Facile synthesis of chitosan-La3+-graphite composite and its influence in photocatalytic degradation of methylene blue

RSM approach for process optimization of the photodegradation of congo red by a novel NiCo2S4/chitosan photocatalyst

The current study reported a facile co-precipitation technique for synthesizing novel NiCo2S4/chitosan nanocomposite. The photocatalytic activity of the prepared nanocomposite was evaluated using congo red (CR) dye as a target pollutant. The central composite design was employed to examine the impact of different reaction conditions on CR dye degradation. This study selected the pH, photocatalyst loading, initial CR concentration and reaction time as reaction parameters, while the degradation efficiency (%) was selected as the response. A desirability factor of 1 suggested the adequacy of the model. Maximum degradation of 93.46% of 35 ppm dye solution was observed after 60 min of visible light irradiation. The response to surface methodology (RSM) is a helpful technique to predict the optimum reaction conditions of the photodegradation of CR dye. Moreover, NiCo2S4/Ch displayed high recyclability and reusability up to four consecutive cycles. The present study suggests that the prepared NiCo2S4/chitosan nanocomposite could prove to be a viable photocatalyst for the treatment of dye-contaminated wastewater.

Double-function ZnO/starch biodegradable hydrogel composite for methylene blue adsorption and photocatalytic degradation

An eco-friendly material for the removal of dyes from wastewater was developed. Biodegradable polymers (BP), cassava starch and poly(vinyl alcohol), were used to replace polyacrylamide. The hydrogel containing 50 wt% of BP (BP50) could absorb 34 times its dry weight of water. The hydrogel could adsorb Zn2+ and ZnO photocatalyst particles could be formed via a simple precipitation method. The incorporation of ZnO did not affect the adsorption efficiency of the ZnO/BP50 hydrogel composite towards methylene blue (MB). At initial concentrations (Co) below 4500 mg/g, the hydrogel composite removed ∼99 % of MB from solution in 3 h. The highest adsorption capacity of 1170 mg/g was obtained when Co was 6000 mg/g and at a dose of 0.10 g/20 mL. The hydrogel composite degraded 95 %-98 % of adsorbed MB at rates of 0.19 h-1 and 1.77 h-1 under UV irradiation and sunlight, respectively, with exposure times of 16 h for UV but only 2 h for sunlight. The material remained effective for at least 10 cycles of photodegradation under sunlight and removed 86 % of MB in solution on the 10th cycle. The composite also showed antibacterial activities and biodegradability in soil. These results indicated this material would not generate after-process toxic waste.

Metal/metal oxide-carbohydrate polymers framework for industrial and biological applications: Current advancements and future directions

Recently, the development and consumption of metal/metal oxide carbohydrate polymer nanocomposites (M/MOCPNs) are withdrawing significant attention because of their numerous salient features. Metal/metal oxide carbohydrate polymer nanocomposites are being used as environmentally friendly alternatives for traditional metal/metal oxide carbohydrate polymer nanocomposites exhibit variable properties that make them excellent prospects for a variety of biological and industrial uses. In metal/metal oxide carbohydrate polymer nanocomposites, carbohydrate polymers bind with metallic atoms and ions using coordination bonding in which heteroatoms of polar functional groups behave as adsorption centers. Metal/metal oxide carbohydrate polymer nanocomposites are widely used in woundhealing, additional biological uses and drug delivery, heavy ions removal or metal decontamination, and dye removal. The present review article features the collection of some major biological and industrial applications of metal/metal oxide carbohydrate polymer nanocomposites. The binding affinity of carbohydrate polymers with metal atoms and ions in metal/metal oxide carbohydrate polymer nanocomposites has also been described.

Enhanced removal of methylene blue from wastewater by alginate/carboxymethyl cellulose-melamine sponge composite

Industrial dye wastewater poses a threat to human health due to its harmful effects, and the treatment of related wastewater is receiving increasing attention. In this paper, the melamine sponge with high porosity and convenient separation was selected as matrix material, and alginate/carboxymethyl cellulose-melamine sponge composite (SA/CMC-MeS) was prepared through crosslinking strategy. Not only does the composite cleverly combined the merits of alginate and carboxymethyl cellulose, it also enhanced the adsorption performance for methylene blue (MB). The adsorption data manifested that the adsorption process of SA/CMC-MeS agreed with the Langmuir model and pseudo-second-order kinetic model, and theoretical maximum adsorption capacity was 230 mg/g (pH 8). The characterization results demonstrated that the adsorption mechanism was attributed to the electrostatic attraction between the carboxyl anions on the composite and the dye cations in solution. Importantly, SA/CMC-MeS could selectively separate MB from binary dye system and had positive anti-interference ability in the face of coexisting cations. After 5 times of cycles, the adsorption efficiency remained above 75 %. Based on these outstanding practical properties, this material has a potential to solve dye contamination.

Ag/Ag2O with NIR-Triggered Antibacterial Activities: Photocatalytic Sterilization Enhanced by Low-Temperature Photothermal Effect

Purpose

A synergistic antibacterial system employing photocatalytic performance and low-temperature photothermal effect (LT-PTT) with the potential for infectious skin wound healing promotion was developed.

Methods

Ag/Ag₂O was synthesized with a two-step method, and its physicochemical properties were characterized. After its photocatalytic performance and photothermal effect were evaluated under 0.5 W/cm² 808 nm NIR laser irradiation, its antibacterial activities in both planktonic and biofilm forms were then studied in vitro targeting Staphylococcus Aureus (S. aureus), and the biocompatibility was tested with L-929 cell lines afterward. Finally, the animal model of dorsal skin wound infection was established on Sprague-Dawley rats and was used to assess infectious wound healing promotion of Ag/Ag₂O in vivo.

Results

Ag/Ag₂O showed boosted photocatalytic performance and local temperature accumulation compared with Ag₂O when exposed to 0.5 W/cm² 808 nm NIR irradiation, which therefore endowed Ag/Ag₂O with the ability to kill pathogens rapidly and cleavage bacterial biofilm in vitro. Furthermore, after treatment with Ag/Ag₂O and 0.5 W/cm² 808 nm NIR irradiation, infectious wounds of rats realized skin tissue regeneration from a histochemical level.

Conclusion

By exhibiting excellent NIR-triggered photocatalytic sterilization ability enhanced by low-temperature photothermal effect, Ag/Ag₂O was promising to be a novel, photo-responsive antibacterial agent.

Evaluation of the multifunctional activity of silver bionanocomposites in environmental remediation and inhibition of the growth of multidrug-resistant pathogens

Imperata cylindrica cellulose supported Ag bionanocomposites purified industrial water and controlled the contagious diseases with high potential activity.

Photocatalytic dye degradation and photoexcited anti-microbial activities of green zinc oxide nanoparticles synthesized via Sargassum muticum extracts

Drug-resistant superbugs (DRS) were isolated from hospital sewage waste and confirmed by a 16S rDNA molecular technique as B. filamentosus, B. flexus, P. stutzeri, and A. baumannii. Green nanotechnologies provide a new promising alternative pathway that was found to be much safer, eco-friendly, and has economic benefits over physical/chemical methods. Sargassum muticum (SM) mediated zinc oxide nanoparticles (ZnO-NPs) were proved to be photocatalytic and anti-microbial agents. Anti-microbial action was demonstrated by a maximal growth inhibition activity of 18 mm against A. baumannii and a minimal of 12 mm against B. flexus at 80 μg mL-1 concentrations. The anti-microbial mechanism of SMZnO-NPs employed a biphasic phenomenon persuaded by an osmotic shock that can attack the DRS bacterial cells directly and lead to death. In addition, photocatalytic activity was investigated by SMZnO-NPs for the degradation of methylene blue (MB) dye under different light conditions. Natural sunlight irradiation shows effective enhancement with the highest efficiencies of 96% being achieved within 60 min compared to UV-light and visible-light. The reusability of SMZnO-NPs provides up to 6 consecutive cycles towards MB decolorization for environmental water cleansing.

Applications of chitin and chitosan based biomaterials for the adsorptive removal of textile dyes from water - A comprehensive review

The presence of pollutants in the water bodies deteriorate the water quality and make it unfit for use. From an environmental perspective, it is essential to develop new technologies for the wastewater treatment and recycling of dye contaminated water. The surface modified chitin and chitosan biopolymeric composites based adsorbents, have an important role in the toxic organic dyes from removal wastewater. The surface modification of biopolymers with various organics and inorganics produces more active sites at the surface of the adsorbent, which enhances dye and adsorbent interaction more reliable. Herein, the work brought in the thought of the application of various chitin and chitosan composites in wastewater remediation and suggested the versatility in composites for the development of rapid, selective and effective removal processes for the detoxification of a variety of organic dyes. It further emphasizes the existing obstruction and impending prediction for the deprivation of dyes via adsorption techniques.

Nanobiocatalysts and photocatalyst in dye degradation

In the modern era, the world today is in a mission for a new method of environmental bioremediation in faltering the damage, especially in polluted water. Recently, the global direction is regulated toward an alteration from the usual chemical-based methods to a supplementary ecofriendly green alternative. In this perspective, biocatalysts are appreciated as an economical and clean substitute which was meant to catalyze degradation of unmanageable chemicals in a rapid, green and ecologically stable manner. Among the various sources of water pollution, the textile manufacturing industries were thought to be a major dispute due to release of effluents in natural water bodies such as rivers. Other industries like paper, pulp and tannery pharmaceutical industries were also responsible in contaminating the water bodies. Photocatalysis was considered as an auspicious method for the removal of dyes from the natural bodies, specifically those with hard organic compounds; using enzymes. The present chapter briefly emphasizes on the effective methods used for degradation of dye effluents; their importance of photocatalytic and biocatalytic solution to the current environmental difficulties and future opportunities are discussed.

Ecofriendly biopolymers and composites: Preparation and their applications in water-treatment

Over the past few decades, the term polymer has been repeatedly used in several industries for their immense characteristics in different applications. Polymers and their composites which were prepared from chemical monomer sources turned out to be potentially harmful to the environment due to their tedious degradation process. Biopolymers are natural substitutes for synthetic polymers which can be efficiently extricated from natural sources. They are predominantly available as polymeric units as well as monomeric units that are linked covalently. These environment-friendly biopolymers and their composites can be categorized based on their numerous sources, different methods of preparation and their potential form of usage. They were found to be biocompatible and biodegradable which make them exceptionally useful in environment based applications, mainly in the process of water treatment, both potable and wastewater. Further, the biopolymer and biopolymer composites easily fit into different parts of the treatment process by acting as filtration media, adsorbents, coagulants and as flocculants. The primary focus of this review is to provide a comprehensive information of biopolymers and biopolymer composites from synthesis to their usefulness for their productive application in water treatment processes. On the whole, it can be substantiated that the biopolymers were identified to play a notable adversary to the synthetic polymers in treating waters with an indispensable need for an elaborative study in the production of the biopolymers.

Photocatalytic performance of chitosan tethered magnetic Fe2O3-like (3D/2D) hybrid for the dynamic removal of anionic dyes: Degradation and mechanistic pathways

Efficient photocatalysis methods with a production of less number of toxic intermediates are extremely advantageous for water decontamination. The degradation efficiency, specific surface area, stability and porosity will be improving by wrapping of Fe₂O₃ using appropriate biopolymers. In this work, Fe₂O₃ reinforced chitosan (Fe₂O₃@CS) nanocomposite was fabricated using co-precipitation method. The chitosan makes available its surface for the useful generation of the nanocomposite. These wrapping of Fe₂O₃ on chitosan provides synergistically improved properties that could be attributed to the elevated partition efficiency and faster transfer of the photo-generated charge carriers, which was substantiated by the experimental outcomes from photoluminescence and ESR spectroscopy. The results obtained from DRS analysis entail the reduction in band gap of Fe₂O₃@CS (2.52 eV) as compared with 3.52 eV of Fe₂O₃. The results indicated that 89.2% and 94.6% were the maximum degradations correspondingly for MO and OG. The trapping investigation emphasized the involvement of OH radicals in the degradation of dyes over Fe₂O₃@CS composites. The five cycles of regeneration experiment recommended the superior photostability of the fabricated Fe₂O₃@CS composite. This work proposed a practical arrangement and subsequent influence of an advanced photocatalyst for the useful remediation dyes from contaminated water without causing any secondary pollution.

Photocatalytic degradation of 2,4-dicholorophenoxyacetic acid by TiO2 modified catalyst: kinetics and operating cost analysis

Effective pesticide remediation technology demands amendments in the advanced oxidation process for its continuous treatment and catalyst recovery. The evidence of 2,4-dichlorophenoxyacetic acid (2,4-D), an herbicide in water bodies, poses a major environmental threat to both humans and aquatic organisms. In the present study, a recirculation type photocatalytic reactor was developed to treat 2,4-dichlorophenoxyacetic acid using chitosan-TiO2 beads prepared via impregnation method under UV light. At optimized conditions, chitosan-TiO2 beads showed a maximum photocatalytic degradation of 86% than commercial TiO2 (65%) and followed pseudo first-order reaction. The 2,4-D degradation follows pseudo first-order kinetics under UV irradiation with a rate constant of 0.12 h-1, and the intermediates were identified using LCMS analysis. The total operational cost of the chitosan-TiO2 catalyst was found to be profitable (Rs. 1323 for 2 L) than that of TiO2 (Rs. 1679) at optimized conditions. The beads were reusable up to 4 consecutive cycles without loss in efficiency. This study briefs photocatalytic removal of 2,4-dichlorophenoxyacetic acid in a recirculation-type reactor for its reliability, low cost, efficiency, reusability, and commercialization.

Biomaterial (Garlic and Chitosan)-Doped WO3-TiO2 Hybrid Nanocomposites: Their Solar Light Photocatalytic and Antibacterial Activities

In this work, WO₃-TiO₂, chitosan-blended WO₃-TiO₂, and garlic-loaded WO₃-TiO₂ nanocomposites were synthesized by the sol-gel and precipitation technique. The synthesized nanocomposites were characterized by XRD, FE-SEM, HR-TEM, EDX, UV-DRS, FT-IR, and TG-DTA analysis. The photocatalytic efficiency of the three synthesized nanocomposites on the degradation of dyes such as rhodamine B (Rh-B), methylene blue (MB), and methyl orange (MO) as organic pollutants was evaluated under solar light irradiation. The results show that garlic-loaded WO₃-TiO₂ nanocomposites act as an excellent photocatalyst than chitosan-blended WO₃-TiO₂ and WO₃-TiO₂ nanocomposites. Further, the antimicrobial activity of the synthesized nanocomposites was examined against Gram-negative bacteria (Escherichia coli) by the well diffusion method. Garlic-loaded WO₃-doped TiO₂ nanocomposites have demonstrated good antibacterial activity over chitosan-blended WO₃-TiO₂ nanocomposites and WO₃-TiO₂ nanocomposites. The possible reason may be the presence of organic sulfur compounds in garlic.

Integrating adsorption and photocatalysis: A cost effective strategy for textile wastewater treatment using hybrid biochar-TiO2 composite

TiO₂ based photocatalysts are extensively used for textile wastewater treatment as they are ecofriendly, inexpensive, easily available, nontoxic and have higher photostabililty. However, their wider band gap, charge carrier's recombination, and utilization of light absorbance limits their performance. In the present work, a hybrid biochar-TiO₂ composite (BCT) has been synthesized by a facile synthesis strategy to overcome these problems. These photocatalysts are characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), UV-vis diffuse reflectance spectra (DRS), and photoluminescence (PL) to evaluate their crystallinity, morphology, functional groups, bandgap energy and charge separation properties, respectively. The photodegradation of simulated textile wastewater is analyzed using hybrid composites. The hybrid biochar-TiO₂ composite showed higher charge separation, slow recombination of electron-hole pairs, and enhanced light absorption as compared to control (pure TiO₂ and BC alone). 99.20 % photodegradation efficiency of dye-simulated wastewater is achieved employing optimum hybrid composite, while the pure biochar and TiO₂ samples exhibits 85.20 % and 42.60 % efficiencies, respectively. The maximum adsorption capacity is obtained for hybrid biochar-TiO₂ sample, 74.30 mgg^-1 in comparison to biochar (30.40 mgg^-1) and pure TiO₂ (1.50 mgg^-1). The results show that hybrid biochar-TiO₂ composites can perform in the target application of organic industrial pollutant removal.

Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review

Due to the wonderful property of hydrogels, they can provide a platform for a wide range of applications. Recently, there is a growing research interest in the development of potential hydrogel adsorbents in wastewater treatment due to their adsorption ability toward aqueous pollutants. It is important to prepare such a hydrogel that possesses appropriate robustness, adsorption capacity, and adsorption efficiency to meet the need of water treatment. In order to improve the property of hydrogels, much effort has been made by researchers to modify hydrogels, among which incorporating inorganic components into the polymeric networks is the most common method, which can reduce the product cost and simplify the preparation procedure. Not only can hydrogel be applied as adsorbent, but it also can be used as matrix for catalyst immobilization. In this review, the key advancement on the preparation and modification of hydrogels is discussed, with special emphasis on the introduction of inorganic materials into polymeric networks and consequential changes in the properties of mechanical strength, swelling, and adsorption. Besides, hydrogels used as adsorbents for removal of dyes and inorganic pollutants have been widely explored, but their use for adsorbing emerging contaminants from aqueous solution has not received much attention. Thus, this review is mainly focused on hydrogels' application in removing emerging contaminants by adsorption. Furthermore, hydrogels can be also applied in immobilizing catalysts, such as enzyme and photocatalyst, to remove pollutants completely and avoid secondary pollution, so their progress as catalyst matrix is overviewed.

Green polymeric nanomaterials for the photocatalytic degradation of dyes: a review

Pure and drinkable water will be rarer and more expensive as the result of pollution induced by industrialisation, urbanisation and population growth. Among the numerous sources of water pollution, the textile industry has become a major issue because effluents containing dyes are often released in natural water bodies. For instance, about two years are needed to biodegrade dye-derived, carcinogenic aromatic amines, in sediments. Classical remediation methods based upon physicochemical reactions are costly and still generate sludges that contain amine residues. Nonetheless, recent research shows that nanomaterials containing biopolymers are promising to degrade organic pollutants by photocatalysis. Here, we review the synthesis and applications of biopolymeric nanomaterials for photocatalytic degradation of azo dyes. We focus on conducting biopolymers incorporating metal, metal oxide, metal/metal oxide and metal sulphide for improved biodegradation. Biopolymers can be obtained from microorganisms, plants and animals. Unlike fossil-fuel-derived polymers, biopolymers are carbon neutral and thus sustainable in the context of global warming. Biopolymers are often biodegradable and biocompatible.