Visible light activated TiO2/microcrystalline cellulose nanocatalyst to destroy organic contaminants in water

Nano/micro-cellulose-based materials as remarkable sorbents for the remediation of agricultural resources from chemical pollutants

Overusing pesticides, fertilizers, and synthetic dyes has significantly increased their presence in various parts of the environment. The transportation of these pollutants into agricultural soil and water through rivers, soils, and groundwater has seriously threatened human and ecosystem health. Applying techniques and materials to clean up agricultural sources from pesticides, heavy metals (HMs), and synthetic dyes (SDs) is one of the major challenges in this century. The sorption technique offers a viable solution to remediate these chemical pollutants (CHPs). Cellulose-based materials have become popular in nano and micro scales because they are widely available, safe to use, biodegradable, and have a significant ability to absorb substances. Nanoscale cellulose-based materials exhibit greater capacity in absorbing pollutants compared to their microscale counterparts because they possess a larger surface area. Many available hydroxyl groups (-OH) and chemical and physical modifications enable the incorporation of CHPs on to cellulose-based materials. Following this potential, this review aims to comprehensively summarize recent advancements in the field of nano- and micro-cellulose-based materials as effective adsorbents for CHPs, given the abundance of cellulosic waste materials from agricultural residues. The recent developments pertaining to the enhancement of the sorption capacity of cellulose-based materials against pesticides, HMs, and SDs, are deliberated.

TiO2/g-C3N4/SO3H(IL): Unique Usage of Ionic Liquid-Based Sulfonic Acid as an Efficient Photocatalyst for Visible-Light-Driven Preparation of 5-HMF from Cellulose and Glucose

Upgrading of biomass wastes to value-added materials has been incessantly pursued worldwide with diverse applications, especially deploying photocatalytic composites encompassing metal oxides with acidic and carbon compounds. Herein, the fabrication of a morphologically unique acidic catalyst encompassing a two-dimensional (2D) TiO₂/g-C₃N₄ heterojunction feature is described for the generation of 5-hydroxymethylfurfural (5-HMF), which exploits the acidic/ionic liquid (IL) bifunctional photocatalysis under visible light. The structural integrity of the synthesized TiO₂/g-C₃N₄/SO₃H(IL) was corroborated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy-energy-dispersive spectroscopy (EDX-EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), UV-vis, Tauc plots, transmission electron microscopy (TEM), and Brunauer-Emmett-Teller-Barrett-Joyner-Halenda (BET-BJH) analyses. Keeping environmental impact in mind, there are compelling advantages in the development of bio-derived pathways to access ILs from natural renewable resources. The outcomes of environmental assessments have revealed that the incorporation of TiO₂ in g-C₃N₄ and ClSO₃H can reduce the probability of recombination due to ionic charges present, therefore enhancing the photocatalytic activity via the transformation of cellulose and glucose to produce 5-HMF in higher yields, with the optimum conditions being reaction in water under a blue light-emitting diode (LED), at 100 °C, for 1-1.5 h. The main advantages of this production method include minimum number of synthetic steps as well as ample availability of and easy access to primary ingredients. While a significant volume of 5-HMF was produced under blue light-emitting diode (LED) radiation, the selectivity was drastically reduced in the dark. The salient attributes of the catalyst comprise stability in air, robustness, reusability, and its overall superior activity that is devoid of hazardous additives or agents. This inimitable method has uncovered a newer strategy for enhancing the photocatalytic attributes of deployed semiconducting materials for numerous photocatalytic functions while adhering to the tenets of environmental friendliness.

Highly-Efficient and Visible Light Photocatalytical Degradation of Organic Pollutants Using TiO2-Loaded on Low-Cost Biomass Husk

A composite composing of TiO₂ nanoparticles load on biomass rice husk (RH) is developed by directly growing TiO₂ nanoparticles on RH. The in-situ growth of the nanocrystals on RH is achieved by a low-cost and one-step homogeneous precipitation. Rapid hydrolysis proceeds at 90 °C by using ammonium fluotitanate and urea to facilitate the selective growth of TiO₂. The method provides an easy access to the TiO₂-RH composite with a strong interaction between TiO₂ nanoparticles and the underlying RH. The structure and composition of TiO₂-RH are characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and UV-vis absorption spectroscopy. TiO₂ nanoparticles-RH exhibits a good photocatalytic degradation of methyl orange. The results show that 92% of methyl orange (20 mg L^-1) can be degraded within three hours in visible light. The catalytic activity of the composite is not reduced after 6 cycles, and it still reaches 81% after 6 cycles. The enhanced performance is ascribed to the suitable particle size the good dispersibility. It is expected that the high photocatalytical performance and the cost-effective composite presented here will inspire the development of other high-performance photocatalysts.

Designing novel MgFe2O4 coupled V2O5 nanorod for synergetic photodegradation of tetracycline with enhanced visible-light energy harvesting: Photoluminescence, kinetics, intrinsic mechanism and bactericidal effect

The present study focused on the enhancement of degradation of an important pharmaceutical pollutant, tetracycline with the help of nano photocatalyst under visible light irradiation. The study found that the synergetic effect of novel MgFe₂O₄-V₂O₅ enhanced the photocatalytic degradation of tetracycline. Here, the photocatalyst was synthesized by sonochemical technique. Scanning electron microscopy image indicates the coupling of MgFe₂O₄ nanocapsules on the surface of the V₂O₅ nanorod. The bandgap of MgFe₂O₄ (1.8 eV) and V₂O₅ (2.5 eV) was shifted to 2.32 eV in MgFe₂O₄-V₂O₅ to promote visible-light harvesting and it was depicted by the UV-visible DRS. XPS was used to identify the presence of chemical states with the existence of Mg 1s, Fe 2p, V 2p, and O 1s. The electrochemical impedance spectroscopy and photoluminescence spectra indicate the better separation of charge carriers owing to the formation of type II heterojunction formation. The tetracycline (25 mg/L) was degraded with MgFe₂O₄-V₂O₅ (150 mg/L) that exhibited 3.3 and 5 folds enhanced rates than its counterparts (MgFe₂O₄ and V₂O₅) owing to synergism. The possible intermediate formation and degradation pathway was determined based on GC/MS analysis. TOC analysis of end products indicated maximum mineralization of tetracycline. The MgFe₂O₄-V₂O₅ showed excellent recycling ability and reusability. The key photo-degradation of tetracycline was occurred by the generation of hydroxyl radicals. The MgFe₂O₄-V₂O₅ exhibited high antibacterial activity that ensures the dual functionality of the prepared nanocomposites (NCs). Therefore, the present study displays MgFe₂O₄ decorated V₂O₅ nanorod as an ideal candidate for environmental remediation.

Guar gum based nanocomposites: Role in water purification through efficient removal of dyes and metal ions

Researchers nowadays are relentlessly on a race exploring sustainable materials and techniques for the sequestration of toxic dyes and metal ions from water bodies. Biopolymers such as guar gum, owing to its high abundance, low cost and non-toxicity, are potential candidates in this field. Plenty of hydroxyl groups in the polymer backbone enable guar gum to be functionalised or grafted in a versatile manner proving itself as an excellent starting substance for fabricating upgraded materials meant for diverse applications. This review offers a comprehensive coverage of the role of guar gum-based nanocomposites in removal of dyes and heavy metal ions from waste water through adsorption and photo-catalytic degradation. Isotherm and kinetics models, fabrication routes, characterisation techniques, swelling properties and reusability as well as adsorption and degradation mechanisms are outlined. A detailed analysis with convincing results suggests a good future perspective of implementation of these materials in real-time wastewater treatment technology.

Adsorption-photocatalysis performance of polyaniline/dicarboxyl acid cellulose@graphene oxide for dye removal

A novel 3-D biopolymer-based adsorption-photocatalytic composite, polyaniline/dicarboxyl acid cellulose@graphene oxide was synthesized and was employed to remove the reactive brilliant red K-2G from aqueous solution. The addition of dicarboxyl acid cellulose could improve the morphology, structure, stability and dispersity of the nanocomposite, thus providing excellent adsorption and photocatalysis performance to the product. Batch of experiments were conducted in two scenarios: adsorption followed by photocatalysis process and simultaneous adsorption-photocatalysis process. For the first scenario, adsorption equilibrium can be reached within 25 min, the expected adsorption capacity was 447.0 mg·g^-1; the subsequent photocatalysis process was carried out under light irradiation and the removal capacity could further improve to 729.0 mg·g^-1 under equilibrium state (about 180 min). For the simultaneous adsorption-photocatalytic process, the removal capacity was about 558.1 mg·g^-1 at about 25 min and the total removal capacity could reach to 733.3 mg·g^-1 under equilibrium state. PANI-DCC@GO exhibited excellent reusability and had potential in the treatment of dyes polluted wastewater.

Transparent Microcrystalline Cellulose/Polyvinyl Alcohol Paper as a New Platform for Three-Dimensional Cell Culture

Multilayered and stacked cellulose paper has emerged as a promising platform for construction of three-dimensional (3D) cell culture because of its low cost, good biocompatibility, and high porosity. However, its poor light transmission makes it challenging to directly and clearly monitor cell behaviors (e.g., growth and proliferation) on the paper-based platform using an optical microscope. In this work, we developed a transparent microcrystalline cellulose/polyvinyl alcohol (MCC/PVA) paper with irregular pores through dissolution and regeneration of microcrystalline nanocellulose, addition of a porogen reagent (NaCl), and subsequently dipping in PVA solutions. The transparent MCC paper displays high porosity (up to 90%), adjustable pore size (between 23 and 46 μm), large thickness (from 315 to 436 μm), and high light transmission under water (>95%). Through further modification of the transparent MCC paper with PVA, the obtained transparent MCC/PVA paper shows enhanced mechanical properties (dry and wet strengths), good hydrophilicity (with a contact angle of 70.8°), and improved biocompatibility (cell viability up to 90%). By stacking and destacking multiple layers of the transparent MCC/PVA paper, it has been used for both two-dimensional and three-dimensional cell culture platforms. The transparent MCC/PVA paper under water enables both direct observation of cell morphology by an optical microscope via naked eyes and fluorescence microscope after staining. We envision that the developed transparent MCC/PVA paper holds great potential for future applications in various bioanalytical and biomedical fields, such as drug screening, tissue engineering, and organ-on-chips.

Sol-gel synthesis of carbon-doped TiO2 nanoparticles based on microcrystalline cellulose for efficient photocatalytic degradation of methylene blue under visible light

Carbon-doped titanium dioxide photocatalyst with improved performance in visible light was prepared via the typical sol-gel method. Microcrystalline cellulose (MCC) was used as carbon elements source. The prepared pure and carbon-doped TiO₂ samples were calcined at 400-650°C in air and the effect of annealing temperature on the stability of carbon ions was investigated. EDX analysis showed the presence of 5.66 wt.% carbon atoms in TiO₂ nanoparticles formed on MCC, which was attributed to the doping of carbon atoms in TiO₂ lattice. Carbon doping was also confirmed by Raman spectroscopy. According to the UV-VIS DRS analysis, the band gap of TiO₂ particles decreased from 2.96 to 2.71 eV in pure and carbon-doped TiO₂, respectively. Therefore the visible light absorbance increased to 15.05% compared to 0% absorbance in pure TiO₂. The heat treatment of carbon-doped TiO₂ nanostructures showed that carbon element could escape from the O-Ti-O lattice at temperatures higher than 600°C. According to the SEM images, synthesis of TiO₂ in presence of MCC also limited the growth of TiO₂ nanoparticles and controlled the morphology and aggregation of nanoparticles. Carbon doping improved the photocatalytic performance of TiO₂ photocatalyst compared to the pure nanoparticles in degradation of methylene blue in the aqueous phase. Carbon-doped TiO₂ attained the efficiency of 56.25%, 51.18% and 62.95% under UV, visible and solar lights, respectively, compared to 28.43%, 6.36% and 33.65% related to the pure TiO₂.

Cellulose particles capture aldehyde VOC pollutants

Aldehydes are commonly encountered Volatile Organic Compounds (VOCs) released to the atmosphere from a variety of anthropogenic sources. Based on the increasing interest in developing sustainable and environmentally friendly materials for the decontamination of VOCs, cellulose particles have emerged as one possible candidate, but there is a lack of understanding of the physicochemical properties affecting the adsorption of VOCs, and the effect of the extraction source on these intrinsic features. The present study was focused on the evaluation of unmodified cellulose particles extracted from biodiverse sources in Ecuador as potential VOC decontaminants. Modifications of the natural fibers with polyethylenimine (PEI) coating were performed to enhance the adsorption effectiveness. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) measurements, and scanning electron microscopy (SEM) methods were used to characterize the physicochemical properties of the isolates. Gas chromatography assays demonstrated that unmodified cellulose can adsorb an aldehyde VOC, hexanal, reaching up to a 56.42 ± 7.30% reduction. Electrostatic coating of the cellulose particles with small quantities of PEI enhanced the VOC remediation capacities (i.e. 98.12 ± 1.18%). Results demonstrated that the biodiverse plant source of the cellulose isolate can affect the gas capturing properties, and that these particles can be an environmentally friendly solution for effective adsorption of VOC pollutants.

Cellulose particles isolated from biodiverse sources are capable of capturing aldehyde VOCs.

Nanostructured Metal Catalysts for Selective Hydrogenation and Oxidation of Cellulosic Biomass to Chemicals

Conversion of biomass to chemicals provides essential products to human society from renewable resources. In this context, achieving atom-economical and energy-efficient conversion with high selectivity towards target products remains a key challenge. Recent developments in nanostructured catalysts address this challenge reporting remarkable performances in shape and morphology dependent catalysis by metals on nano scale in energy and environmental applications. In this review, most recent advances in synthesis of heterogeneous nanomaterials, surface characterization and catalytic performances for hydrogenation and oxidation for biorenewables with plausible mechanism have been discussed. The perspectives obtained from this review paper will provide insights into rational design of active, selective and stable catalytic materials for sustainable production of value-added chemicals from biomass resources.

Lignin-Based Composite Materials for Photocatalysis and Photovoltaics

Depleting conventional fuel reserves has prompted the demand for the exploration of renewable resources. Biomass is a widely available renewable resource that can be valorized to produce fuels, chemicals, and materials. Among all the fractions of biomass, lignin has been underutilized. Due to its complex structure, recalcitrant nature, and heterogeneity, its valorization is relatively challenging. This review focuses on the utilization of lignin for the preparation of composite materials and their application in the field of photocatalysis and photovoltaics. Lignin can be used as a photocatalyst support for its potential application in photodegradation of contaminants. The interaction between the components in hybrid photocatalysts plays a significant role in determining the photocatalytic performance. The application of lignin as a photocatalyst support tends to control the size of the particles and allows uniform distribution of the particles that influence the characteristics of the photocatalyst. Lignin as a semiconductive polymer dopant for photoanodes in photovoltaic cells can improve the photoconversion efficiency of the cell. Recent success in the development of lignosulfonates dopant for hole transport materials in photovoltaics will pave the way for further research in lignin-based high-performance organic electronic devices.

Visible light-assisted efficient degradation of dye pollutants with biomass-supported TiO2 hybrids

The objective of this work was to develop a novel organic-inorganic hybrid nanomaterial from agricultural biomass waste for environmental applications. The sugarcane bagasse (SB) supported TiO₂ hybrids were firstly synthesized via a sol-gel method. A series of characterizations were carried out to reveal the structures and components of obtained hybrids. Due to organic-inorganic hybrid (OIH) effect and element doping, the SB-TiO₂ hybrid can expand its optical absorbance ranging from ultraviolet to visible light. The optimal hybrid catalyst prepared with SB doping amount of 2g in 100mL titanic gel and calcined at 200°C was able to degradate 95.0% methyl orange (MO) in 5h under visible light. This study will pave a new and facile pathway for novel visible light driven photocatalysts based on TiO₂ modified by agricultural biomass waste.

An overview on cellulose-based material in tailoring bio-hybrid nanostructured photocatalysts for water treatment and renewable energy applications

A combination between the nanostructured photocatalyst and cellulose-based materials promotes a new functionality of cellulose towards the development of new bio-hybrid materials for various applications especially in water treatment and renewable energy. The excellent compatibility and association between nanostructured photocatalyst and cellulose-based materials was induced by bio-combability and high hydrophilicity of the cellulose components. The electron rich hydroxyl group of celluloses helps to promote superior interaction with photocatalyst. The formation of bio-hybrid nanostructured are attaining huge interest nowadays due to the synergistic properties of individual cellulose-based material and photocatalyst nanoparticles. Therefore, in this review we introduce some cellulose-based material and discusses its compatibility with nanostructured photocatalyst in terms of physical and chemical properties. In addition, we gather information and evidence on the fabrication techniques of cellulose-based hybrid nanostructured photocatalyst and its recent application in the field of water treatment and renewable energy.

Sustainable hybrid photocatalysts: titania immobilized on carbon materials derived from renewable and biodegradable resources

This review comprises the preparation, properties and heterogeneous photocatalytic applications of TiO2 immobilized on carbon materials derived from earth-abundant, renewable and biodegradable agricultural residues and sea food waste resources. The overview provides key scientific insights into widely used TiO2 supported on carbonaceous materials emanating from biopolymeric materials such as lignin, cellulose, cellulose acetate, bacterial cellulose, bamboo, wood, starch, chitosan and agricultural residues (biochar, charcoal, activated carbon and their magnetic forms, coal fly ash) or seafood wastes namely eggshell, clamshell and fish scales; materials that serve as a support/template for TiO2. Heightened awareness and future inspirational developments for the valorisation of various forms of carbonaceous functional materials is the main objective. This appraisal abridges various strategies available to upgrade renewable carbon-based feedstock via the generation of sustainable TiO2/carbon functional materials and provides remarks on their future prospects. Hopefully, this will stimulate the development of efficient and novel composite photocatalysts and engender the necessary knowledge base for further advancements in greener photocatalytic technologies.

Cellulose: A review as natural, modified and activated carbon adsorbent

Cellulose is a biodegradable, renewable, non-meltable polymer which is insoluble in most solvents due to hydrogen bonding and crystallinity. Natural cellulose shows lower adsorption capacity as compared to modified cellulose and its capacity can be enhanced by modification usually by chemicals. This review focuses on the utilization of cellulose as an adsorbent in natural/modified form or as a precursor for activated carbon (AC) for adsorbing substances from water. The literature revealed that cellulose can be a promising precursor for production of activated carbon with appreciable surface area (∼1300m(2)g(-1)) and total pore volume (∼0.6cm(3)g(-1)) and the surface area and pore volume varies with the cellulose content. Finally, the purpose of review is to report a few controversies and unresolved questions concerning the preparation/properties of ACs from cellulose and to make aware to readers that there is still considerable scope for future development, characterization and utilization of ACs from cellulose.

One-pot synthesis of MnO2-chitin hybrids for effective removal of methylene blue

Manganese dioxide (MnO₂)-chitin-hybrid material was prepared by a facile "one-pot" synthesis method. MnO₂-chitin hybrid was used for the effective removal of methylene blue (MB) from liquid solution as model for wastewater treatment. The hybrid obtained was characterized by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analysis. The effect of pH and temperature were studied. MnO₂-chitin hybrid showed high performance for oxidative decolorization and removal of MB. Typically, 25mL of MB (20mg/L) can be completely decolorized in 2.5min with 8.5mg of the MnO₂-chitin hybrid. The hybrid material exhibited excellent recyclability and durability with the degradation value of 99% for MB after ten consecutive cycles.

Efficient removal of rhodamine 6G dye from aqueous solution using nickel sulphide incorporated polyacrylamide grafted gum karaya bionanocomposite hydrogel

This research paper reports the synthesis and usage of the polyacrylamide (PAAm) grafted gum karaya (Gk) and nickel sulphide nanoparticle based hydrogel to effectively remove rhodamine 6G dye (R6G) from aqueous solution.