Current Status of Cellulosic and Nanocellulosic Materials for Oil Spill Cleanup

Ionic-physical-chemical triple cross-linked all-biomass-based aerogel for thermal insulation applications

Aerogels, as a unique porous material, are expected to be used as insulation materials to solve the global environmental and energy crisis. Using chitosan, citric acid, pectin and phytic acid as raw materials, an all-biomass-based aerogel with high modulus was prepared by the triple strategy of ionic, physical and chemical cross-linking through directional freezing technique. Based on this three-dimensional network, the aerogel exhibited excellent compressive modulus (24.89 ± 1.76 MPa) over a wide temperature range and thermal insulation properties. In the presence of chitosan, citric acid and phytic acid, the aerogel obtained excellent fire safety (LOI value up to 31.2%) and antibacterial properties (antibacterial activity against Staphylococcus aureus and Escherichia coli reached 81.98% and 67.43%). In addition, the modified aerogel exhibited excellent hydrophobicity (hydrophobic angle of 146°) and oil-water separation properties. More importantly, the aerogel exhibited a biodegradation rate of up to 40.31% for 35 days due to its all-biomass nature. This work provides a green and sustainable strategy for the production of highly environmentally friendly thermal insulation materials with high strength, flame retardant, antibacterial and hydrophobic properties.

Superhydrophobic Non-Metallic Surfaces with Multiscale Nano/Micro-Structure: Fabrication and Application

Multiscale nano/micro-structured surfaces with superhydrophobicity are abundantly observed in nature such as lotus leaves, rose petals and butterfly wings, where microstructures typically reinforce mechanical stability, while nanostructures predominantly govern wettability. To emulate such hierarchical structures in nature, various methods have been widely applied in the past few decades to the manufacture of multiscale structures which can be applied to functionalities ranging from anti-icing and water-oil separation to self-cleaning. In this review, we highlight recent advances in nano/micro-structured superhydrophobic surfaces, with particular focus on non-metallic materials as they are widely used in daily life due to their lightweight, abrasion resistance and ease of processing properties. This review is organized into three sections. First, fabrication methods of multiscale hierarchical structures are introduced with their strengths and weaknesses. Second, four main application areas of anti-icing, water-oil separation, anti-fog and self-cleaning are overviewed by assessing how and why multiscale structures need to be incorporated to carry out their performances. Finally, future directions and challenges for nano/micro-structured surfaces are presented.

Reusable, Stable, Efficient and Multifunctional Superhydrophobic and Oleophilic Polyurethane Sponge for Oil-Water Separation Prepared Using Discarded Composite Insulator

Oil spills and chemical leakages are a serious source of pollution in oceans and rivers, and have attracted worldwide attention. Many scientists are currently engaged in the development of oil-water separation technology. In this study, the umbrella skirt of a discarded silicone rubber insulator was utilized as feedstock, and polydimethylsiloxane (PDMS) was employed to immobilize the prepared powder (FXBW) onto a polyurethane (PU) sponge skeleton. Without any modifications using chemical reagents, a novel oil-water separation material, FXBW-PU, was developed, with a water contact angle of 155.3°. The FXBW-PU sponge exhibited an absorption capacity ranging from 11.79 to 26.59 g/g for various oils and organic solvents, while maintaining an excellent selective adsorption performance, even after undergoing ten compression cycles, due to its exceptional chemical and mechanical stability. With the assistance of a vacuum pump, the FXBW-PU sponge was utilized in a continuous separation apparatus, resulting in a separation efficiency exceeding 98.6% for various oils and organic solvents. The separation efficiency of n-hexane remains as high as 99.2% even after 10 consecutive separation cycles. Notably, the FXBW-PU sponge also separated the dichloromethane-in-water emulsions, which achieved the effect of purifying water. In summary, FXBW-PU sponge has great potential in the field of cleaning up oil/organic solvent contamination due to its low preparation cost, environmental friendliness and excellent performance.

Multifunctional fully biobased aerogels for water remediation: Applications for dye and heavy metal adsorption and oil/water separation

Water ecosystem contamination from industrial pollutants is an emerging threat to both humans and native species, making it a point of global concern. In this work, fully biobased aerogels (FBAs) were developed by using low-cost cellulose filament (CF), chitosan (CS), citric acid (CA), and a simple and scalable approach, for water remediation applications. The FBAs displayed superior mechanical properties (up to ∼65 kPa m³ kg^-1 specific Young's modulus and ∼111 kJ/m³ energy absorption) due to CA acting as a covalent crosslinker in addition to the natural hydrogen bonding and electrostatic interactions between CF and CS. The addition of CS and CA increased the variety of functional groups (carboxylic acid, hydroxyl and amines) on the materials' surface, resulting in super-high dye and heavy metal adsorption capacities (619 mg/g and 206 mg/g for methylene blue and copper, respectively). Further modification of FBAs with a simple approach using methyltrimethoxysilane endowed aerogel oleophilic and hydrophobic properties. The developed FBAs showed a fast performance in water and oil/organic solvents separation with more than 96% efficiency. Besides, the FBA sorbents could be regenerated and reused for multiple cycles without any significant impact on their performance. Moreover, thanks to the presence of amine groups by addition of CS, FBAs also displayed antibacterial properties by preventing the growth of Escherichia coli on their surface. This work demonstrates the preparation of FBAs from abundant, sustainable, and inexpensive natural resources for applications in wastewater purification.

Rheological and mechanical properties of hydroxypropyl methylcellulose-based hydrogels and cryogels controlled by AOT and SDS micelles

HYPOTHESIS

The type and concentration of surfactants affect the rheological behavior of hydroxypropyl methylcellulose (HPMC) chains in hydrogels, influencing the microstructure and mechanical properties of HPMC cryogels.

EXPERIMENTS

Hydrogels and cryogels containing HPMC, AOT (bis (2-ethylhexyl) sodium sulfosuccinate or dioctyl sulfosuccinate salt sodium, two C8 chains and sulfosuccinate head group), SDS (sodium dodecyl sulfate, one C12 chain and sulfate head group), and sodium sulfate (salt, no hydrophobic chain) at different concentrations were investigated using small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), rheological measurements, and compressive tests.

FINDINGS

SDS micelles bound to the HPMC chains building "bead necklaces", increasing considerably the storage modulus G' values of the hydrogels and the compressive modulus E values of the corresponding cryogels. The dangling SDS micelles promoted multiple junction points among the HPMC chains. AOT micelles and HPMC chains did not form "bead necklaces". Although AOT increased the G' values of the hydrogels, the resulting cryogels were softer than pure HPMC cryogels. The AOT micelles are probably embedded between HPMC chains. The AOT short double chains rendered softness and low friction to the cryogel cell walls. Therefore, this work demonstrated that the structure of the surfactant tail can tune the rheological behavior of HPMC hydrogels and hence the microstructure of the resulting cryogels.

Influence of electrospinning parameters on biopolymers nanofibers, with emphasis on cellulose & chitosan

Background

Electrospinning is an effective method for producing high-quality biopolymer nanofibers, such as cellulose and chitosan. Cellulose nanofibers have excellent mechanical properties and biocompatibility, making them a promising material for tissue engineering. Chitosan nanofibers are biodegradable, biocompatible, and antimicrobial, making them ideal for biomedical applications. The electrospinning parameters, including solution concentration, power supply voltage, orifice diameter, temperature, humidity, and flow rate, play a crucial role in determining the nanofiber diameter, morphology, and mechanical properties, as well as their suitability for various applications.

Objective

This systematic review aims to synthesize and evaluate the current evidence on the influence of electrospinning parameters on the production and properties of cellulose and chitosan nanofibers.

Methods

A comprehensive search of electronic databases was conducted to identify relevant studies. The inclusion criteria were studies that investigated the effect of electrospinning parameters on cellulose and chitosan nanofibers.

Results

It was found that for cellulose, the average fiber diameter increased with increasing each of solution concentration, power supply voltage, orifice diameter, temperature, and humidity. Contrary to tip - collector distance and some optimal points in temperature, where average fiber diameter decreased. For chitosan, the change in voltage and tip to collector distance did not alter the average fiber diameter except for some readings of voltage, which behaved differently. On the other hand, the average fiber diameter increased with increasing flow rate.

Conclusion

The review highlights the importance of considering electrospinning parameters in the production of high-quality biopolymer nanofibers and provides insights into the optimization of these parameters for specific applications. This review also highlights the need for further research to better understand the underlying mechanisms of electrospinning and to optimize the process to produce biopolymer nanofibers with improved properties.

Novel Electrically Conductive Cellulose Nanocrystals with a Core-Shell Nanostructure Towards Biodegradable Electronics

Electronic waste (e-waste) is the fastest growing waste stream and its negative impact on the environment and human health is major because of the toxicity and non-biodegradability of its constituents. For their biodegradability and nontoxicity, bio-based materials have been proposed as potential material candidates in the field of electronics. Among these, cellulose nanocrystals (CNCs) have many interesting properties including biodegradability, high mechanical strength, and possibility to functionalize. In terms of electrical properties, CNCs are electrically insulated, limiting their potential in electronics. This work aims to build up a poly(o-toluidine)-like shell around the CNCs to render them conductive. For this goal, the surface of the CNCs was carbamated using 2,4-toluene diisocyanate through the para-isocyanates and the ortho-isocyanates were later hydrolyzed to amine groups using HCl-acidified dimethylsulfoxide. The resultant o-toluidine-like molecules on the CNC surface were then polymerized using ammonium persulfate to form an electrically conductive shell around each CNC. The resultant CNCs were then characterized for their chemical, morphological, and electrical properties. Fourier-transform infrared analysis of the CNCs at each stage confirmed the expected chemical changes upon carbamation, hydrolysis, and polymerization and X-ray diffraction confirmed the permanence of the native crystalline structure of the CNCs. The atomic force microscopy images showed that the obtained CNCs were on average slightly thicker than the original ones, possibly due to the growth of the poly(o-toluidine) shell around them. Finally, using the four-point method, the obtained CNCs were electrically conductive with a conductivity of 0.46 S/cm. Such novel electrically conductive CNCs should have great potential in a wide range of applications including electronics, sensing, and medicine.

Mechanically Robust and Flexible GO/PI Hybrid Aerogels as Highly Efficient Oil Absorbents

Herein, mechanically robust and flexible graphene oxide/polyimide (GO/PI) hybrid aerogels (GIAs) were fabricated by a facile method, in which the mixed suspensions of the water-soluble polyimide precursor and graphene oxide (GO) sheets were freeze-dried, which was followed by a routine thermal imidation process. The porous GIAs obtained not only exhibit excellent elasticity and extremely low density values (from 33.3 to 38.9 mg.cm^-3), but they also possess a superior compressive strength (121.7 KPa). The GIAs could support a weight of up to 31,250 times of its own weight, and such a weight-carrying capacity is much higher than that of other typical carbon-based aerogels. Having such a porous structure, and high strength and toughness properties make GIAs ideal candidates for oil spill cleanup materials. The oil/organic solvents' absorption capacity ranges from 14.6 to 85, which is higher than that of most other aerogels (sponges). With their broad temperature tolerance and acidic stability, the unique multifunctional GIAs are expected to further extend their application range into extreme environments.

Fabrication of Textile Waste Fibers Aerogels with Excellent Oil/Organic Solvent Adsorption and Thermal Properties

In recent years, the treatment of textile waste has attracted more and more attention around the world. The reuse of textile waste can contribute to the reduction of carbon emissions and the sustainable development of the economy. Herein, we proposed a facile and cost-effective approach to fabricating aerogel by using textile waste fibers as the matrix and polyvinyl alcohol (PVA) and glutaraldehyde (GA) as crosslinking agents. After being modified with methyltrimethoxysilane (MTMS) via chemical vapor deposition, both the interior and exterior of the textile waste aerogels exhibit a hydrophobic property with a water contact angle of up to 136.9° ± 2.3°. A comprehensive investigation of the structure, thermal properties, mechanical properties and oil absorption capacity of this aerogel shows its potential for building insulation and oil spill cleanup. The textile waste fibers aerogels have low density and high porosity, good thermal stability and outstanding heat insulation properties (K_avg. = 0.049–0.061 W/m·K). With a maximum oil absorption value of 26.9 ± 0.6 g/g and rapid and effective oil/water mixture separation, the aerogel exhibits competitive commercial application value.

Chitosan-Hydroxyapatite Bio-Based Composite in Film Form: Synthesis and Application in Wastewater

Water purification from toxic metals was the main objective of this work. A composite in film form was prepared from the biomaterials hydroxyapatite, chitosan and glycerol using the dissolution/recrystallization method. A nanoparticle-based film with a homogenous and smooth surface was produced. The results of total reflectance infrared spectroscopy (ATR-FTIR) and thermal gravimetric analysis (TGA/DTA) demonstrated the presence of a substantial physical force between composite components. The composite was tested for its ability to absorb Cd2+ and Zn2+ ions from aqueous solutions. Cd2+ and Zn2+ adsorption mechanisms are fit using the Langmuir model and the pseudo-second-order model. Thermodynamic parameters indicated that Cd2+ and Zn2+ ion adsorption onto the composite surface is spontaneous and preferred at neutral pH and temperatures somewhat higher than room temperature. The adsorption studies showed that the maximum adsorption capacity of the HAp/CTs bio-composite membrane for Cd2+ and Zn2+ ions was in the order of cadmium (120 mg/g) > Zinc (90 mg/g) at an equilibrium time of 20 min and a temperature of 25 °C. The results obtained on the physico-chemical properties of nanocomposite membranes and their sorption capacities offer promising potential for industrial and biological activities.

Fluorescence Labeling of Cellulose Nanocrystals—A Facile and Green Synthesis Route

Efficient chemical modification of cellulose nanocrystals (CNCs) by grafting commonly involves aprotic solvents, toxic reactants, harsh reaction conditions, or catalysts, which have negative effects on the particle character, reduced dispersibility and requires further purification, if products are intended for biomedical applications. This work, in contrast, presents a robust, facile, and green synthesis protocol for the grafting of an amino-reactive fluorophore like fluorescein isothiocyanate (FITC) on aqueous CNCs, combining and modifying existent approaches in a two-step procedure. Comparably high grafting yields were achieved, which were confirmed by thermogravimetry, FTIR, and photometry. The dispersive properties were confirmed by DLS, AF4-MALS, and TEM studies. The presented route is highly suitable for the introduction of silane-bound organic groups and offers a versatile platform for further modification routes of cellulose-based substrates.

Removal of Petroleum Hydrocarbons from Brackish Water by Natural and Modified Sorbents

Crude oil and petroleum products made from it are increasingly being extracted and consumed worldwide as an important energy source. During necessary transportation, e.g., by tanker, an oil spill might occur, which leads to water pollution by oil. One of the methods of cleaning up oil spills is to use sorbents, preferably made from natural materials. This study evaluates the remediation efficiency of brackish water polluted with crude oil, marine diesel oil (MDO) and lubricating oil. The experiment was performed with three different sorbents (straw, straw modified with methoxytrimethylsilanes (MTMS) and wood chip shavings) and without them. The evaporation loss and the dissolved and sorbed fractions of oil were measured by gas chromatography (GC) to evaluate remediation efficiency. Hydrophobization made the natural sorbents buoyant for the duration of the experiment, with only a slight increase in the maximum sorption capacity. The sorbents increased the evaporation of the oils and also of the water, reduced the proportion of the oil dissolved in water and retained the sorbed proportion for the lubricating oil and partly for the MDO, to such an extent that it could not be extracted entirely even after a 60-min extraction time.

Eco-Friendly and Complete Recycling of Waste Bamboo-Based Disposable Paper Cups for Value-Added Transparent Cellulose-Based Films and Paper Plastic Composites

Disposable paper cups are widely used in daily life and most of them are landfilled or incinerated after use, resulting in a serious ecological hazard and significant waste of resources due to the usage of thin polyethylene (PE) as their inner coating. Hence, converting these common solid domestic wastes into high-value added materials is attractive and meaningful. In this study, transparent cellulose-based films were achieved from old bamboo-based disposable paper cups after pretreatment through using the room ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as solvent. The cellulose-based film with a dense texture demonstrated a relatively nice mechanical and UV-shielding performances, and its tensile strength was as high as 48 MPa, much higher than that of commercial polyethylene (PE, 12 MPa) film. Thus, the resultant cellulose-based film showed a great potential in the packaging field. Besides, the flexible paper plastic composites (PPC) were also fabricated from the rest thin PE coating with the stuck fibers, and it was found that PPC showed excellent mechanical property and hydrophobicity. Consequently, a feasible and eco-friendly process of recycling and reusing waste disposable paper cups was developed to achieve a complete utilization and valorization of waste disposable paper cups.

Sustainable Cross-Linkers for the Synthesis of Cellulose-Based Aerogels: Research and Application

Cellulose aerogels with polyester resin as cross-linkers have attracted much attention. This study describes the route to produce a fully bio-based aerogel with high added value from waste paper and starch, cellulose acetate and starch–cellulose acetate mixture as cross-linkers for oil adsorption, instead of the environmentally harmful polyester resin. The manufacturing process is simple, sustainable and cost-efficient, without releasing harmful by-products into the environment. The effects of different cross-linkers on the oil adsorption, dynamic oil retention, reusability and morphology of the aerogels were studied in detail. Experimental results show that these environmentally friendly recycled aerogels have a very low density, i.e., —0.0110–0.0209 g cm−3, and highly porous structures, with a porosity of 96.74–99.18%. The synthesized hydrophobic aerogels showed contact angles of ∼124–129°. The compression moduli are lower than that of an aerogel with polyester as a cross-linker, but the compression modulus of the mixture of starch and cellulose acetate especially shows a higher value than expected. The sorption capacity of the aerogels with bio-based cross-linkers was significantly increased compared to the aerogels with polyester; it is now up to 56 times their own weight. The aerogels also have good oil-retention properties.

Cellulose-Based Materials for Water Remediation: Adsorption, Catalysis, and Antifouling

Cellulose-based materials have been advanced technologies that used in water remediation. They exhibit several advantages being the most abundant biopolymer in nature, high biocompatibility, and contain several functional groups. Cellulose can be prepared in several derivatives including nanomaterials such as cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidized cellulose nanofibrils (TOCNF). The presence of functional groups such as carboxylic and hydroxyls groups can be modified or grafted with organic moieties offering extra functional groups customizing for specific applications. These functional groups ensure the capability of cellulose biopolymers to be modified with nanoparticles such as metal-organic frameworks (MOFs), graphene oxide (GO), silver (Ag) nanoparticles, and zinc oxide (ZnO) nanoparticles. Thus, they can be applied for water remediation via removing water pollutants including heavy metal ions, organic dyes, drugs, and microbial species. Cellulose-based materials can be also used for removing microorganisms being active as membranes or antibacterial agents. They can proceed into various forms such as membranes, sheets, papers, foams, aerogels, and filters. This review summarized the applications of cellulose-based materials for water remediation via methods such as adsorption, catalysis, and antifouling. The high performance of cellulose-based materials as well as their simple processing methods ensure the high potential for water remediation.