Fabrication of dual Z-scheme photocatalyst via coupling of BiOBr/Ag/AgCl heterojunction with P and S co-doped g-C3N4 for efficient phenol degradation

Facile synthesis of double-cross-linked alginate-based hydrogel: Characterization and use in a context of circular economy for cationic dye removal

Hydrogels based on natural polysaccharides have received special attention in the last decade due to their interesting features, such as availability, biocompatibility, biodegradability and safety. Such characteristics may make them sustainable and eco-friendly materials for water and wastewater treatment, meeting the concept of circular economy. In this study, a novel double-cross-linked alginate-based hydrogel has been successfully synthesized using epichlorhydrin and sodium trimetaphosphate (STMP) as cross-linker agents and then used for the removal of methylene blue (MB) dye under different operating conditions. The obtained hydrogel was deeply characterized by using various analytical techniques, namely Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Experimental results showed that the synthesized double cross-linked hydrogel with relatively high STMP concentration (0.26 M) has promising structural and textural properties. This material exhibited excellent removal ability towards MB with a maximum adsorption capacity of about 992 mg/g for an initial pH of 10. The kinetic and isotherm modeling study revealed that the pseudo-second-order and Freundlich models fitted well the measured adsorption experimental data. The MB adsorption process onto the synthesized hydrogel is exothermic, feasible and spontaneous. It mainly includes electrostatic interaction and hydrogen bonds. These findings suggest that double-cross-linked alginate-based hydrogel can be considered as an attractive and potential adsorbent for an effective cationic dye removal from aqueous environments. The use of such a green adsorbent for the treatment of organic-pollutants-rich industrial wastewaters promotes sustainability and circular economy concepts.

A novel competitive fluorescence colorimetric dual-mode immunosensor for detecting ochratoxin A based on the synergistically enhanced peroxidase-like activity of AuAg NCs-SPCN nanocomposite

The sensitive and rapid detection of Ochratoxin A in foods is particularly urgent for ensuring human security due to its larger toxicity to the body. Herein, a novel competitive fluorescence colorimetric dual-mode immunosensor for detecting Ochratoxin A based on AuAg NCs-SPCN nanocomposite was designed and constructed. The synergistic effect of SPCN and AuAg NCs dramatically improved the nanozyme activity. The fluorescence intensity was enhanced due to the aggregation luminescence effect, and a new emission peak appeared at 440 nm to form a fluorescence signal. For colorimetric, H2O2 was effectively decomposed by AuAg NCs-SPCN to form ·OH groups and oxidize 3,3',5,5'-tetramethylbenzidine to blue oxTMB. The dual-mode immunosensor showed a good linear relationship from 0.001 μg/L to 10 μg/L and the detection limits were 0.155 ng/L (fluorescence) and 0.213 ng/L (colorimetric). So, this dual-mode immunosensor would have a potential applicative prospect for sensitive detecting Ochratoxin A and other small molecules.

Degradation of phenol in wastewater through an integrated dielectric barrier discharge and Fenton/photo-Fenton process

In this study, a non-thermal dielectric barrier discharge-Fenton/photo-Fenton process was investigated to remove phenol from synthetic wastewater. The changes and optimal values of influencing parameters, including treatment time, iron concentration, phenol initial concentration, and pH, were investigated based on the central composite design (CCD) method. The presence of 0.4 mmol/L of iron in the phenol solution with a concentration of 100 mg/L increased the removal efficiency and pseudo-first-order kinetic constant compared to dielectric barrier discharge cold plasma (DBDP) alone from 0.0824 min-1 and 56.8% to 0.2078 min-1 and 86.83%, respectively. The phenol removal efficiency was reduced to 52.9%, 45.6% and 31.8% by adding tert-butyl alcohol (TBA) with concentrations of 50, 100, and 200 mg/l, respectively. After 12 min of DBDP irradiation, the pH of the sample decreased from 5.95 to 3.42, and the temperature of the sample increased from 19.3 to 37.2 degrees Celsius. The chemical oxygen demand (COD) of the sample containing 100 mg/L phenol under plasma-Fenton/photo-Fenton irradiation decreased from 241 mg/L to 161 mg/L. Phenol removal efficiency after 10 min of treatment in the presence of 0.4 mmol/L of iron with the reactor volume of 50 mL was 87%, but the efficiency decreased to 76%, 47%, and 9% by increasing the volume to 100, 200, and 400 mL, respectively. Reducing the power led to a decrease in the removal efficiency from 56.8% for 100 W power to 10.8% for 40 W. The energy efficiency for 50% removal by DBDP and plasma-Fenton/photo-Fenton systems was 5.86×10-3 kWh/mg and 1.27×10-3 kWh/mg, respectively.

3D kaolinite/g-C3N4-alginate beads as an affordable and sustainable photocatalyst for wastewater remediation

Graphitic carbon nitride (GCN) is an efficient visible-light-driven metal-free semiconductor with superior photocatalytic activity. However, the main drawbacks of GCN include lower adsorption capacity, poor reusability and recoverability. To address these drawbacks, kaolinite/g-C3N4-alginate beads were fabricated using a cross-linking method to remove brilliant green dye from wastewater via photocatalysis. The characterization studies proved the alginate's potential capability in altering photocatalyst bandgap (2.78 to 2.55 eV) and minimizing recombination of electron-hole pairs. Kaolinite/g-C3N4-alginate photocatalyst removed 97 % of brilliant green (10 mg/L) in 90 min under visible light irradiation. The superior performance of the kaolinite/g-C3N4-alginate beads was ascribed to its improved adsorption and effective utilization of visible light. The key advantages of kaolinite/g-C3N4-alginate beads were their quick recovery and extended reusability upto ten cycles. The sustainability metrics analysis of kaolinite/g-C3N4-alginate beads confirmed the environmental suitability and practicability in wastewater remediation. This study provides new insights into the low-cost and sustainable preparation of highly reusable g-C3N4-based photocatalysts for environmental remediation.

Influence of wastewater matrix on the visible light degradation of phenol using AgCl/Bi24O31Cl10 photocatalyst

A significant amount of research has been conducted on the development and application of photocatalytic materials for the visible light degradation of organic pollutants in wastewater. However, most pollutant degradation studies are conducted using simulated wastewater often prepared using DI water. This is far removed from the realities of environmentally relevant water systems. It is therefore important to investigate the activity of these semiconductor materials with real water samples. In this study, the photocatalytic activity of the photocatalyst was investigated in the secondary effluent of a wastewater treatment plant (WWTP) in Pretoria, South Africa, for the degradation of phenol under visible light irradiation. The experimental design was done using the Taguchi method L16 orthogonal tray with three factors (pH, initial phenol concentration, and photocatalyst dosage) and four levels. The results show that pH is the highest-ranked significant factor influencing the degradation rate, closely followed by the initial concentration of the pollutant. The photocatalyst dosage had the least significant impact on degradation. The effects of individual anion components such as Cl-, NO3-, NO2-, SO42- and cations such as Ca2+, Mg2+, Zn2+, and K+ were investigated. While Cl- did not negatively influence the degradation rate, the results show that NO3- and SO42- inhibit the degradation of phenol. More specifically, the presence of nitrites resulted in total impeding of the degradation process illustrating that nitrite concentrations ≥ 20 ppm should be removed from wastewater prior to photocatalytic degradation. The cations investigated promoted the degradation of phenol. Generally, there was enhanced degradation in the water matrix when compared to DI water, and the results revealed improved degradation efficiency due to the cumulative impact of various components of the wastewater.

An Overview of Recent Developments in Improving the Photocatalytic Activity of TiO2-Based Materials for the Treatment of Indoor Air and Bacterial Inactivation

Indoor air quality has become a significant public health concern. The low cost and high efficiency of photocatalytic technology make it a natural choice for achieving deep air purification. Photocatalysis procedures have been widely investigated for environmental remediation, particularly for air treatment. Several semiconductors, such as TiO₂, have been used for photocatalytic purposes as catalysts, and they have earned a lot of interest in the last few years owing to their outstanding features. In this context, this review has collected and discussed recent studies on advances in improving the photocatalytic activity of TiO₂-based materials for indoor air treatment and bacterial inactivation. In addition, it has elucidated the properties of some widely used TiO₂-based catalysts and their advantages in the photocatalytic process as well as improved photocatalytic activity using doping and heterojunction techniques. Current publications about various combined catalysts have been summarized and reviewed to emphasize the significance of combining catalysts to increase air treatment efficiency. Besides, this paper summarized works that used these catalysts to remove volatile organic compounds (VOCs) and microorganisms. Moreover, the reaction mechanism has been described and summarized based on literature to comprehend further pollutant elimination and microorganism inactivation using photocatalysis. This review concludes with a general opinion and an outlook on potential future research topics, including viral disinfection and other hazardous gases.

Understanding the Principles and Applications of Dual Z-Scheme Heterojunctions: How Far Can We Go?

In the past seven years, dual Z-scheme heterojunctions evolved as favorable approaches for enhanced charge carrier separation through direct or indirect charge transfer transportation mechanisms. The dynamics of the charge transfer is the major strategy for understanding their photoactivity and stability through the formation of distinctive redox centers. The understanding of currently recognized principles for successful fabrication and classification in different energy and pollution remediation strategies is discussed, and a universal charge transfer-type-based classification of dual Z-schemes that can be adopted for Z-scheme and S-scheme heterojunctions is proposed. Methods used for determining the charge transfer as proof of dual Z-scheme existence are outlined. Most importantly, a new macroscopic N-scheme and a triple Z-scheme that can also be adopted as triple S-scheme heterostructures composed of four semiconductors are proposed for generating both oxidatively and reductively empowered systems. The proposed systems are expected to possess properties that enable them to harvest solar light to drive important chemical reactions for different applications.

Construction of a ternary staggered heterojunction of ZnO/g-C3N4/AgCl with reduced charge recombination for enhanced photocatalysis

In this study, a series of ternary composite photocatalysts ZnO/g-C₃N₄/AgCl(x) (x is the amount of AgCl added, x=0.05, 0.1, 0.15 g) were synthesized, and various characterization methods were used to analyze the morphology, structural, and photochemical properties of the above samples. The photocatalytic activity of the obtained samples was evaluated by degrading rhodamine B (RhB) and acid orange (AOII) under xenon lamp irradiation. The results show that the degradation rate of ZnO/g-C₃N₄/AgCl (0.1 g) is 99% within 60 min, which is much higher than the 38% degradation rate of g-C₃N₄. After five cycles, the degradation efficiency of RhB and AOII by ZnO/g-C₃N₄/AgCl (0.1 g) were still 85% and 94%, respectively. In addition to colored dyes, the photocatalytic degradation of colorless tetracycline hydrochloride (TCH) compounds was also investigated to understand the effect of photosensitization on the degradation process. Based on the electronic structure analysis of the DFT calculations, a staggered heterojunction structure was found between g-C₃N₄, ZnO, and AgCl. The enhanced photocatalytic activity of the ternary composite is mainly attributed to the efficient separation of charge carriers through the synergistic removal of photogenerated electrons in g-C₃N₄ by ZnO and AgCl. Radical trapping experiments confirmed that •O₂^- and h⁺ were the main active species in the reaction system. As a visible light-responsive catalyst, ZnO/g-C₃N₄/AgCl can be effectively applied to the degradation of organic dye pollutants and has broad application prospects.

Ultrahigh-efficient BiOBr-x%La@y%CNQDs nanocomposites with enhanced generation and separation of photogenerated carriers towards bisphenol A degradation and toxicity reduction

In this study, a series of hierarchical flower-like La-doped BiOBr composites modified with carbon nitride quantum dots (BiOBr-x%La@y%CNQDs) was synthesized using a microwave solvothermal method in combination with a calcination method. It was found that La doping and CNQDs co-decorated with BiOBr showed much better photoreactivity for bisphenol A (BPA) degradation than pure BiOBr. The best degradation and mineralization efficiencies of BPA were 100% and 77% within 12 min at La and CNQDs contents of 1% and 1.25%, respectively. Various characterization results demonstrated that this synergistic effect on BiOBr-1%La@1.25%CNQDs was attributed to its improved light-harvesting properties, enhanced photogenerated electron and holes pairs separation and interfacial charge transfer. Degradation pathways were proposed based on active species analysis, identification of nine intermediates, and density functional theory (DFT) calculations. Furthermore, a bioluminescence assay of the inhibition rate of the luminescent bacterium Vibrio qinghaiensis sp. Q67 showed that BiOBr-1%La@1.25%CNQDs have superior detoxification ability. The present study provides some insight into the design of ultrahigh-efficiency nanojunction photocatalysts with a broadened photoabsorption range and improved separation efficiency of photogenerated carriers to enhance the degradation and detoxification performance of BPA.

New generation advanced nanomaterials for photocatalytic abatement of phenolic compounds

Nowadays, organic pollutants create severe problems worldwide. Phenolic compounds are the harmful pollutants that are developed from industrial effluents, thus causing several environmental problems. Low-cost materials show good potential capabilities for removal of phenolic compounds but are not so effective, so modification is required. New generation nanocatalysts are thought to be excellent for phenol removal. Removal of phenolic pollutants by photodegradation may lead to the decrement of these problematic groups. In this review, (i) a new generation of catalysts for the removal of phenolic compounds is discussed, (ii) nanocatalysts for photodegradation processes, and (iii) the mechanisms involved in photodegradation processes are also discussed. It is noticeable from the analysis that new generation catalysts for photodegradation processes have been demonstrated for high removal abilities of irrefutable phenolic compounds. Finally, future perspectives are also given in this article for the further development of next-generation catalysts.

Recent advances of carbon-based nanomaterials (CBNMs) for wastewater treatment: Synthesis and application

Carbon-based nanomaterials (CBNMs) have attracted significant alert due to the affluent science underpinning their implementations associated with a novel mixture of high aspect proportions, greater thermal and electrical performance, outstanding optical features, and high exterior area. CBNMs not only bear assurance in a broad range of implementations in medication, nano and microelectronics, and ecological remedies but may also be utilized in practical laboratory determinations. More specifically, CBNMs perform as an outstanding adsorbent in terminating heavy metal ions (HMI) from wastewater. There is presently a deficiency of powerful threat inspection instruments owing to their complex detection and related deficit in the health risk database. Therefore, our present review concentrates on spreading CBNMs to release pollutants from wastewater. The article wraps the effect of these contaminants and photocatalytic strategies towards treating these mixtures in wastewater, along with their restrictions and challenges, convincing resolutions, and possibilities of these approaches.

Use of biomass-derived biochar in wastewater treatment and power production: A promising solution for a sustainable environment

Over the past few years, we are witnessing the advent of a revolutionary bioengineering technology in biochar production and its application in waste treatment and an important component in power generation devices. Biochar is a solid product, highly rich in carbon, whose adsorption properties are ideal for wastewater decontamination. Due to its high specific surface area to volume ratio, it can be utilized for many environmental applications. It has diverse applications in various fields. This review focuses on its various applications in wastewater treatment to remove various pollutants such as heavy metals, dyes, organic compounds, and pesticides. This review also highlights several energy-based applications in batteries, supercapacitors, and microbial fuel cells. It described information about the different feedstock materials to produce LB-derived biochar, the various conditions for the production process, i.e., pyrolysis and the modification methods of biochar for improving properties required for wastewater treatment. The present review helps the readers understand the importance of biochar in wastewater treatment and its application in power generation in terms of batteries, supercapacitors, microbial fuel cells, applications in fuel production, pollutant and dye removal, particularly the latest development on using LB-derived biochar. This review also highlights the economic and environmental sustainability along with the commercialization of biochar plants. It also describes various pyrolytic reactors utilized for biochar production.

Co-Doped, Tri-Doped, and Rare-Earth-Doped g-C3N4 for Photocatalytic Applications: State-of-the-Art

Rapid industrialization and overpopulation have led to energy shortages and environmental pollution, accelerating research to solve the issues. Currently, metal-free photocatalysts have gained the intensive attention of scientists due to their environmental-friendly nature and ease of preparation. It was noticed that g-C3N4 (GCN) consists of a few outstanding properties that could be used for various applications such as water treatment and clean energy production. Nonetheless, bare GCN contains several drawbacks such as high charge recombination, limited surface area, and low light sensitivity. Several solutions have been applied to overcome GCN limitations. Co-doping, tri-doping, and rare-earth-doping can be effective solutions to modify the GCN structure and improve its performance toward photocatalysis. This review highlights the function of multi-elemental and rare-earth dopants in GCN structure, mechanisms, and performance for photocatalytic applications as well as the advantages of co-doping, tri-doping, and rare-earth-doping of GCN. This review summarizes the different roles of dopants in addressing the limitations of GCN. Therefore, this article critically reviewed how multi-elemental and rare-earth-doping affect GCN properties and enhanced photoactivity for various applications.

Novel synthesis methods and applications of MXene-based nanomaterials (MBNs) for hazardous pollutants degradation: Future perspectives

MXenes are a quickly growing and extended group of two-dimensional (2D) substances that have earned unbelievable analysis credits for various application areas within different manufacturing areas. Due to novel essential architectural and physicochemical properties shows good properties, such as elevated exterior area, living adaptability, strong electrochemistry, and great hydrophilicity. Given the fast progress within the structure and synthesis of MBNs for water treatment, quick updates on this research field are required to remove toxic substances, such as production approaches and characterization methods for the advantages and constraints of MXenes for pollutant degradation. MXenes are determined as a proposed road toward atmosphere-clean-up machinery to identify and decrease a pattern of hazardous resistant pollutants from environmental forms. Here, in this review article, we have been focused on describing the overview, novel synthesis methods, and characteristics of the MXene-based nanomaterials (MBNs) in the field for removing hazardous contaminants from environmental conditions. In the last, the utilizations of MBNs in water sanitization, organic solvent filtration, antibiotics degradation, pesticide degradation, heavy metals degradation, ions removal, bacterial pathogens degradation, along with the conclusion, challenges, and prospects in this field, have been discussed.

Synthesis and characterisation of zinc oxide modified biorenewable polysaccharides based sustainable hydrogel nanocomposite for Hg2+ ion removal: Towards a circular bioeconomy

Industrial metal ion pollution has been considered the chief source of water contaminants all over the world. In the present research, we have prepared gum tragacanth cross-linked 2-hydroxyethyl methacrylate-co-acrylamide (GT-cl-(HEMA-co-AAm)) hydrogel and gum tragacanth cross-linked 2-hydroxyethyl methacrylate-co-acrylamide/zinc oxide (GT-cl-(HEMA-co-AAm)/ZnO) hydrogel composite with better Hg²⁺ adsorption capability. GT-cl-(HEMA-co-AAm)/ZnO hydrogel composite (154.8 mg g^-1) exhibited higher Hg²⁺ adsorption than GT-cl-(HEMA-co-AAm) hydrogel. To address the performance of GT-cl-(HEMA-co-AAm) hydrogel and GT-cl-(HEMA-co-AAm)/ZnO hydrogel composite, batch adsorption experiments were successfully conducted under different optimised conditions. At last, in-vitro antibacterial activities of Hg²⁺ loaded GT-cl-(HEMA-co-AAm) and GT-cl-(HEMA-co-AAm)/ZnO were performed in two different well Staphylococcus aureus (gram-positive) and Pseudomonas aeruginosa (gram-negative) bacteria. As a positive control, ampicillin was employed against both types of bacteria. This methodology for the reusability of material has a great ecofriendly impression for minimising secondary waste derived from adsorption and can help design upgraded antibacterial agents.

Perovskite oxides for oxygen transport: Chemistry and material horizons

Oxygen permeable membrane, which has the advantages of high separation selectivity, low energy consumption and simple process in oxygen separation, can be used in the fields of environment and energy, such as pure oxygen preparation, fuel cell, oxygen-enriched combustion and chemical reactor for methane catalytic conversion (e.g. partial oxidation of methane, carbon dioxide reforming with methane). New materials and technological development are needed to achieve this target for GHG reformation. In this direction, mixed ionic-electronic conducting (MIEC) oxides based on perovskite oxides are one of the prominent materials for oxygen transport at high temperatures. These compounds were created into solid ceramic membranes with considerable electronic and oxygen ionic conductivity. As a result of the differential partial pressure of oxygen across the membrane, this process enables the ionic transfer of oxygen from the air, providing the driving force for oxygen ion transport. Notably, over the last 40 years, the defect theory has been applied to a wide range of MIEC materials, providing insight into electronic and ionic transport, widely applied to designing catalysts for wastewater treatment and gas purification. However, a critical review by in-depth analysis from the material side on perovskite oxides for oxygen transport is needed. This work evaluates the research community's significant and relevant contributions in the perovskite oxides for gas separation domain over the previous four decades in conjunction with theoretical concepts, which would give rise to the fundamental understanding of the impact of various transitional metal elements on oxygen transport performance and stability in a different atmosphere.

Hydroxyl regulating effect on surface structure of BiOBr photocatalyst toward high-efficiency degradation performance

Herein, photocatalytic degradation of levofloxacin hydrochloride (LVF) by a simple surface hydroxyl strategy on BiOBr photocatalyst was studied under simulated visible light irradiation. Interestingly, the BiOBr contained abundant hydroxyl groups following its modification with glucose, which enhanced the photocatalytic degradation of levofloxacin hydrochloride (LVF). The degradation efficiency of LVF over the optimized composite of BiOBr-5 could reach 91.67% in 20 min, which was much higher than that of pristine BiOBr (59.26%). Following, the biotoxicity of antibiotics to Escherichia coli DH5a could be eliminated after LVF photocatalytic degradation. This strategy proposed in this work can provide new ideas for tuning the surface structures of photocatalysts via specific functional groups for the highly efficient degradation and efficient removal of antibiotics in wastewater.

Synthesis of Bio-based monomers and polymers using microbes for a sustainable bioeconomy

As a result of environmental concerns and the depletion of biomass assets, eco-friendly, renewable biomass-based chemical extraction has recently received significant attention. Bio-based chemicals can be prepared using different renewable feedstockbio-resources through microbial fermentation. Chemicals produced from renewable feedstockscan reduce ecological consequences from improper disposal and repurpose them into valuable products. Biodegradability, biocompatibility and non-toxicity, particularly in biomedical applications, have inspired researchers towards developing novel technologies that have social benefit. Among semi-synthetic and synthetic polymeric materials, utilization of natural bio-based monomeric materials can provide opportunities for sustainable development of novel non-toxic, biodegradable and biocompatible products. The purpose of this work is to give a summary of research into the generation of natural bio-based succinic acid (SA) monomer, the development of poly(butylene succinate) (PBS) as biodegradable polymer, PBS-based nanocomposites and their innovative uses.

Fabrication of a dual S-scheme Bi7O9I3/g-C3N4/Bi3O4Cl heterojunction with enhanced visible-light-driven performance for phenol degradation

S-scheme heterostructure can facilitate the separation of carriers while maintain outstanding redox capacity. A series of ternary Bi₇O₉I₃/g-C₃N₄/Bi₃O₄Cl photocatalytic system was triumphantly synthesized via oil bath method in this work and used in photocatalytic degradation of phenol. The optimal TOC removal rate reached up to 93.57% under illumination for 160 min, which was slightly lower than phenol photodegradation (about 100%, 100 min). Correspondingly, the apparent rate constants for the decay of phenol are determined to be 0.0211 min^-1. The experiment of free radical capture indicated that ·OH and ·O₂^- were the major oxidizing substances to degrade phenol. The products of phenol photodegradation were identified by high performance liquid chromatography (HPLC) and a possible degradation pathway was proposed. The characterization analysis and density functional theory (DFT) calculations demonstrated that dual S-scheme charge migration was generated at the interface of Bi₇O₉I₃, g-C₃N₄ and Bi₃O₄Cl, contributing to an efficient separation of light-excited carriers. In the field of environmental remediation, the discovery of this work could open up promising vistas for designing bismuth-based ternary heterostructures with application potentiality.

Recent advancements of g-C3N4-based magnetic photocatalysts towards the degradation of organic pollutants: a review

Heterogeneous photocatalysis premised on advanced oxidation processes has witnessed a broad application perspective, including water purification and environmental remediation. In particular, the graphitic carbon nitride (g-C₃N₄), an earth-abundant metal-free conjugated polymer, has acquired extensive application scope and interdisciplinary consideration owing to its outstanding structural and physicochemical properties. However, several issues such as the high recombination rate of the photo-generated electron-hole pairs, smaller specific surface area, and lower electrical conductivity curtail the catalytic efficacy of bulk g-C₃N₄. Another challenging task is separating the catalyst from the reaction medium, limiting their reusability and practical applications. Therefore, several methodologies are adopted strategically to tackle these issues. Attention is being paid, especially to the magnetic nanocomposites (NCs) based catalysts to enhance efficiency and proficient reusability property. This review summarizes the latest progress related to the design and development of magnetic g-C₃N₄-based NCs and their utilization in photocatalytic systems. The usefulness of the semiconductor heterojunctions on the catalytic activity, working mechanism, and degradation of pollutants are discussed in detail. The major challenges and prospects of using magnetic g-C₃N₄-based NCs for photocatalytic applications are highlighted in this report.

Sustainable materials in the removal of pesticides from contaminated water: Perspective on macro to nanoscale cellulose

Recently, over utilization of pesticides in agrarian and non- agrarian sectors has resulted in a significant increment in the deposition of their remnants in different segments of the environmental media. The presence of pesticides and transportation of their different metabolites in rivers, ponds, lakes, soils, air, groundwater sources and drinkable water sources has demonstrated a high threat to human wellbeing and the climate. Thus, the removal of pesticides and their metabolites from contaminated water is imperative to lessen the ill effects of pesticides on human beings. In the present article, we have appraised recent advances in pesticides removal utilizing low cost pristine and functionalized cellulose biomass-based derivatives. One of the key focus has been on better understand the destiny of pesticides in the environment as well as their behaviour in the water. In addition, the impact of magnetite cellulose nanocomposites, cellulose derived photo nano-catalyst, cellulose/clay nano composites, CdS/cellulose nanocomposites and activated carbons/biochar on percent removal of pesticides have also been a part of the current review. The impact of different parameters such as adsorbent dosage, pH, time of contact and initials pesticide concentration on adsorption capacity and adsorption kinetics followed during absorption by different cellulosic bio-adsorbents has also been given. The cellulosic biomass is highly efficient in the removal of pesticides and their efficiency further increases upon functionalization or their conversion into activated carbons forms. Nano particles loaded cellulosic materials have in general found to be less efficient than raw, functionalized cellulosic materials and activated carbons. Further, among different nano particles loaded with cellulose-based materials, cellulose/MnO₂ photonanocatalyst were noticed to be more effective. So considerable efforts should be given to determine the finest practices that relate to the dissipation of different pesticides from the water.

Synthesis of a plasmonic AgCl and oxygen-rich Bi24O31Cl10 composite heterogeneous catalyst for enhanced degradation of tetracycline and 2,4-dichlorophenoxy acetic acid

In this study, a AgCl/Bi24O31Cl10 composite heterostructure was constructed. Varying ratios of AgCl nanoparticles were immobilised onto the Bi24O31Cl10 rod-like structure. The physical and optical properties of the synthesised catalysts were characterised using a range of techniques. The photocatalytic activity of the catalysts was investigated by the degradation of 2,4-dichlorophenoxy acetic acid (2,4-D) and tetracycline (TC) under visible light irradiation. The performance of the composite photocatalysts was 18 and 3.4 times better in 2-4,D and TC photodegradation when compared to Bi24O31Cl10 alone. The improved photocatalytic performance was due to the surface plasmon resonance (SPR) effects of the Ag nanoparticles deposited on the surface of the Xwt%AgCl/BOC thereby improving the separation of the electron-hole pair. The effects of the initial contaminant concentration, pH, photocatalyst loading were investigated. Trapping experiments were also carried out to deduce the reactive species responsible for the degradation process and a preliminary mechanism of degradation was proposed. Successful mineralisation of 2,4-D and TC at 65% and 63% efficiency was also measured after 24 h and the potential for reusability of the as-synthesised photocatalyst was established. This work reports a promising heterogeneous photocatalyst for the removal of pollutants such as TC and 2,4-D from wastewater.

2D/2D Heterojunction systems for the removal of organic pollutants: A review

Photocatalysis is considered to be an effective way to remove organic pollutants, but the key to photocatalysis is finding a high-efficiency and stable photocatalyst. 2D materials-based heterojunction has aroused widespread concerns in photocatalysis because of its merits in more active sites, adjustable band gaps and shorter charge transfer distance. Among various 2D heterojunction systems, 2D/2D heterojunction with a face-to-face contact interface is regarded as a highly promising photocatalyst. Due to the strong coupling interface in 2D/2D heterojunction, the separation and migration of photoexcited electron-hole pairs are facilitated, which enhances the photocatalytic performance. Thus, the design of 2D/2D heterojunction can become a potential model for expanding the application of photocatalysis in the removal of organic pollutants. Herein, in this review, we first summarize the fundamental principles, classification, and strategies for elevating photocatalytic performance. Then, the synthesis and application of the 2D/2D heterojunction system for the removal of organic pollutants are discussed. Finally, the challenges and perspectives in 2D/2D heterojunction photocatalysts and their application for removing organic pollutants are presented.

4D Printing of Smart Polymer Nanocomposites: Integrating Graphene and Acrylate Based Shape Memory Polymers

The ever-increasing demand for materials to have superior properties and satisfy functions in the field of soft robotics and beyond has resulted in the advent of the new field of four-dimensional (4D) printing. The ability of these materials to respond to various stimuli inspires novel applications and opens several research possibilities. In this work, we report on the 4D printing of one such Shape Memory Polymer (SMP) tBA-co-DEGDA (tert-Butyl Acrylate with diethylene glycol diacrylate). The novelty lies in establishing the relationship between the various characteristic properties (tensile stress, surface roughness, recovery time, strain fixity, and glass transition temperature) concerning the fact that the print parameters of the laser pulse frequency and print speed are governed in the micro-stereolithography (Micro SLA) method. It is found that the sample printed with a speed of 90 mm/s and 110 pulses/s possessed the best batch of properties, with shape fixity percentages of about 86.3% and recovery times as low as 6.95 s. The samples built using the optimal parameters are further subjected to the addition of graphene nanoparticles, which further enhances all the mechanical and surface properties. It has been observed that the addition of 0.3 wt.% of graphene nanoparticles provides the best results.

Highly Effective Covalently Crosslinked Composite Alginate Cryogels for Cationic Dye Removal

Currently, macroporous hydrogels have been receiving attention in wastewater treatment due to their unique structures. As a natural polymer, alginate is used to remove cationic dyes due to its sustainable features such as abundance, low cost, processability, and being environmentally friendly. Herein, alginate/montmorillonite composite macroporous hydrogels (cryogels) with high porosity, mechanical elasticity, and high adsorption yield for methylene blue (MB) were generated by the one-step cryogelation technique. These cryogels were synthesized by adding montmorillonite into gel precursor, followed by chemical cross-linking employing carbodiimide chemistry in a frozen state. The as-prepared adsorbents were analyzed by FT-IR, SEM, gel fraction, swelling, uniaxial compression, and MB adsorption tests. The results indicated that alginate/montmorillonite cryogels exhibited high gelation yield (up to 80%), colossal water uptake capacity, elasticity, and effective dye adsorption capacity (93.7%). Maximum adsorption capacity against MB was 559.94 mg g^-1 by linear regression of Langmuir model onto experimental data. The Pseudo-Second-Order model was fitted better onto kinetic data compared to the Pseudo-First-Order model. Improved porosity and mechanical elasticity yielding enhanced dye removal capacity make them highly potential alternative adsorbents compared to available alginate/montmorillonite materials for MB removal.

Synthesis and Characterization of Novel Fe3O4/PVA/Eggshell Hybrid Nanocomposite for Photodegradation and Antibacterial Activity

In the 21st century, hybrid nanocomposites were widely used in bioelectronic, biosensing, photocatalytic, and biomedical applications. In the present study, we fabricated a novel Fe3O4/PVA/Eggshell hybrid nanocomposite and physicochemically characterized it using powder XRD, EDS, FTIR, VSM, and HR-TEM analysis. The XRD spectrum revealed the crystalline and FCC configuration of Fe3O4 NPs with average crystal size of 16.28 nm, and the HRTEM image indicates the prepared hybrid nanocomposite is of spherical shape with less agglomeration. This hybrid nanocomposite showed a significant photodegradation property in degrading organic pollutants such as congo red and crystal violet dyes under the sunlight irradiation. In addition, the hybrid nanocomposite also displayed a potent antibacterial property against different Gram +ve and Gram −ve bacterial pathogens. This study provides a significant example in the overview of fabrication of cost effectively, eco-friendly, and multiple-application hybrid nanocomposites through eggshell membrane fibers.

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.

Facile fabrication of AgI/Sb2O3 heterojunction photocatalyst with enhanced visible-light driven photocatalytic performance for efficient degradation of organic pollutants in water

The construction of heterojunction is considered as a promising approach to designing highly effective visible-light driven photocatalysts. In this research, the AgI/Sb₂O₃ heterojunction photocatalyst was synthesized by a simple in situ deposition-precipitation procedure, which was supported by XPS results. Among the prepared samples, the 60% AgI/Sb₂O₃ samples exhibited the best ARG degradation ratio (98.3%) in 1 h under visible light irradiation, while the pure Sb₂O₃ and AgI exhibited almost none photocatalytic performance. The trapping experiments and EPR proved that the photo-generated ·O₂^- and ·OH made major contributions to the photocatalytic degradation of ARG by the 60% AgI/Sb₂O₃ samples. The enhanced photocatalytic performance of AgI/Sb₂O₃ heterojunction photocatalysts was ascribed to that the e^- produced in the CB of AgI would be transferred to the empty CB of Sb₂O₃, which could effectively promote separation of photo-induced carries. More importantly, the transfer of electrons from AgI to Sb₂O₃ would be in favor of restraining the reduction of Ag⁺ to Ag⁰ resulting in the good stability of heterojunction photocatalysts. The heterojunction photocatalyst provided in this work might be a prospective candidate for decontamination of water.

Boosting light-driven CO2 reduction into solar fuels: Mainstream avenues for engineering ZnO-based photocatalysts

The realization of artificial photosynthesis in the photocatalytic CO₂ transformation into valuable chemicals or solar fuels, such as CO, CH₄, HCOOH, and CH₃OH, by solar-light harvesting is a promising solution to both global-warming and energy-supply issues. Recently, zinc oxide (ZnO) has emerged as an excellent oxidative photocatalyst among non-titanium metal oxides due to its availability, outstanding semiconducting and optical properties, non-toxicity, affordability, and ease of synthesis. However, ZnO wide bandgap and inability to absorb in the visible region has demanded particular modification for its practical use as a sustainable photocatalyst. This review provides a panorama of the latest advancement on ZnO photocatalysis for CO₂ reduction with an overview of fundamental aspects. Various modification strategies such as transition metal and non-metal doping, loading of plasmonic metals, and surface vacancy engineering for tunning the properties and improving the performance of ZnO are elaborated. Composites or hetero-structuralization-based Z-scheme formation is also presented along with a detailed photocatalytic reduction mechanism. Moreover, a new novel Step-scheme (S-scheme) heterostructure modification with a charge transfer pathway mechanism is also highlighted. Finally, the key challenges and new directions in this field are proposed to provide a new vision for further improvement for ZnO-based photocatalytic CO₂ conversion.

The room temperature synthesis of a CuO-Bi-BiOBr ternary Z-scheme photocatalyst for enhanced sunlight driven alcohol oxidation

The room temperature synthesis of an all-solid-state Z-scheme CuO-doped BiOBr (CuO-Bi-BiOBr) photocatalyst has been described. These CuO-Bi-BiOBr ternary heterojunctions exhibit efficient photocatalytic activities for selective alcohol oxidation. The structures, morphologies, and compositions of the nanostructures were well characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and atomic absorption spectroscopy (AAS). The X-ray diffraction (XRD) pattern of the as-synthesized nanostructures confirms the formation of phase-segregated CuO and BiOBr nanocrystals, whereas X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) analyses clearly indicate the formation of metallic bismuth nanoparticles (NPs). Next, the developed CuO-Bi-BiOBr ternary heterojunctions were applied as an efficient photocatalyst for the oxidation of alcohols into their corresponding aldehydes/ketones with high selectivity (>99%) and high conversion ratios (>99%). Herein, Bi metal NPs act as an electron mediator and bridge the connectivity between the two semiconductors, BiOBr and CuO, and, thus, a Z-scheme heterojunction is established. As expected, CuO-Bi-BiOBr has shown significantly superior activities compared to those of pure BiOBr. A possible mechanism for the photocatalytic oxidation process has been proposed. Radical scavenging experiments suggest that the active species, h⁺, ˙OH, e^-, and ˙O₂^-, are dominant in the alcohol oxidation process. The as-synthesized CuO-Bi-BiOBr was reused several times without any significant deterioration in the original activities and it thus possesses relatively high stability for practical applications.

Antibacterial and Antiviral Functional Materials: Chemistry and Biological Activity toward Tackling COVID-19-like Pandemics

The ongoing worldwide pandemic due to COVID-19 has created awareness toward ensuring best practices to avoid the spread of microorganisms. In this regard, the research on creating a surface which destroys or inhibits the adherence of microbial/viral entities has gained renewed interest. Although many research reports are available on the antibacterial materials or coatings, there is a relatively small amount of data available on the use of antiviral materials. However, with more research geared toward this area, new information is being added to the literature every day. The combination of antibacterial and antiviral chemical entities represents a potentially path-breaking intervention to mitigate the spread of disease-causing agents. In this review, we have surveyed antibacterial and antiviral materials of various classes such as small-molecule organics, synthetic and biodegradable polymers, silver, TiO2, and copper-derived chemicals. The surface protection mechanisms of the materials against the pathogen colonies are discussed in detail, which highlights the key differences that could determine the parameters that would govern the future development of advanced antibacterial and antiviral materials and surfaces.