Boosting antibacterial efficiency of gelatin/chitosan composite films through synergistic interaction of ag nanoparticles and ZIF-8 metal-organic frameworks for food packaging

The main challenge in the food packaging industry is preventing food spoilage caused by pathogens and microorganisms, which requires the development of effective antibacterial materials to improve food safety and extend shelf life. To address this issue, a nanocomposite, AgNPs@ZIF-8@CMC, consisting of silver nanoparticles (AgNPs), zeolitic imidazolate framework-8 (ZIF-8), and carboxymethyl cellulose (CMC) using an environmentally friendly, DMF-free process was synthesized. Various concentrations of AgNPs@ZIF-8@CMC were incorporated into gelatin/chitosan films via the solution casting method. The synergistic effects of silver and zinc ions, combined with the high surface area of the porous composite, significantly contributed to its antimicrobial activity. AgNPs@ZIF-8@CMC demonstrated remarkable antibacterial properties, producing inhibition zones of 22 ± 0.6 mm and 20 ± 0.6 mm against E. coli and S. aureus, respectively.Incorporating the nanocomposite into gelatin and chitosan films significantly increased the inhibition zones, from 0 mm to 30 ± 1 mm for S. aureus and from 0 mm to 28 ± 1.15 mm for E. coli. Notably, 4 % (AgNPs@ZIF-8@CMC)-Gel/Chi and 1 % (AgNPs@ZIF-8@CMC)-Gel/Chi composite films eliminated E. coli and S. aureus within 3 h, respectively. This research emphasizes the considerable potential of synthesized composite films as active packaging materials for preserving perishable fruits.

Production of probiotic bacterial cellulose with improved yield, mechanical properties, and antibacterial activity from cost-effective coculture and mixed-culture fermentation in coconut water by Komagataeibacter xylinus MSKU 12

We successfully enhanced bacterial cellulose (BC) production in low-cost coconut water (CW) at 37 °C by low-nutrient adaptation of Komagataeibacter xylinus MSKU 12. In this study, the BC yield was significantly increased by simultaneous coculture fermentation of MSKU 12 with Saccharomyces bayanus in Hestrin-Schramm (HS) and CW media. Coculture fermentation at 30 °C produced BC yields of 13.44 and 12.13 g/L dry weight in HS containing 0.5 % acetic acid, 3 % sucrose, and 0.5 % ammonium sulfate (HS0.5A3S0.5N) after 9 days of incubation and in CW containing 0.5 % acetic acid, 3 % sucrose, and 0.5 % ammonium sulfate (CW0.5A3S0.5N) after 12 days of incubation. Moreover, at 37 °C, relatively high amounts of BC (8.64 and 7.89 g/L dry weight) were obtained from coculture in HS0.5A3S0.5N and CW0.5A3S0.5N, respectively, after 12 days of cultivation. Coculture fermentation not only increased the BC yield but also altered the properties of BC, resulting in finer microfibrils, higher mechanical strength, and stronger antibacterial activities. Both fresh and freeze-dried probiotic BC from the simultaneous mixed-culture fermentation of MSKU 12, S. bayanus, and Pediococcus pentosaceus DMKU 14-7 exhibited strong inhibitory effects against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. These results provided insights into the development of biopreservatives against foodborne pathogens.

Recent development towards the novel applications and future prospects for cellulose-metal organic framework hybrid materials: a review

The hybrid material created by combining cellulose and MOF is highly promising and possesses a wide range of useful properties. Cellulose-based metal-organic frameworks (CelloMOFs) combine the inherent biocompatibility and sustainability of cellulose with the tunable porosity and diverse metal coordination chemistry of MOFs. Cellulose-MOF hybrids have countless applications in various fields, such as energy storage, water treatment, air filtration, gas adsorption, catalysis, and biomedicine. They are particularly remarkable as adsorbents that can eliminate pollutants from wastewater, including metals, oils, dyes, antibiotics, and drugs, and act as catalysts for oxidation and reduction reactions. Furthermore, they are highly efficient air filters, able to remove carbon dioxide, particulate matter, and volatile organic compounds. When it comes to energy storage, these hybrids have demonstrated exceptional results. They are also highly versatile in the realm of biomedicine, with applications such as antibacterial and drug delivery. This article provides an in-depth look at the fabrication methods, advanced applications of cellulose-MOF hybrids, and existing and future challenges.

Fabrication of Loose Nanofiltration Membrane by Crosslinking TEMPO-Oxidized Cellulose Nanofibers for Effective Dye/Salt Separation

Dye/salt separation has gained increasing attention in recent years, prompting the quest to find cost-effective and environmentally friendly raw materials for synthesizing high performance nanofiltration (NF) membrane for effective dye/salt separation. Herein, a high-performance loose-structured NF membrane was fabricated via a simple vacuum filtration method using a green nanomaterial, 2,2,6,6-tetramethylpiperidine-1-oxide radical (TEMPO)-oxidized cellulose nanofiber (TOCNF), by sequentially filtrating larger-sized and finer-sized TOCNFs on a microporous substrate, followed by crosslinking with trimesoyl chloride. The resulting TCM membrane possessed a separating layer composed entirely of pure TOCNF, eliminating the need for other polymer or nanomaterial additives. TCM membranes exhibit high performance and effective dye/salt selectivity. Scanning Electron Microscope (SEM) analysis shows that the TCM membrane with the Fine-TOCNF layer has a tight layered structure. Further characterizations via Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) confirmed the presence of functional groups and chemical bonds of the crosslinked membrane. Notably, the optimized TCM-5 membrane exhibits a rejection rate of over 99% for various dyes (Congo red and orange yellow) and 14.2% for NaCl, showcasing a potential candidate for efficient dye wastewater treatment.

Recent progress and applications of cellulose and its derivatives-based humidity sensors: A review

Cellulose and its derivatives, which are low-cost, degradable, reproducible and highly hydrophilic, can serve as both substrate and humidity sensitive materials, making them more and more popular as ideal biomimetic materials for humidity sensors. Benefiting from these characteristics, cellulose-based humidity sensors cannot only exhibit high sensitivity, excellent mechanical performance, wide humidity response range, etc., but also can be applied to fields such as human health, medical care and agricultural product safety monitoring. Herein, cellulose-based humidity sensors are first classified according to the different conductive active materials, such as carbon nanotubes, graphene, electrolytes, metal compounds, and polymer materials, based on which the latest research progress is introduced, and the roles of different types of conductive materials in cellulose-based humidity sensors are analyzed and summarized. Besides, the similarities and differences in their working mechanisms are expounded. Finally, the application scenarios of cellulose-based humidity sensors in human movement respiration and skin surface humidity monitoring are discussed, which can make readers quickly familiarize the current preparation method, working mechanism and subsequent development trend of cellulose-based humidity sensors more effectively.

Cation-exchange performance of a citric-acid esterified cellulose nanofibrous membrane for highly-selective proteins' permeability and adsorption capacity

The usage of low-cost, readily available, or even disposable, single-use membranes in macromolecules' purification and separation is still in the development phase. In this research, highly porous (>95 %), water- and compression stable cation-exchange membranes were prepared by freeze-casting using cellulose nanofibrils (CNF) and citric acid (CA) acting as a crosslinker and source of weak anionic (carboxylic) surface groups arising from the mono-esterified CA. The membranes were characterized by different analytical techniques, and evaluated for the ionic adsorption efficacy of different proteins in dead-end filtration mode using a Tri-buffer of pH 8. The membrane's internal microstructure (porosity and density) with the available (quantity and access) carboxylic groups was confirmed, to determine not only the proteins' specific (related to the net charged and molecular weight) adsorption dynamic (>52 % of positive Lysozyme/Cytochrome, <8 % of negative BSA/Myoglobin; ≤0.5 g/L) at extremely high flow rates (>3.000 hL/h*MPa*m2), but also their desorption (>97 %) and re-equilibration (using NaCl) with flux recovery (>80 %). Such efficiency was achieved with up to 5 consecutive filtering cycles. The high permeability (>87 %) of the spherical and negatively surface charged microparticles (used as models) also suggests the likelihood of removing larger microbial species, which, while retaining relatively smaller and positively charged proteins, further increases their potential in biopharma applications.

Polymeric Materials Obtained by Extrusion and Injection Molding from Lignocellulosic Agroindustrial Biomass

This review presents the advances in polymeric materials achieved by extrusion and injection molding from lignocellulosic agroindustrial biomass. Biomass, which is derived from agricultural and industrial waste, is a renewable and abundant feedstock that contains mainly cellulose, hemicellulose, and lignin. To improve the properties and functions of polymeric materials, cellulose is subjected to a variety of modifications. The most common modifications are surface modification, grafting, chemical procedures, and molecule chemical grafting. Injection molding and extrusion technologies are crucial in shaping and manufacturing polymer composites, with precise control over the process and material selection. Furthermore, injection molding involves four phases: plasticization, injection, cooling, and ejection, with a focus on energy efficiency. Fundamental aspects of an injection molding machine, such as the motor, hopper, heating units, nozzle, and clamping unit, are discussed. Extrusion technology, commonly used as a preliminary step to injection molding, presents challenges regarding fiber reinforcement and stress accumulation, while lignin-based polymeric materials are challenging due to their hydrophobicity. The diverse applications of these biodegradable materials include automotive industries, construction, food packaging, and various consumer goods. Polymeric materials are positioned to offer even bigger contributions to sustainable and eco-friendly solutions in the future, as research and development continues.

Unveiling the interactions between biomaterials and heterocyclic dyes: A sustainable approach for wastewater treatment

The present Review investigates the interactions between biomaterials and heterocyclic dyes, focusing on their potential application in sustainable wastewater treatment. Heterocyclic dyes are widely used in various industries, resulting in their widespread presence in wastewater, posing environmental challenges. This review explores the utilization of biomaterials as adsorbents for the removal of heterocyclic dyes from contaminated water sources. The interactions between biomaterials, such as cellulose, microfibrilated cellulose and lignin and different heterocyclic dyes are examined through reported experimental analysis and characterization techniques. The study evaluates the adsorption capacity, kinetics, and thermodynamics of the biomaterial-dye systems to elucidate the underlying mechanisms and optimize the treatment process. The review highlight the promising potential of biomaterial-based approaches for sustainable wastewater treatment, providing insights for the development of efficient and environmentally friendly dye removal technologies.

Fabrication and Characterization of Magnetic Cellulose-Chitosan-Alginate Composite Hydrogel Bead Bio-Sorbent

The implementation of inorganic adsorbents for the removal of heavy metals from industrial effluents generates secondary waste. Therefore, scientists and environmentalists are looking for environmentally friendly adsorbents isolated from biobased materials for the efficient removal of heavy metals from industrial effluents. This study aimed to fabricate and characterize an environmentally friendly composite bio-sorbent as an initiative toward greener environmental remediation technology. The properties of cellulose, chitosan, magnetite, and alginate were exploited to fabricate a composite hydrogel bead. The cross linking and encapsulation of cellulose, chitosan, alginate, and magnetite in hydrogel beads were successfully conducted through a facile method without any chemicals used during the synthesis. Energy-dispersive X-ray analysis verified the presence of element signals of N, Ca, and Fe on the surface of the composite bio-sorbents. The appearance and peak's shifting at 3330-3060 cm^-1 in the Fourier transform infrared spectroscopy analysis of the composite cellulose-magnetite-alginate, chitosan-magnetite-alginate, and cellulose-chitosan-magnetite-alginate suggested that there are overlaps of O-H and N-H and weak interaction of hydrogen bonding with the Fe₃O₄ particles. Material degradation, % mass loss, and thermal stability of the material and synthesized composite hydrogel beads were determined through thermogravimetric analysis. The onset temperature of the composite cellulose-magnetite-alginate, chitosan-magnetite-alginate, and cellulose-chitosan-magnetite-alginate hydrogel beads were observed to be lower compared to raw-material cellulose and chitosan, which could be due to the formation of weak hydrogen bonding resulting from the addition of magnetite Fe₃O₄. The higher mass residual of cellulose-magnetite-alginate (33.46%), chitosan-magnetite-alginate (37.09%), and cellulose-chitosan-magnetite-alginate (34.40%) compared to cellulose (10.94%) and chitosan (30.82%) after degradation at a temperature of 700 °C shows that the synthesized composite hydrogel beads possess better thermal stability, owing to the addition of magnetite and the encapsulation in the alginate hydrogel beads.

Metal-organic frameworks/cellulose hybrids with their modern technological implementation towards water treatment

Metal-organic frameworks (MOFs) are amongst the most attractive porous polymeric networks with appealing properties. However, their inherent fragility, powder nature, low processibility, and handling present some exceptional challenges for high-tech commercial applications. Currently, economic and environmental concerns drive the development of some bioinspired polymeric matrices containing MOFs. As an artifact, the availability of previously unattainable properties is negotiated by conjugating cellulosic materials with crystalline MOFs. Thus, multi-dimensional organic-inorganic hybrid composites are formed with high electrical, optical, mechanical, and thermal features. These MOF/cellulose hybrids, known as CelloMOFs (cellulose MOFs), have remarkable mechanical properties with tunable porosities, specific surface area and accessible active sites, making them ideal for real-world troubleshooting applications such as wastewater treatment, chemical sensing, energy storage, and so on. In this review, current state-of-the-art strategic synthesis routes for fabrication of MOF/cellulose composites with a specific focus on CelloMOFs as a potential tool for mitigation of the targeted emerging water contaminants have been done under the same umbrella, which has previously been less explored. Streamlining discussions on general properties such as raw material selection, structural analysis of cellulose, availability of surface functional groups, cellulose-metal node interactions, cellulose charging, and so on have been emphasized, as has integration with robust MOFs. A better understanding of these fundamental properties is critical because they will have a significant impact on the performance of MOF/cellulose composites in a variety of applications. Furthermore, at the end of this review, the challenges and perspectives of using CelloMOFs have been discussed in a concise manner in order to improve their practical utility rather than just concept mapping.

Efficient Isolation Method for Highly Charged Phosphorylated Cellulose Nanocrystals

Phosphorylation of cellulose nanocrystals (CNCs) has remained a marginal activity despite the undisputed application potential in flame-retardant materials, sustainable high-capacity ion-exchange materials, or substrates for biomineralization among others. This is largely due to strenuous extraction methods prone to a combination of poor reproducibility, low degrees of substitution, disappointing yields, and impractical reaction sequences. Here, we demonstrate an improved methodology relying on the modification routines for phosphorylated cellulose nanofibers and hydrolysis by gaseous HCl to isolate CNCs. This allows us to overcome the aforementioned shortcomings and to reliably and reproducibly extract phosphorylated CNCs with exceptionally high surface charge (∼2000 mmol/kg) in a straightforward routine that minimizes water consumption and maximizes yields. The CNCs were characterized by NMR, ζpotential, conductometric titration, thermogravimetry, elemental analysis, wide-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy.

Understanding Nanocellulose-Water Interactions: Turning a Detriment into an Asset

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose-water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

Properties of bacterial cellulose acetate nanocomposite with TiO2 nanoparticle and graphene reinforcement

Agricultural waste is considered a promising source for bacterial cellulose production. This study aims to observe the influence of TiO₂ nanoparticles and graphene on the characteristic of bacterial cellulose acetate-based nanocomposite membranes for bacterial filtration in waters. Bacterial cellulose was produced from the pineapple peel waste using fermentation process. High-pressure homogenization process was applied to reduce bacterial nanocellulose size and esterification process was carried out to produce cellulose acetate. Nanocomposite membranes were synthesized with reinforcement of TiO₂ nanoparticles 1 % and graphene nanopowder 1 %. The nanocomposite membrane was characterized using an FTIR, SEM, XRD, BET, tensile testing, and bacterial filtration effectiveness using the plate count method. The results showed that the main cellulose structure was identified at the diffraction angle 22° and the cellulose structure slightly changed at the peak of diffraction angles of 14° and 16°. In addition, the crystallinity of bacterial cellulose increased from 72.5 % to 75.9 %, and the functional group analysis showed that several peak shifts indicated a change in the functional group of membrane. Similarly, the surface morphology of membrane became rougher with the structure of mesoporous membrane. Moreover, adding TiO₂ and graphene increases crystallinity and bacterial filtration effectiveness of nanocomposite membrane.

Agricultural Residues as Raw Materials for Pulp and Paper Production: Overview and Applications on Membrane Fabrication

The need for pulp and paper has risen significantly due to exponential population growth, industrialization, and urbanization. Most paper manufacturing industries use wood fibers to meet pulp and paper requirements. The shortage of fibrous wood resources and increased deforestation are linked to the excessive dependence on wood for pulp and paper production. Therefore, non-wood substitutes, including corn stalks, sugarcane bagasse, wheat, and rice straw, cotton stalks, and others, may greatly alleviate the shortage of raw materials used to make pulp and paper. Non-woody raw materials can be pulped easily using soda/soda-AQ (anthraquinone), organosolv, and bio-pulping. The use of agricultural residues can also play a pivotal role in the development of polymeric membranes separating different molecular weight cut-off molecules from a variety of feedstocks in industries. These membranes range in applications from water purification to medicinal uses. Considering that some farmers still burn agricultural residues on the fields, resulting in significant air pollution and health issues, the use of agricultural residues in paper manufacturing can eventually help these producers to get better financial outcomes from the grown crop. This paper reviews the current trends in the technological pitch of pulp and paper production from agricultural residues using different pulping methods, with an insight into the application of membranes developed from lignocellulosic materials.

Foaming of oxidized nanocellulose for the preparation of high-flux water filters

Treatment of polluted water is an important task to secure access to clean water also for future generations. Filters are an efficient means to reject various pollutants on a wide range of size scales either by size-exclusion or electrostatic interaction, respectively. Commonly, filters and membranes from various synthetic materials are employed for these applications. Recently, filters based on renewable (nano) cellulose papers and coatings emerged as sustainable alternative to synthetic materials usually utilized. However, fabrication of such paper network structures from aqueous suspension by filtration processes is a time-consuming process caused by the high water holding capacity of highly hydrophilic and negatively charged nanocellulose fibrils. To optimize the preparation of nanocellulose coated filters, substitution of water by air and thus generating nanocellulose foams that are collapsed onto a substrate would be an appealing approach. Here we present the development of foams from negatively charged TEMPO-oxidized nanocellulose by screening various surfactants and concentrations to generate a foam stable enough to be transferred onto a viscose substrate. Foams were collapsed by oven consolidation, positive pressure filtration, or hot-pressing, respectively. Consolidated filters were tested for their water permeance and rejection of heavy metal ions using copper ions as model system. Very high permeances competitive to commercial filters based on synthetic polymers were achieved. Furthermore, adsorption capacities for copper of up to 70 mg/g were found. This is close to adsorption capacities reported for negatively charged TEMPO-oxidized nanocellulose in conventional batch-wise static adsorption. However, in the current process adsorption takes place during filtration of water through filters in a continuous process which constitutes a tremendous advantage.

Graphical Abstract

Recent advances and future perspective on nanocellulose-based materials in diverse water treatment applications

Over the past few years, nanocellulose and its derivatives have drawn attention as promising bio-based materials for water treatment applications due to their high surface area, high strength, and renewable, biocompatible nature. The abundance of hydroxyl functional groups on the surfaces of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) enables a broad range of surface modifications which results in propitious nanocomposites with tunable characteristics. In this context, this review describes the continuously developing applications of nanocellulose-based materials in the areas of adsorption, catalysis, filtration, and flocculation, with a special emphasis on the removal of contaminants such as heavy metals, dyes, and pharmaceutical compounds from diverse water systems. Recent progresses in the diverse forms of application of nanocellulose adsorbents (suspension, hydrogel, aerogel, and membrane) are also highlighted. Finally, challenges and future perspectives on emerging nanocellulose-based materials and their possible industrial applications are presented and discussed.

Enhanced removal of Eriochrome Black T from water using biochar/layered double hydroxide/chitosan hybrid composite: Performance evaluation and optimization using BBD-RSM approach

In this research work, a novel hybrid composite consisting of biochar (B), layered double hydroxide (CuFe) and chitosan (CS) (B-CuFe-CS) was produced using an ultrasonication-assisted co-precipitation method. The resultant composite was employed for adsorptive removal of Eriochrome black T (EBT) from water. Physicochemical characterization indicated that the B-CuFe-CS containing 10 wt % CS exhibited a heterogeneous structure with better crystallographic and textural characteristics. The B-CuFe-CS with abundant surface functionalities (-CO, -C-O, -OH, -NO_3, and MMO), facilitates faster and enhanced removal of the EBT. The kinetic results showed better fitting to the pseudo-second order model, and equilibrium was achieved within 30 min. Equilibrium data was well explained by Langmuir and Redlich Peterson isotherm models (R² > 0.98), indicating the EBT removal onto B-CuFe-CS followed monolayer adsorption. The maximum adsorption capacity was 806.4 mg/g, which was higher than pristine B-CuFe (476.19 mg/g) and many other adsorbents. The spectroscopic analysis (FTIR and XPS) and experimental results suggested that EBT adsorption is mainly governed by electrostatic, chemical and anion-exchange interactions. It is evident from these results that coupling B-CuFe composite with bio-filler (chitosan) resulted in an efficient bio-adsorbent to effectively purify dye-contaminated water streams.

Carboxymethyl Cellulose/Zn-Organic Framework Down-Regulates Proliferation and Up-Regulates Apoptosis and DNA Damage in Colon and Lung Cancer Cell Lines

A solvothermal technique was used to prepare a Zn-benzenetricarboxylic acid (Zn@BTC) organic framework covered with a carboxymethyl cellulose (CMC/Zn@BTC). Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and Brunauer, Emmett, and Teller (BET) surface area were applied to characterize CMC/Zn@BTC. Moreover, the anticancer, anti-migrative, anti-invasive, and anti-proliferative action of CMC/Zn@BTC nanoparticles were assessed on cancer cell lines. Apoptotic markers and DNA damage were assessed to explore the cellular and biological changes induced by CMC/Zn@BTC nanoparticles. The microscopic observation revealed that CMC controls the surface morphology and surface characteristics of the Zn@BTC. The obtained BET data revealed that the Zn@BTC nanocomposite surface area lowers from 1061 m2/g to 740 m2/g, and the pore volume decreases from 0.50 cm3/g to 0.37 cm3/g when CMC is applied to Zn@BTC nanocomposites. The cellular growth of DLD1 and A549 was suppressed by CMC/Zn@BTC, with IC50 values of 19.1 and 23.1 μg/mL, respectively. P53 expression was upregulated, and Bcl-2 expression was downregulated by CMC/Zn@BTC, which promoted the apoptotic process. Furthermore, CMC/Zn@BTC caused DNA damage in both cancer cell lines with diverse impact, 66 percent (A549) and 20 percent (DLD1) compared to cisplatin's 52 percent reduction. CMC/Zn@BTC has anti-invasive properties and significantly reduced cellular migration. Moreover, CMC/Zn@BTC aims key proteins associated with metastasis, proliferation and programmed cellular death.

Nanocellulose for Sustainable Water Purification

Nanocelluloses (NC) are nature-based sustainable biomaterials, which not only possess cellulosic properties but also have the important hallmarks of nanomaterials, such as large surface area, versatile reactive sites or functionalities, and scaffolding stability to host inorganic nanoparticles. This class of nanomaterials offers new opportunities for a broad spectrum of applications for clean water production that were once thought impractical. This Review covers substantial discussions based on evaluative judgments of the recent literature and technical advancements in the fields of coagulation/flocculation, adsorption, photocatalysis, and membrane filtration for water decontamination through proper understanding of fundamental knowledge of NC, such as purity, crystallinity, surface chemistry and charge, suspension rheology, morphology, mechanical properties, and film stability. To supplement these, discussions on low-cost and scalable NC extraction, new characterizations including solution small-angle X-ray scattering evaluation, and structure-property relationships of NC are also reviewed. Identifying knowledge gaps and drawing perspectives could generate guidance to overcome uncertainties associated with the adaptation of NC-enabled water purification technologies. Furthermore, the topics of simultaneous removal of multipollutants disposal and proper handling of post/spent NC are discussed. We believe NC-enabled remediation nanomaterials can be integrated into a broad range of water treatments, greatly improving the cost-effectiveness and sustainability of water purification.

Lignocellulosic Biomass-Derived Nanocellulose Crystals as Fillers in Membranes for Water and Wastewater Treatment: A Review

The improvement of membrane applications for wastewater treatment has been a focal point of research in recent times, with a wide variety of efforts being made to enhance the performance, integrity and environmental friendliness of the existing membrane materials. Cellulose nanocrystals (CNCs) are sustainable nanomaterials derived from microorganisms and plants with promising potential in wastewater treatment. Cellulose nanomaterials offer a satisfactory alternative to other environmentally harmful nanomaterials. However, only a few review articles on this important field are available in the open literature, especially in membrane applications for wastewater treatment. This review briefly highlights the circular economy of waste lignocellulosic biomass and the isolation of CNCs from waste lignocellulosic biomass for membrane applications. The surface chemical functionalization technique for the preparation of CNC-based materials with the desired functional groups and properties is outlined. Recent uses of CNC-based materials in membrane applications for wastewater treatment are presented. In addition, the assessment of the environmental impacts of CNCs, cellulose extraction, the production techniques of cellulose products, cellulose product utilization, and their end-of-life disposal are briefly discussed. Furthermore, the challenges and prospects for the development of CNC from waste biomass for application in wastewater treatment are discussed extensively. Finally, this review unraveled some important perceptions on the prospects of CNC-based materials, especially in membrane applications for the treatment of wastewater.

Recent Development and Environmental Applications of Nanocellulose-Based Membranes

Extensive research and development in the production of nanocellulose production, a green, bio-based, and renewable biomaterial has paved the way for the development of advanced functional materials for a multitude of applications. From a membrane technology perspective, the exceptional mechanical strength, high crystallinity, tunable surface chemistry, and anti-fouling behavior of nanocellulose, manifested from its structural and nanodimensional properties are particularly attractive. Thus, an opportunity has emerged to exploit these features to develop nanocellulose-based membranes for environmental applications. This review provides insights into the prospect of nanocellulose as a matrix or as an additive to enhance membrane performance in water filtration, environmental remediation, and the development of pollutant sensors and energy devices, focusing on the most recent progress from 2017 to 2022. A brief overview of the strategies to tailor the nanocellulose surface chemistry for the effective removal of specific pollutants and nanocellulose-based membrane fabrication approaches are also presented. The major challenges and future directions associated with the environmental applications of nanocellulose-based membranes are put into perspective, with primary emphasis on advanced multifunctional membranes.

Cellulose Nanomaterials as a Future, Sustainable and Renewable Material

Cellulose nanomaterials (CNs) are renewable, bio-derived materials that can address not only technological challenges but also social impacts. This ability results from their unique properties, for example, high mechanical strength, high degree of crystallinity, biodegradable, tunable shape, size, and functional surface chemistry. This minireview provides chemical and physical features of cellulose nanomaterials and recent developments as an adsorbent and an antimicrobial material generated from bio-renewable sources.

Application of polysaccharide-based metal organic framework membranes in separation science

Polysaccharide/MOF composite membranes have captured the interests of many researchers during decontamination of polluted environments. Their popularity can be attributed to the relatively high chemical and thermal stabilities of these composite membranes. Chitosan is among the polysaccharides extensively used during the synthesis of hybrid membranes with MOFs. The applications of chitosan/MOF composite membranes in separation science are explored in detail in this paper. Researchers have also synthesised mixed matrix membranes of MOFs with cellulose and cyclodextrin that have proved to be effective during separation of a variety of materials. The uses of cellulose/MOF and cyclodextrin/MOF membranes for the removal of environmental pollutants are discussed in this review. In addition, the challenges associated with the use of these mixed matrix membranes are explored in this current paper.

Nanocellulose-Based Materials for Water Treatment: Adsorption, Photocatalytic Degradation, Disinfection, Antifouling, and Nanofiltration

Nanocelluloses are promising bio-nano-materials for use as water treatment materials in environmental protection and remediation. Over the past decades, they have been integrated via novel nanoengineering approaches for water treatment processes. This review aims at giving an overview of nanocellulose requirements concerning emerging nanotechnologies of waster treatments and purification, i.e., adsorption, absorption, flocculation, photocatalytic degradation, disinfection, antifouling, ultrafiltration, nanofiltration, and reverse osmosis. Firstly, the nanocellulose synthesis methods (mechanical, physical, chemical, and biological), unique properties (sizes, geometries, and surface chemistry) were presented and their use for capturing and removal of wastewater pollutants was explained. Secondly, different chemical modification approaches surface functionalization (with functional groups, polymers, and nanoparticles) for enhancing the surface chemistry of the nanocellulose for enabling the effective removal of specific pollutants (suspended particles, microorganisms, hazardous metals ions, organic dyes, drugs, pesticides fertilizers, and oils) were highlighted. Thirdly, new fabrication approaches (solution casting, thermal treatment, electrospinning, 3D printing) that integrated nanocelluloses (spherical nanoparticles, nanowhiskers, nanofibers) to produce water treatment materials (individual composite nanoparticles, hydrogels, aerogels, sponges, membranes, and nanopapers) were covered. Finally, the major challenges and future perspectives concerning the applications of nanocellulose based materials in water treatment and purification were highlighted.

Nanocellulose-Graphene Derivative Hybrids: Advanced Structure-Based Functionality from Top-down Synthesis to Bottom-up Assembly

There is an emerging endeavor of advanced structure-based functionality in the next-generation advanced functional materials inspired by hierarchical architecture for future technical applications. This review provides an impressive range roadmap for constructing advanced functional materials based on the nanocellulose-graphene derivative hybrids, from the top-down synthesis of their hierarchical materials to the bottom-up assembly of their nanoscale building blocks. First, the roadmap started from the top-down synthesis routes of nanocellulose-graphene hierarchical materials into their derivatives, where the pristine properties of nanoscale building blocks are still accessible and processable. Then, the stable-strong synergistic interfacial interactions between nanocellulose chains and graphene derivative nanosheets are uniquely well-suited in this roadmap for constructing scalable hybrid materials with interesting emergent properties. After that, the roadmap presented the bottom-up assembly approaches of these versatile nanoscale building blocks through self-assembly, templating, and mimicking of the bioinspired hierarchical structures toward advanced functional materials. Thereafter, toward understanding the specificity, superiority, and functionality of such hybrid materials, the roadmap discussed the properties and potential applications so far. Finally, the roadmap pointed out the key challenges and future outlooks, paving the way for comprehensive understanding and ideal designing of hybrid structures from nanocellulose and graphene derivatives.

TEMPO-oxidised nanocellulose hydrogels and self-standing films derived from bacterial cellulose nanopaper

Hydrogels derived from TEMPO-oxidised cellulose nanofibrils (TOCNs) are not robust and inherently water unstable if the TOCNs are not crosslinked or coated with a water-swellable polymer. Furthermore, the manufacturing of self-standing TOCN films is still a challenge due to the small TOCN diameter and the viscosifying effect of TOCNs. Here, we report the TEMPO-mediated oxidation of bacterial cellulose (BC) nanopaper as a route to produce robust and water stable TOCN hydrogels without the need of additional additives or crosslinking steps. Pristine BC pellicle was first press-dried into a dried and well-consolidated BC nanopaper, followed by TEMPO-oxidation at various NaClO concentrations. The oxidation reaction introduced carboxylate moieties onto the exposed BC nanofibrils within the nanopaper network structure. This then led to the expansion and swelling of the nanopaper into a hydrogel. A swelling ratio of up to 100 times the original thickness of the BC nanopaper was observed upon TEMPO-oxidation. The water retention value of the TEMPO-oxidised BC hydrogels was also found to increase with increasing carboxylate content. These TEMPO-oxidised BC hydrogels were found to be robust and water-stable, even under prolonged (>1 month) magnetic stirring in water. We further showed that high grammage self-standing TOCN films (100 g m-2) can be fabricated as simple as press-drying these water stable TEMPO-oxidised BC hydrogels without the need of vacuum-assisted filtration or slow-drying, which is typically the rate-limiting step in the manufacturing of TOCN films.

Recent Advances in the Synthesis of Nanocellulose Functionalized–Hybrid Membranes and Application in Water Quality Improvement

The increasing discharge of voluminous non or partially treated wastewaters characterized by complex contaminants poses significant ecological and health risks. Particularly, this practice impacts negatively on socio-economic, technological, industrial, and agricultural development. Therefore, effective control of water pollution is imperative. Over the past decade, membrane filtration has been established as an effective and commercially attractive technology for the separation and purification of water. The performance of membrane-based technologies relies on the intrinsic properties of the membrane barrier itself. As a result, the development of innovative techniques for the preparation of highly efficient membranes has received remarkable attention. Moreover, growing concerns related to cost-effective and greener technologies have induced the need for eco-friendly, renewable, biodegradable, and sustainable source materials for membrane fabrication. Recently, advances in nanotechnology have led to the development of new high-tech nanomaterials from natural polymers (e.g., cellulose) for the preparation of environmentally benign nanocomposite membranes. The synthesis of nanocomposite membranes using nanocelluloses (NCs) has become a prominent research field. This is attributed to the exceptional characteristics of these nanomaterials (NMs) namely; excellent and tuneable surface chemistry, high mechanical strength, low-cost, biodegradability, biocompatibility, and renewability. For this purpose, the current paper opens with a comprehensive yet concise description of the various types of NCs and their most broadly utilized production techniques. This is closely followed by a critical review of how NC substrates and their surface-modified versions affect the performance of the fabricated NC-based membranes in various filtration processes. Finally, the most recent processing technologies for the preparation of functionalized NCs-based composite membranes are discussed in detail and their hybrid characteristics relevant to membrane filtration processes are highlighted.

Biodegradable gelatin composite hydrogels filled with cellulose for chromium (VI) adsorption from contaminated water

Biopolymers are promising materials for water treatment applications due to their abundance, low cost, expandability, and chemical structure. In this work, gelatin hydrogels filled with cellulose in the form of pristine eucalyptus residues (PER) or treated eucalyptus residues (TER) were prepared for adsorption and chromium removal in contaminated water. PER is a lignocellulosic compound, with cellulose, hemicellulose, and lignin, while TER has cellulose as a major component. FT-Raman Spectroscopy and FTIR analysis confirmed the crosslink reaction with glutaraldehyde and indicated that fillers altered the gelatin molecular vibrations and formed new hydrogen bonds, impacting the hydrogels' crystalline structure. The hydrogen bond energy was altered by the cellulosic fillers' addition and resulted in higher thermal stability (~10 °C). Hydrogels presented a Fickian diffusion, where gelatin hydrogel showed the highest swelling ability (466%), and composites showed lower values with the filler content increase. The chromium adsorption capacity presented values between 12 and 13 mg/g, i.e., featuring an excellent removal capacity which is related with hydrogel crosslinked structure and fibers surface hydroxyl groups, highlighting gelatin hydrogel TER 5% with better removal capacity. The developed hydrogels were produced from biomacromolecules with low-cost and potential application in contaminated water.

Fungal chitin-glucan nanopapers with heavy metal adsorption properties for ultrafiltration of organic solvents and water

Membranes and filters are essential devices, both in the laboratory for separation of media, solvent recovery, organic solvent and water filtration purposes, and in industrial scale applications, such as the removal of industrial pollutants, e.g. heavy metal ions, from water. Due to their solvent stability, biologically sourced and renewable membrane or filter materials, such as cellulose or chitin, provide a low-cost, sustainable alternative to synthetic materials for organic solvent filtration and water treatment. Here, we investigated the potential of fungal chitin nanopapers derived from A. bisporus (common white-button mushrooms) as ultrafiltration membranes for organic solvents and aqueous solutions and hybrid chitin-cellulose microfibril papers as high permeance adsorptive filters. Fungal chitin constitutes a renewable, easily isolated, and abundant alternative to crustacean chitin. It can be fashioned into solvent stable nanopapers with pore sizes of 10-12 nm, as determined by molecular weight cut-off and rejection of gold nanoparticles, that exhibit high organic solvent permeance, making them a valuable material for organic solvent filtration applications. Addition of cellulose fibres to produce chitin-cellulose hybrid papers extended membrane functionality to water treatment applications, with considerable static and dynamic copper ion adsorption capacities and high permeances that outperformed other biologically derived membranes, while being simpler to produce, naturally porous, and not requiring crosslinking. The simple nanopaper production process coupled with the remarkable filtration properties of the papers for both organic solvent filtration and water treatment applications designates them an environmentally benign alternative to traditional membrane and filter materials.

Sources and routes of SARS-CoV-2 transmission in water systems in Africa: Are there any sustainable remedies?

Governments across the globe are currently besieged with the novel coronavirus (COVID-19) pandemic caused by SARS-CoV-2. Although some countries have been largely affected by this pandemic, others are only slightly affected. In this regard, every government is taking precautionary measures to mitigate the adverse effects of COVID-19. SARS-CoV-2 has been detected in wastewater raising an alarm for Africa due to the poor water, sanitation, and hygiene (WASH) facilities. Also, most countries in Africa do not have resilient policies governing sanitation and water management systems, which expose them to higher risk levels for the transmission of SARS-CoV-2. Therefore, this study unearthed the likely sources and routes of SARS-CoV-2 transmission in water systems (mainly wastewater) in Africa through a holistic review of published works. This provided the opportunity to propose sustainable remedial measures, which can be extrapolated to most developing countries in the world. The principal sources and routes of potential transmission of SARS-CoV-2 in water systems are hospital sewage, waste from isolation and quarantine centres, faecal-oral transmission, contaminated surface and groundwater sources, and contaminated sewage. The envisioned overwhelming impact of these sources on the transmission of SARS-CoV-2 through water systems in Africa suggests that governments need to put stringent and sustainable measures to curtail the scourge. Hence, it is proposed that governments in Africa must put measures like improved WASH facilities and public awareness campaigns, suburbanization of wastewater treatment facilities, utilizing low-cost point-of-use water treatment systems, legally backed policy interventions, and Community-Led Total Sanitation (CLTS). SARS-CoV-2 in water systems can be inactivated and destroyed by integrating ozonation, chlorination, UV irradiation, and sodium hypochlorite in low-cost point-of-use treatment systems. These proposed sustainable remedial measures can help policymakers in Africa to effectively monitor and manage the untoward impact of SARS-CoV-2 on water systems and consequently, on the health of the general public.

Bacterial nanocellulose papers with high porosity for optimized permeance and rejection of nm-sized pollutants

Access to clean potable water is increasingly becoming a struggle for whole humankind, thus water treatment to remediate wastewater and fresh water sources is an important task. Pollutants in the nanoscale, such as viruses and macromolecules, are usually removed by means of membrane filtration processes, predominantly nanofiltration or ultrafiltration. Cellulose nanopapers, prepared from renewable resources and manufactured by papermaking, have recently been demonstrated to be versatile alternatives to polymer membranes in this domain. Unfortunately, so far nanopaper filters suffer from limited permeance and thus efficiency. We here present nanopapers made from bacterial cellulose dispersed in water or different types of low surface tension organic liquids (alcohol, ketone, ether) through a simple papermaking process. Nanopapers prepared from organic liquids (BC-org) exhibited 40 times higher permeance, caused by a lower paper density hence increased porosity, compared to conventional nanopapers produced from aqueous dispersions, ultimately enhancing the efficiency of bacterial cellulose nanopaper membranes. Despite their higher porosity, BC-org nanopapers still have pore sizes of 15-20 nm similar to BC nanopapers made from aqueous dispersions, thus enabling removal of contaminants the size of viruses by a size-exclusion mechanism at high permeance.

Snowballing transmission of COVID-19 (SARS-CoV-2) through wastewater: Any sustainable preventive measures to curtail the scourge in low-income countries?

In this communication, we proposed sustainable preventive measures that may be adopted by the low-income countries to forestall the potential outbreak and transmission of COVID-19 (coronavirus disease 2019) through wastewater. Most low-income countries have poor sanitation and wastewater management policies, which create potential risks of COVID 19 spread. Hence, the proposed measures include decentralization of wastewater treatment facilities, community-wide monitoring and testing of SARS-CoV-2 in wastewater samples, improved sanitation, developing point-of-use devices for wastewater decontamination, and more focused policy interventions. Therefore, this paper adds useful insights into the monitoring and management of ongoing COVID-19 outbreak in low-income countries.

Snowballing transmission of COVID-19 (SARS-CoV-2) through wastewater: Any sustainable preventive measures to curtail the scourge in low-income countries?

In this communication, we proposed sustainable preventive measures that may be adopted by the low-income countries to forestall the potential outbreak and transmission of COVID-19 (coronavirus disease 2019) through wastewater. Most low-income countries have poor sanitation and wastewater management policies, which create potential risks of COVID 19 spread. Hence, the proposed measures include decentralization of wastewater treatment facilities, community-wide monitoring and testing of SARS-CoV-2 in wastewater samples, improved sanitation, developing point-of-use devices for wastewater decontamination, and more focused policy interventions. Therefore, this paper adds useful insights into the monitoring and management of ongoing COVID-19 outbreak in low-income countries.

Recent advances in cellulose-based membranes for their sensing applications

ABSTRACT

In recent years, sensing applications have played a very important role in various fields. As a novel natural material, cellulose-based membranes with many merits can be served as all kinds of sensors. This review summarizes the recent progress of cellulose membranes as sensors, mainly focusing on their preparation processes and sensing properties. In addition, the opportunities and challenges of cellulose membrane-based sensors are also prospected. This review provides some references for the design of cellulose membrane materials for sensing applications in the future.