Enhanced properties of tea residue cellulose hydrogels by addition of graphene oxide

Development and characterization of pH responsive sodium alginate hydrogel containing metal-phenolic network for anthocyanin delivery

Favorable hydrogels can be used as a material to deliver bioactive molecules and improve the stability of bioactive substances, while their safety needs to be improved. In this study, protocatechuic acid (PCA) and Fe3+ were rapidly self-assembled to form a metal-phenolic network under different pH conditions, and then sodium alginate (SA) was added to prepare the SA/PCA/Fe hydrogel without adding other chemical reagents. The structural characteristic of SA/PCA/Fe hydrogel was characterized by infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The results showed that the structures of SA/PCA/Fe hydrogels prepared at different pH values were significantly different. The texture analysis, water-holding measurement and rheological analysis indicated that the SA/PCA/Fe hydrogel showed higher gel strength, water holding capacity and storage modulus. Thermogravimetric analysis illuminated that the SA/PCA/Fe hydrogel enhanced the thermal stability of free anthocyanins through encapsulating anthocyanins. Moreover, in vitro simulated digestion experiment revealed that SA/PCA/Fe hydrogel could control the release of anthocyanins in the simulated gastrointestinal tract. To sum up, this present study might provide a safer and feasible way for the delivery of bioactive substances.

Development of carboxymethyl cellulose-graphene oxide biobased composite for the removal of methylene blue cationic dye model contaminate from wastewater

Utilizing Glutaraldehyde crosslinked sodium carboxymethyl cellulose (CMC-GA) hydrogel and its nanographene oxide composite (CMC-GA-GOx), an effective carboxymethyl cellulose-graphene oxide biobased composites adsorbent was developed for the adsorption removal of methylene blue (MB) cationic dye contaminate from industrial wastewater. The CMC-GA-GOx composites developed were characterized using FTIR, RAMAN, TGA, SEM, and EDX analysis instruments. Through batch experiments, several variables affecting the removal of MB dye, including the biocomposites GO:CMC composition, adsorption time, pH and temperature, initial MB concentration, adsorbent dosage, and NaCl concentration, were investigated under different conditions. The maximum dye removal percentages ranged between 93 and 98%. They were obtained using biocomposites CMC-GA-GO102 with 20% GO weight percent, adsorption time 25 min, adsorption temperature 25 °C, MB concentrations 10-30 ppm, adsorption pH 7.0, and 0.2 g adsorbent dose. The experimental data of the adsorption process suit the Langmuir isotherm more closely with a maximal monolayer adsorption capacity of 76.92 mg/g. The adsorption process followed the kinetic model of pseudo-second order. The removal of MB was exothermic and spontaneous from a thermodynamic standpoint. In addition, thermodynamic results demonstrated that adsorption operates most effectively at low temperatures. Finally, the reusability of the developed CMC-GA-GO102 has been proved through 10 successive cycles where only 14% of the MB dye removal percentage was lost. These results suggest that the developed CMC-GA-GO102 composite may be an inexpensive and reusable adsorbent for removing organic cationic dyes from industrial wastewater.

Locust bean gum provides excellent mechanical and release attributes to soy protein-based natural hydrogels

The current study concentrated on designing soy protein (SP)-based natural hydrogels in the presence of locust bean gum (LBG). For this, the gums were recovered from the kernel of the relevant plant and incorporated into SP gel models. Three more hydrogels were fabricated using commercial carbohydrates (gum Arabic (GA), maltodextrin (MD), and pectin (PC)) to decipher exactly the ability of LBG in these models. The chemical and morphological structures of the samples were elaborated by FTIR and SEM analyses. The coexistence of protein and carbohydrates led to an enhancement in functional (water holding capacity (WHC), swelling ratio, protein leachability, volumetric gel index (VGI)) and mechanical (textural and rheological behavior) features of natural gels compared to SP alone (control) but the quality of hydrogels was impressed by the carbohydrate type. Hydrogels designed with LBG came to the fore in terms of these attributes. Additionally, these gel models created awareness for phenolic delivery.

Recoverable cellulose composite adsorbents for anionic/cationic dyes removal

GO/HEC/PGDE/Fe₃O₄ materials were successfully fabricated using environmentally-friendly hydroxyethyl cellulose (HEC), poly(ethylene glycol) diglycidyl ether (PGDE), graphene oxide (GO) and magnetic Fe₃O₄. Systematic investigations were completed to explore the influences of GO content in GO/HEC/PGDE/Fe₃O₄ and adsorption conditions on the adsorptions of cationic dyes (methylene blue (MB), crystal violet (CV)) and anionic dye acid blue 25 (AB-25). The increase of GO content can remarkably improve the adsorption capacity of GO/HEC/PGDE/Fe₃O₄ for the dyes. The three kinetic, four isothermic and three thermodynamic models were investigated to reveal the adsorption behaviors of the dyes. The formation of HEC/PGDE/Fe₃O₄ and adsorption mechanisms of the dyes by GO/HEC/PGDE/Fe₃O₄ were suggested. The GO/HEC/PGDE/Fe₃O₄ endowed with easy-fabrication, eco-friendly feature, efficient adsorption capacity of anionic/cationic dyes, convenient separation and reusability has potential applications in wastewater purification industry.

Hypoglycemic Activity of Self-Assembled Gellan Gum-Soybean Isolate Composite Hydrogel-Embedded Active Substance-Saponin

In order to avoid hemolysis caused by direct dietary of kidney tea saponin, complex gels based on gellan gum (GG) and soybean isolate protein (SPI) loaded with saponin were created in the present study by using a self-assembly technique. Studies were conducted on the rheological characteristics, encapsulation effectiveness, molecular structure, microstructure, and hypoglycemic activity of GG/SPI-saponin gels. Increasing the concentration of SPI helped to enhance the strength and energy storage modulus (G') of the gels, and the incorporation of high acylated saponin allowed the whole gel to undergo sol-gel interconversion. The encapsulation efficiency showed that GG/SPI-saponin was 84.52 ± 0.78% for saponin. Microstructural analysis results suggested that GG and SPI were bound by hydrogen bonds. The in vitro digestion results also indicated that saponin could be well retained in the stomach and subsequently released slowly in the intestine. In addition, the in vitro hypoglycemic activity results showed that the IC₅₀ of encapsulated saponin against α-glucosidase and α-amylase were at 2.4790 mg/mL and 1.4317 mg/mL, respectively, and may be used to replace acarbose for hypoglycemia.

Prospecting cellulose fibre-reinforced composite membranes for sustainable remediation and mitigation of emerging contaminants

Many environmental pollutants caused by uncontrolled urbanization and rapid industrial growth have provoked serious concerns worldwide. These pollutants, including toxic metals, dyes, pharmaceuticals, pesticides, volatile organic compounds, and petroleum hydrocarbons, unenviably compromise the water quality and manifest a severe menace to aquatic entities and human beings. Therefore, it is of utmost importance to acquaint bio-nanocomposites with the capability to remove and decontaminate this extensive range of emerging pollutants. Recently, considerable emphasis has been devoted to developing low-cost novel materials obtained from natural resources accompanied by minimal toxicity to the environment. One such component is cellulose, naturally the most abundant organic polymer found in nature. Given bio-renewable sources, natural abundance, and impressive nanofibril arrangement, cellulose-reinforced composites are widely engineered and utilized for multiple applications, such as wastewater decontamination, energy storage devices, drug delivery systems, paper and pulp industries, construction industries, and adhesives, etc. Environmental remediation prospective is among the fascinating application of these cellulose-reinforced composites. This review discusses the structural attributes of cellulose, types of cellulose fibrils-based nano-biocomposites, preparatory techniques, and the potential of cellulose-based composites to remediate a diverse array of organic and inorganic pollutants in wastewater.

Surface Functionalization of Graphene Oxide with Hyperbranched Polyamide-Amine and Microcrystalline Cellulose for Efficient Adsorption of Heavy Metal Ions

Graphene oxide (GO)-based adsorbents have received attention in the removal of heavy metal ions in wastewater due to its large specific surface area and oxygen-containing functional groups, which can enhance the interaction between GO and heavy metal ions. Many researchers are seeking economical and effective strategies to further improve the adsorption capacity of GO. In this study, hyperbranched polymers and cellulose were used to surface functionalize GO for the efficient adsorption of heavy metal ions. First, hyperbranched polyamide-amine (HPAMAM) functionalized GO was fabricated by the formation of an amide bond between the carboxyl group of GO and the amino group of HPAMAM, increasing the active groups on the GO surface and enhancing the affinity with heavy metal ions. Then, dialdehyde cellulose (DAC) obtained through the oxidation of microcrystalline cellulose was grafted onto GO/HPAMAM by forming a Schiff-based structure between the amino group of HPAMAM and aldehyde group of DAC. Interestingly, DAC formed micro/nano bumps on GO, which was beneficial to increase the hydroxyl number and contact area with heavy metal ions. The Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) results confirmed the successful synthesis of GO/HPAMAM/DAC. The obtained GO/HPAMAM/DAC adsorbent exhibited strong adsorption capacity and good cycle stability for heavy metal ions. The maximum adsorption capacities of Pb(II), Cd(II), and Cu(II) were 680.3, 418.4, and 280.1 mg/g at 298 K, which were better than those of most adsorbents reported. A pseudo-second-order kinetic model could well-describe the Pb(II), Cd(II), and Cu(II) adsorption onto GO/HPAMAM/DAC, and the equilibrium data fitted well with the Langmuir isotherm model. The adsorption of Pb(II), Cd(II), and Cu(II) was mainly attributed to the chelation or complexation of nitrogen- and oxygen-containing groups on the GO/HAPAMAM/DAC adsorbent. This study may provide a novel strategy for improving the adsorption performance of GO with hyperbranched polymers and cellulose.

Designing cellulose hydrogels from non-woody biomass

Hydrogels are an attractive system for a myriad of applications. While most hydrogels are usually formed from synthetic materials, lignocellulosic biomass appears as a sustainable alternative for hydrogel development. The valorization of biomass, especially the non-woody biomass to meet the growing demand of the substitution of synthetics and to leverage its benefits for cellulose hydrogel fabrication is attractive. This review aims to present an overview of advances in hydrogel development from non-woody biomass, especially using native cellulose. The review will cover the overall process from cellulose depolymerization, dissolution to crosslinking reaction and the related mechanisms where known. Hydrogel design is heavily affected by the cellulose solubility, crosslinking method and the related processing conditions apart from biomass type and cellulose purity. Hence, the important parameters for rational designs of hydrogels with desired properties, particularly porosity, transparency and swelling characteristics will be discussed. Current challenges and future perspectives will also be highlighted.

Nitrogen and sulfur codoped graphene aerogels as absorbents and visible light-active photocatalysts for environmental remediation applications

Graphene aerogels (GAs) are increasingly being recognized as high performance multifunctional materials to tackle our current and emerging environmental concerns. In order to extend the application potential of GAs, herein we have successfully synthesized nitrogen (N) and sulfur (S) codoped GAs (NSGAs) via a simple, scalable, and inexpensive approach. Owing to their large specific surface area (up to 132 m² g^-1), profound porosity, superior mechanical properties, and coexistence of N and S atoms with tunable atomic content and bonding configurations, the as-prepared NSGAs demonstrated exceptional absorption capacity toward a broad spectrum of oils and organic solvents, with an average absorption rate many folds higher than conventional absorbents. Further, the NSGAs exhibited excellent photocatalytic activity for the decomposition of recalcitrant organic compounds under visible light illumination due to pronounced synergistic coupling effect between the heteroatoms. Specifically, after 5 h of exposure to visible light, a degradation efficiency of over 99% was observed and more than 84% of the total organic carbon was eliminated. Radical trapping experiments revealed that superoxide anion radicals are the predominant oxygen reactive species driving the photocatalytic reactions. More importantly, the mineralization byproducts did not pose any significant antibacterial activity, illustrating the environmentally benign nature of these macroscale photocatalysts.

Biopolymer-Based Composite Materials Prepared Using Ionic Liquids

Biopolymer-based composite materials have many potential applications in biomedical, pharmaceutical, environmental, biocatalytic, and bioelectronic fields, owing to their inherent biocompatibility and biodegradability. When used as solvents, ionic liquids can be used to fabricate biopolymers such as polysaccharides and proteins into various forms, including molded shapes, films, fibers, and beads. This article summarizes the processes for preparing biopolymer-based composite materials using ionic liquids. The processes include biopolymer dissolution using ionic liquids, regeneration of the biopolymer by an anti-solvent, formation of shapes, and drying of the regenerated biopolymer. In particular, the preparation and applications of biopolymer blend-based composite materials containing two or more biopolymers are addressed.