulfide. From impedance spectroscopy, it was found that the doped film presents dielectric relaxation, and Nyquist diagrams indicate the importance of the grain and the grain boundaries’ contributions to the transport phenomena. The physical characteristics of the films have an influence on the photocatalytic performance, achieving photodegradation efficiency above 80% (85.5% in the case of Ag doping), and on the antibacterial activity. The obtained results indicate that indium sulfide films are good candidates for environmental and biological applications, confirming a multifunctional nature.

Microplastics in the environment: Occurrence, perils, and eradication

Microplastics (MPs) with sizes < 5 mm are found in various compositions, shapes, morphologies, and textures that are the major sources of environmental pollution. The fraction of MPs in total weight of plastic accumulation around the world is predicted to be 13.2% by 2060. These micron-sized MPs are hazardous to marine species, birds, animals, soil creatures and humans due to their occurrence in air, water, soil, indoor dust and food items. The present review covers discussions on the damaging effects of MPs on the environment and their removal techniques including biodegradation, adsorption, catalytic, photocatalytic degradation, coagulation, filtration and electro-coagulation. The main techniques used to analyze the structural and surface changes such as cracks, holes and erosion post the degradation processes are FTIR and SEM analysis. In addition, reduction in plastic molecular weight by the microbes implies disintegration of MPs. Adsorptive removal by the magnetic adsorbent promises complete elimination while the biodegradable catalysts could remove 70-100% of MPs. Catalytic degradation via advanced oxidation assisted by S O 4 • - or O H • radicals generated by peroxymonosulfate or sodium sulfate are also adequately covered in addition to photocatalysis. The chemical methods such as sol-gel, agglomeration, and coagulation in conjunction with other physical methods are discussed concerning the drinking water/wastewater/sludge treatments. The efficacy, merits and demerits of the currently used removal approaches are reviewed that will be helpful in developing more sophisticated technologies for the complete mitigation of MPs from the environment.

Recent advances of monoelemental 2D materials for photocatalytic applications

As a sustainable environmental governance strategy and energy conversion method, photocatalysis has considered to have great potential in this field due to its excellent optical properties and has become one of the most attractive technologies today. Among 2D materials, the emerging two-dimensional (2D) monoelemental materials mainly distributed in the -IIIA, -IVA, -VA and -VIA groups and show excellent performance in solar energy conversion due to their graphene-like 2D atomic structure and unique properties, thereby drawing increasing attention. This review briefly summarizes the preparation processes and fundamental properties of 2D single-element nanomaterials, as well as various modification strategies and adjustment mechanisms to enhance their photocatalytic properties. In particular, this article comprehensively discusses the related practical applications of 2D single-element materials in the field of photocatalysis, including photocatalytic degradation for contaminants removal, photocatalytic pathogen inactivation, photocatalytic fouling control and photocatalytic energy conversion. This review will provide some new opportunities for the rational design of other excellent photocatalysts based on 2D monoelemental materials, as well as present tremendous novel ideas for 2D monoelemental materials in other environmental conservation and energy-related applications, such as supercapacitors, electrocatalysis, solar cells, and so on.

Development of eco-friendly CO2-responsive cellulose nanofibril aerogels as "green" adsorbents for anionic dyes removal

A novel CO₂-responsive cellulose nanofibril aerogel as a "green" adsorbent derived from poly(methacrylic acid-co-2-(dimethylamino) ethyl methacrylate) and carboxylated cellulose nanofibrils was successfully prepared via stepwise cation-induced gelation and freeze drying method. This aerogel exhibited CO₂-triggered adsorption behavior towards anionic dyes with a rapid adsorption rate and a high adsorption capacity, as well as satisfactory mechanical properties. Upon CO₂ stimulation, the charged aerogel can selectively adsorb anionic dyes from aqueous solutions based on an electrostatic interaction. The maximum adsorption capacities of this aerogel towards methyl blue (MB), naphthol green B (NGB), and methyl orange (MO) were 598.8, 621.1 and 892.9 mg g^-1, respectively, accompanied by fast adsorption equilibriums towards MB and NGB within 7 min, and MO within 12 min. Meanwhile, the adsorption isotherms and the kinetics of the CO₂-responsive adsorbents followed the Freundlich isotherm and the pseudo-second-order model, respectively. Furthermore, the resulting CO₂-responsive adsorbent exhibited outstanding recyclability, as its adsorption performance can still be maintained even after twenty cycles. Accordingly, the resultant CO₂-responsive cellulose nanofibril aerogel could be a promising adsorbent material for the removal of anionic dyes in wastewater remediation.

Chemico-nanotreatment methods for the removal of persistent organic pollutants and xenobiotics in water - A review

While the technologies available today can generate high-quality water from wastewater, the majority of the wastewater treatment plants are not intended to eliminate emerging xenobiotic pollutants, pharmaceutical and personal care items. Most endocrine disrupting compounds (EDCs) and personal care products (PPCPs) are more arctic than most regulated pollutants, and several of them have acid or critical functional groups. Together with the trace occurrence, EDCs and PPCPs create specific challenges for removal and subsequent improvements of wastewater treatment plants. Various technologies have been investigated extensively because they are highly persistent which leads to bioaccumulation. Researchers are increasingly addressing the human health hazards of xenobiotics and their removal. The emphasis of this review was on the promising methods available, especially nanotechnology, for the treatment of xenobiotic compounds that are accidentally released into the setting. In terms of xenobiotic elimination, nanotechnology provides better treatment than chemical treatments and their degradation mechanisms are addressed.

Continuous adsorptive removal of glimepiride using multi-walled carbon nanotubes in fixed-bed column

Water pollution by emerging pollutants such as pharmaceutical and personal care products is one of today's biggest challenges. The presence of these emerging contaminants in water has raised increasing concern due to their frequent appearance and persistence in the aquatic ecosystem and threat to health and safety. The antidiabetic drug glimepiride, GPD, is among these compounds, and it possesses adverse effects on human health if not carefully administered. Several conventional processes were proposed for the elimination of these persistent contaminants, and adsorption is among them. Therefore, in this study, the adsorptive removal of GPD from water using multi-walled carbon nanotubes (MWCNT) supported on silica was explored on a fixed-bed column. The effects of bed-height, solution pH, and flow rate on the adsorptive removal of GPD were investigated. The obtained adsorption parameters using Sips, Langmuir, and Freundlich models were used to investigate the continuous adsorption. The results showed that the drug removal is improved with the increasing bed height; however, it decreased with the flow rate. The effect of pH indicated that the adsorption is significantly affected and increased in acidic medium. The convection-dispersion model coupled with Freundlich isotherm was developed and used to describe the adsorption breakthrough curves. The maximum adsorption capacity (q_m) was 275.3 mg/g, and the axial dispersion coefficients were ranged between 3.5 and 9.0 × 10⁵ m²/s. The spent adsorbent was successfully regenerated at high pH by flushing with NaOH.

Efficient photocatalytic degradation of dyes using photo-deposited Ag nanoparticles on ZnO structures: simple morphological control of ZnO

In this work, morphology-controlled ZnO structures were prepared via a hydrothermal method by simple adjustments in the NaOH concentration. The NaOH concentration variation from 0.2 to 1.2 M resulted in the formation of ZnO structures in shapes such as walnut, spherical flower, flower, rod, and urchin-like. The extent of OH- ions is the main factor influencing the growth of ZnO structures. Well-defined morphologies, good crystallinity, and optical properties were obtained for all ZnO structures. Among these ZnO structures, ZnOsf (spherical flower-like) structure showed a greater percentage of photodegradation of methyl orange and rhodamine B dyes. Surface plasmon resonance was achieved by modifying the surface of ZnO with Ag nanoparticles. ZnOsf was loaded with Ag nanoparticles by a facile photo-deposition method. Ag-ZnOsf showed superior photoactivity and recyclability for the degradation of methyl orange and rhodamine B. Therefore, modification of different ZnO structures can help realize potential catalysts for future environmental applications.

Fenton/Fenton-like processes with in-situ production of hydrogen peroxide/hydroxyl radical for degradation of emerging contaminants: Advances and prospects

Fenton processes based on the reaction between Fe²⁺ and H₂O₂ to produce hydroxyl radicals, have been widely studied and applied for the degradation of toxic organic contaminants in wastewater due to its high efficiency, mild condition and simple operation. However, H₂O₂ is usually added by bulk feeding, which suffers from the potential risks during the storage and transportation of H₂O₂ as well as its low utilization efficiency. Therefore, Fenton/Fenton-like processes with in-situ production of H₂O₂ have received increasing attention, in which H₂O₂ was in-situ produced through O₂ activation, then decomposed into hydroxyl radicals by Fenton catalysts. In this review, the in situ production of H₂O₂ for Fenton oxidation was introduced, the strategies for activation of O₂ to generate H₂O₂ were summarized, including chemical reduction, electro-catalysis and photo-catalysis, the influencing factors and the mechanisms of the in situ production and utilization of H₂O₂ in various Fenton/Fenton-like processes were analyzed and discussed, and the applications of these processes for the degradation of toxic organic contaminants were summarized. This review will deepen the understanding of the tacit cooperation between the in situ production and utilization of H₂O₂ in Fenton process, and provide the further insight into this promising process for degradation of emerging contaminants in industrial wastewater.

Rational design of bimetallic photocatalysts based on plasmonically-derived hot carriers

Hot carriers generated by plasmonic excitations have recently opened up new avenues in photocatalysis. The transfer of these energetic carriers to adjacent molecules can promote chemical transformations that are important for hydrogen generation by water splitting, CO₂ reduction and degradation of organic pollutants. Here, we have developed and optimised a plasmonic hot-carrier catalytic system based on silica nanoparticles decorated with plasmonic gold nanoparticles as a source of hot carriers, equipped with platinum nanoclusters as co-catalyst for the enhancement of hot-carrier extraction. The latter plays a triple role by providing: a surface favourable for molecular adsorption; hot-electron generation near the nanoclusters due to field enhancement effects and electron momentum relaxation facilitating the electron transfer across the metal surface, exactly where molecules are adsorbed. The combination of plasmonic and catalytic metals in nano-heterostructured devices provides a new platform for photocatalytic processes and is of significant interest for future solar-based clean technologies.

Comparing the Degradation Potential of Copper(II), Iron(II), Iron(III) Oxides, and Their Composite Nanoparticles in a Heterogeneous Photo-Fenton System

Heterogeneous photo-Fenton systems offer efficient solutions for the treatment of wastewaters in the textile industry. This study investigated the fabrication and structural characterization of novel peculiar-shaped Cu^IIO, Fe^III₂O₃, and Fe^IIO nanoparticles (NPs) compared to the properties of the iron(II)-doped copper ferrite Cu^II_0.4Fe^II_0.6Fe^III₂O₄. The photocatalytic efficiencies of these NPs and the composite of the simple oxides (Cu^IIO/Fe^IIO/Fe^III₂O₃) regarding the degradation of methylene blue (MB) and rhodamine B (RhB) as model dyes were also determined. The catalysts were synthesized via simple co-precipitation and calcination technique. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) were utilized for structural characterization. The structure of Cu^IIO was bead-like connected into threads, Fe^III₂O₃ was rod-like, while Fe^IIO pallet-like, with average crystallite sizes of 18.9, 36.9, and 37.1 nm, respectively. The highest degradation efficiency was achieved by Cu^IIO for RhB and by Cu^II_0.4Fe^II_0.6Fe^III₂O₄ for MB. The Cu^IIO/Fe^IIO/Fe^III₂O₃ composite proved to be the second-best catalyst in both cases, with excellent reusability. Hence, these NPs can be successfully applied as heterogeneous photo-Fenton catalysts for the removal of hazardous pollutants. Moreover, the simple metal oxides and the iron(II)-doped copper ferrite displayed a sufficient antibacterial activity against Gram-negative Vibrio fischeri.

Colloidal CdS sensitized nano-ZnO/chitosan hydrogel with fast and efficient photocatalytic removal of congo red under solar light irradiation

Colloidal CdS sensitized nano-ZnO/chitosan (CdS@n-ZnO/CS) hydrogel was prepared and characterized extensively by XRD, SEM-EDS, TEM, UV-Vis DRS, FT-IR and TGA. The photocatalytic activity of CdS@n-ZnO/CS was evaluated with the photodegradation of congo red (CR) as an organic pollutant under solar light irradiation. The influences of initial dye concentration, catalyst dosage, recycling runs, and radical scavenger on decolorization of CR by CdS@n-ZnO/CS were investigated. 95% of CR was removed in just 1 min for 5.0 mg L^-1 and 94.34% of CR was removed in 30 min for 100 mg L^-1. CdS@n-ZnO/CS exhibited an excellent and ultra-fast performance toward CR removal under solar light due to the synergistic effect of adsorption by chitosan and photocatalysis by ZnO and CdS in CdS@n-ZnO/CS hydrogel. Radical trapping control experiments indicated that h⁺ and O₂^- played the major role for CR decolorization. The high performance of CdS@n-ZnO/CS hydrogel was also demonstrated under natural solar light irradiation, suggesting that CdS@n-ZnO/CS hydrogel could be used in practical wastewater treatment.

Understanding and Improving Photocatalytic Activity of Pd-Loaded BiVO4 Microspheres: Application to Visible Light-Induced Suzuki-Miyaura Coupling Reaction

The effective utilization of visible light is required for exploiting photocatalytic reactions in indoor and outdoor environments. In this study, Pd-supported BiVO₄ microspheres (Pd-BiVO₄) were prepared for visible light-induced photocatalytic reactions. Under irradiation with a white light-emitting diode, the obtained Pd-BiVO₄ composite exhibited considerably improved catalytic activity for the decomposition of an organic dye compared with other BiVO₄ catalysts. The Pd-BiVO₄ composite was also effective for catalytic organic transformation via the visible light-induced Suzuki-Miyaura coupling reaction. The photogenerated electrons in the conduction band of BiVO₄ flowed to the Pd nanoparticles and amplified cross-coupling reaction. The influence of the crystal structure and grain size of BiVO₄ and the role of the deposited Pd nanoparticles were fully investigated to elucidate the visible light activity of the catalyst. This system highlights the possibility of an indoor light source with low energy density for sustainable organic transformations.

The removal of metformin and other selected PPCPs from water by poly(3,4-ethylenedioxythiophene) photocatalyst

The objective of this study was to investigate the photocatalytic removal of PPCPs using poly(3,4-ethylenedioxythiophene) (PEDOT) polymer. PEDOT is a conducting polymer that exhibits excellent photocatalytic activity and was used in this study without any additives or metal co-catalysts. The PEDOT was synthesized using chemical oxidative polymerization and characterized further for composition and morphology. PEDOT, in the presence of UV irradiation, showed >99% degradation of one of the most widely prescribed antidiabetic drugs, metformin, within 60 min. The effect of varying concentration of PEDOT, pH, and light irradiance was studied to achieve maximum photocatalytic efficiency. Two major degradation products of metformin of m/z 116 and 126 were detected using triple quadrupole LC-MS/MS, while the degradation kinetics was found to be of pseudo-first-order. Results revealed that photogenerated electrons, holes, and radical species played a role in the PPCPs' degradation. When a mixture of seven PPCPs in the ultra-pure water matrix was tested, more than 99% removal was observed for most of the PPCPs within 60 min. The removal efficiency decreased in a real wastewater effluent due to the presence of dissolved organic matter; however, still, more than 50% removal was observed for majority of the studied PPCPs. The results of PEDOT reusability revealed that the reuse contributed to the drop in the conductivity and subsequent drop in the photocatalytic activity; however, a simple acid treatment was found to be effective to recoup its conductivity. PEDOT was successfully immobilized on an electrospun fiber mat to enhance its applicability.

Pesticides in Drinking Water-A Review

The ubiquitous problem of pesticide in aquatic environment are receiving worldwide concern as pesticide tends to accumulate in the body of the aquatic organism and sediment soil, posing health risks to the human. Many pesticide formulations had introduced due to the rapid growth in the global pesticide market result from the wide use of pesticides in agricultural and non-agricultural sectors. The occurrence of pesticides in the water body is derived by the runoff from the agricultural field and industrial wastewater. Soluble pesticides were carried away by water molecules especially during the precipitation event by percolating downward into the soil layers and eventually reach surface waters and groundwater. Consequently, it degrades water quality and reduces the supply of clean water for potable water. Long-time exposure to the low concentration of pesticides had resulted in non-carcinogenic health risks. The conventional method of pesticide treatment processes encompasses coagulation-flocculation, adsorption, filtration and sedimentation, which rely on the phase transfer of pollutants. Those methods are often incurred with a relatively high operational cost and may cause secondary pollution such as sludge formation. Advanced oxidation processes (AOPs) are recognized as clean technologies for the treatment of water containing recalcitrant and bio-refractory pollutants such as pesticides. It has been adopted as recent water purification technology because of the thermodynamic viability and broad spectrum of applicability. This work provides a comprehensive review for occurrence of pesticide in the drinking water and its possible treatment.

Facile synthesis, characterization, mechanism and enhanced visible-light photocatalytic activity of SiW12/α-Fe2O3 nanocomposites

The photocatalytic mechanism of the SiW12/α-Fe2O3 nanohybrid.

Antibacterial Performance of a Gold-Loaded g-C3 N4 Nanocomposite System in Visible Light-Dark Dual Mode

Semiconductor photocatalysis technology, which can kill pathogenic microorganisms in a green and broad-spectrum way, is a new research field with great application potential. Due to the dependence on light, semiconductor materials have the problems of low utilization rate of sunlight and inactivation under dark conditions. A simple Au-loaded g-C₃ N₄ (Au/g-C₃ N₄ ) nanocomposites was studied. Under dark conditions, the antibacterial efficiency of 1.2 % Au/g-C₃ N₄ reached 99.1 % relative to 10⁵  CFU (Colony-FormingUnits)/mL E. coli. Under light conditions, the antibacterial efficiency of 0.9 % Au/g-C₃ N₄ reached 94.1 % relative to 10⁷  CFU/mL E. coli. The influence of contact time, Au loading and bacterial concentration on its antibacterial performance under dark conditions was discussed in detail. Through photoelectrochemistry, SEM, TEM and reactive oxygen species (ROS) detection the microscopic charge behaviour was revealed in the system, and a light-dark dual-mode antibacterial mechanism was proposed.

Facile synthesis of chitosan membranes for visible-light-driven photocatalytic degradation of tetracycline hydrochloride

Due to the film-forming ability of polymers, a variety of photocatalytic membranes (PMs) based on polymers easily being separated and reused have been constructed for wastewater contaminant treatment. During their construction processes, chitosan (CS) as a bio-polymer with its distinct merits of abundant resources, low-cost and environmental-friendliness, as well as formability and ease of modification, has attracted great attention. However, the role of CS was mostly believed to be just a support or an adsorbent for fixing or dispersing photocatalysts. Whether CS possessed photocatalytic activity or not still remained vague. Herein, in this work, CS membranes (CSM) were facilely prepared for photocatalytic degradation of tetracycline hydrochloride (TC, a model organic pollutant) in aqueous solution, and its photocatalytic performance was investigated and compared with that of CSP (CS powder) and TiO2-P25 (a commercially used photocatalyst). The results showed that the single-phased CSM exhibited a better visible light photocatalytic activity. After visible light irradiation for 60 minutes, the degradation efficiency of TC can reach above 90% when the CSM was used as a photocatalyst, while with the same irradiation time interval, less TC could be degraded over both CSP and TiO2-P25. Through radical scavenging and EPR experiments, ˙O2 - and h+ were found to be the main active oxygen species generated in the reaction system for TC degradation. After being washed with 2 wt% NaOH solution, the CSM revealed a good recyclability implying its potential for practical applications. This study would provide a certain theoretical and data basis for the future development of CS-based PMs and photocatalysts.

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.

2D Nanocomposite Membranes: Water Purification and Fouling Mitigation

In this study, the characteristics of different types of nanosheet membranes were reviewed in order to determine which possessed the optimum propensity for antifouling during water purification. Despite the tremendous amount of attention that nanosheets have received in recent years, their use to render membranes that are resistant to fouling has seldom been investigated. This work is the first to summarize the abilities of nanosheet membranes to alleviate the effect of organic and inorganic foulants during water treatment. In contrast to other publications, single nanosheets, or in combination with other nanomaterials, were considered to be nanostructures. Herein, a broad range of materials beyond graphene-based nanomaterials is discussed. The types of nanohybrid membranes considered in the present work include conventional mixed matrix membranes, stacked membranes, and thin-film nanocomposite membranes. These membranes combine the benefits of both inorganic and organic materials, and their respective drawbacks are addressed herein. The antifouling strategies of nanohybrid membranes were divided into passive and active categories. Nanosheets were employed in order to induce fouling resistance via increased hydrophilicity and photocatalysis. The antifouling properties that are displayed by two-dimensional (2D) nanocomposite membranes also are examined.

Aggregation-induced photocatalytic activity and efficient photocatalytic hydrogen evolution of amphiphilic rhodamines in water

The development of photocatalysts is an essential task for clean energy generation and establishing a sustainable society. This paper describes the aggregation-induced photocatalytic activity (AI-PCA) of amphiphilic rhodamines and photocatalytic functions of the supramolecular assemblies. The supramolecular assemblies consisting of amphiphilic rhodamines with octadecyl alkyl chains exhibited significant photocatalytic activity under visible light irradiation in water, while the corresponding monomeric rhodamines did not exhibit photocatalytic activity. The studies on the photocatalytic mechanism by spectroscopic and microscopic analyses clearly demonstrated the AI-PCA of the rhodamines. Moreover, the supramolecular assemblies of the rhodamines exhibited excellent photocatalytic hydrogen evolution rates (up to 5.9 mmol g-1 h-1).

Cotton fabrics decorated with nanostructured Ag/AgX (X:Cl,Br) as reusable solar light-mediated bactericides: A comparative study

In this study, cotton fabrics decorated with Ag/AgCl and Ag/AgBr NPs were produced by a simple hydrothermal treatment using AgCl and AgBr as precursors. Their morphological features as well as, chemical composition and structural and luminescence properties were compared. Their water disinfection aptitude against E. coli and S. aureus was also investigated under solar illumination in batch as well asin dynamic conditions. The highest activity was observed for Cot-Ag/AgCl with a quasi-complete inactivation of E. coli and S. aureus(1.5 × 10⁷cfu mL^-1) within 15 min illumination. Disinfection efficiency under continuous flow was also tested using a home-made photoreactor and the cotton fabrics with the most efficient photocatalyst (Ag/AgCl). It has shown to be efficient at least for 10 cycles revealing the robustness of the functionalization. The mechanism of photocatalytic disinfection was explained in terms of the surface plasmon resonance (SPR) induced by the presence of Ag NPs, the resulting holes, h⁺, being one of the most intervenient species in the disinfection mechanism. The difference in the photocatalytic efficiency between AgCl and AgBr functionalized cotton was attributed to differences in the carriers (h⁺and e-) lifetime. This work provides a proof of concept for the potential applicability of Cot-Ag/AgCl or Cot-Ag/AgBr for in-flow potabilization of water under solar illumination.

Historical development and prospects of photocatalysts for pollutant removal in water

Photocatalysis, as a low-cost and environment friendly technology, has demonstrated a significant potential for water pollution purification; it has received extensive attention in recent decades. The key is the photocatalyst; a large number of photocatalysts have been developed. To better understand and further develop the photocatalysis technology for water treatment, this review summarizes its development over time. The development period is divided into four stages (1960s-1993, 1994-2000, 2001-2010, and 2011-present) to provide readers with a better understanding of the development characteristics, and causes and consequences of each historical stage. This review expounds the origin and development of photocatalysis and the obstacles encountered and overcome. It describes the development of mechanisms and methods to solve these problems in each time period. Moreover, it reviews the recent development of new photocatalysts, the concept of designing photocatalysts, and photocatalytic-coupling systems. Finally, it enumerates the problems that continue to exist in the application of photocatalysis technology, and highlights the key issues that must be addressed in future research. The review is aimed at providing the researchers with a deeper understanding of photocatalysis technology and encourage further development of the application of photocatalysis to water treatment.

Impact of Titanium Dioxide (TiO2) Modification on Its Application to Pollution Treatment—A Review

A high-efficiency method to deal with pollutants must be found because environmental problems are becoming more serious. Photocatalytic oxidation technology as the environmentally-friendly treatment method can completely oxidate organic pollutants into pollution-free small-molecule inorganic substances without causing secondary pollution. As a widely used photocatalyst, titanium dioxide (TiO2) can greatly improve the degradation efficiency of pollutants, but several problems are noted in its practical application. TiO2 modified by different materials has received extensive attention in the field of photocatalysis because of its excellent physical and chemical properties compared with pure TiO2. In this review, we discuss the use of different materials for TiO2 modification, highlighting recent developments in the synthesis and application of TiO2 composites using different materials. Materials discussed in the article can be divided into nonmetallic and metallic. Mechanisms of how to improve catalytic performance of TiO2 after modification are discussed, and the future development of modified TiO2 is prospected.

A radially controlled ZnS interlayer on ultra-long ZnO-Gd2S3 core-shell nanorod arrays for promoting the visible photocatalytic degradation of antibiotics

Nanorod (NR) arrays offer commendable visible-light-driven photocatalytic performances. Herein, we describe the construction of a ternary ZnO-ZnS-Gd₂S₃ nanostructural array in which a sulfidation process is used to decorate a Gd₂S₃ shell layer with a ZnS interface over vapor-phase-grown vertically-aligned ZnO. With control over the shell-wall thickness, the shell layer of ∼25 nm wall thickness on the ultra-long ZnO NR arrays exhibited a higher catalytic efficiency close to 3.3, 2.0, 1.2, and 1.8 times those of the bare ZnO, the ZnO-ZnS, the Gd₂S₃-decorated (∼10 nm) and Gd₂S₃ shell-layered (∼40 nm) ZnO-ZnS core-shell structures, respectively. The core-shell geometry and the shell-wall thickness with maximized contact interface afforded increased light absorption in the visible region and effectively retarded the recombination rate of the photoinduced charge carriers by confining electrons and holes separately, thus providing advantages in terms of the degradation of the pharmaceutical residue tetracycline and the industrial pollutant 4-nitrophenol in wastewater.