Pervaporative dehydration characteristics of an ethanol/water azeotrope through various chitosan membranes

Green Fabrication of Sustainable Porous Chitosan/Kaolin Composite Membranes Using Polyethylene Glycol as a Porogen: Membrane Morphology and Properties

One of the major challenges in membrane manufacturing today is to reduce the environmental footprint by promoting biobased raw materials and limiting the use of toxic solvents. In this context, environmentally friendly chitosan/kaolin composite membranes, prepared using phase separation in water induced by a pH gradient, have been developed. Polyethylene glycol (PEG) with a molar mass ranging from 400 to 10,000 g·mol^-1 was used as a pore forming agent. The addition of PEG to the dope solution strongly modified the morphology and properties of the formed membranes. These results indicated that PEG migration induced the formation of a network of channels promoting the penetration of the non-solvent during the phase separation process, resulting in an increase in porosity and the formation of a finger-like structure surmounted by a denser structure of interconnected pores of 50-70 nm in diameter. The hydrophilicity of the membrane surface increased likely related to PEG trapping in the composite matrix. Both phenomena were more marked as the PEG polymer chain was longer, resulting in a threefold improvement in filtration properties.

Performance Enhancement of Kaolin/Chitosan Composite-Based Membranes by Cross-Linking with Sodium Tripolyphosphate: Preparation and Characterization

A new family of environmentally friendly and low-cost membranes based on readily available mineral and polymeric materials has been developed from cast suspensions of kaolin and chitosan using aqueous phase separation and polyethylene glycol as a pore-forming agent. The as-fabricated membranes were further cross-linked with sodium tripolyphosphate (STPP) in order to strengthen the properties of the obtained samples. The functional groups determined by FTIR and EDX confirmed that the reaction occurred. A detailed study of the effects of cross-linking time on the physicochemical, surface and permeation properties showed that a 30-minute reaction enabled the composite membrane to be stable in acidic media (up to pH 2) and increased the mechanical strength twofold compared to the non-cross-linked membrane. A similar morphology to that generally observed in polymeric membranes was obtained, with a sponge-like surface overlaying a finger-like through structure. The top layer and cross-section thicknesses of the membranes increased during STPP post-treatment, while the pore size decreased from 160 to 15 nm. At the same time, the molecular weight cut-off and permeance decreased due to the increase in cross-linking density. These results observed in a series of kaolin/chitosan composite membranes showed that STPP reaction can provide control over the separation capability range, from microfiltration to ultrafiltration.

Mechanochemical Transformations of Biomass into Functional Materials

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Preparation of water-soluble dialdehyde cellulose enhanced chitosan coating and its application on the preservation of mandarin fruit

Biopolymers, e.g., polysaccharides and protein, have been employed as edible coatings for the preservation of fruits for many years and are the promising candidates for resolving the problems caused by the extensive using of synthesized polymers in recent years. Chitosan, a kind of polysaccharide with excellent antibacterial and coatings forming properties, has attracted a lot of research interests in being applied as an edible coating for the preservation of postharvest fruits. However, the applying of chitosan is restricted by its poor stability. In this study, we introduce the water-soluble dialdehyde cellulose (DAC) as the crosslinking agent for chitosan to enhance its stability. Fourier transform-infrared spectroscopy is applied to prove the happening of crosslinking and the detection of swelling ratio in water and mechanical properties of DAC-crosslinked chitosan (DAC/CS) confirms the enhanced stability. Furthermore, scanning electron microscope, thermogravimetric analysis, water contact angle, mechanical and gas barrier properties are performed to characterize DAC/CS films with different DAC contents. Finally, DAC/CS is employed as a coating agent to study the effect on the storage of mandarin fruit at room temperature. Chitosan, with enhanced stability by biopolymer, would be a promising candidate applied as a green edible coating in the preservation of fruits.

High-performance pervaporation chitosan-based membranes: new insights and perspectives

Today, the need of replacing synthetic polymers in the membrane preparation for diverse pervaporation (PV) applications has been recognized collectively and scientifically. Chitosan (CS), a bio-polymer, has been studied and proposed to achieve this goal especially in specific azeotropic water-organic, organic-water, and organic-organic separations, as well as in assisting specific processes (e.g. seawater desalination and chemical reactions). Different concepts of CS-based membranes have been developed, which include material blending and composite and mixed matrix membranes which have been tested for different separations. Hereby, the goal of this review is to provide a critical overview of the ongoing CS-based membrane developments, paying a special attention to the most relevant findings and results in the field. Furthermore, future trends of CS-based membranes in PV technology are presented, as well as concluding remarks and suggested strategies for the new scientist in the field.

Natural Polysaccharide Nanomaterials: An Overview of Their Immunological Properties

Natural occurring polymers, or biopolymers, represent a huge part of our planet biomass. They are formed by long chains of monomers of the same type or a combination of different ones. Polysaccharides are biopolymers characterized by complex secondary structures performing several roles in plants, animals, and microorganisms. Because of their versatility and biodegradability, some of them are extensively used for packaging, food, pharmaceutical, and biomedical industries as sustainable and renewable materials. In the recent years, their manipulation at the nanometric scale enormously increased the range of potential applications, boosting an interdisciplinary research attempt to exploit all the potential advantages of nanostructured polysaccharides. Biomedical investigation mainly focused on nano-objects aimed at drug delivery, tissue repair, and vaccine adjuvants. The achievement of all these applications requires the deep knowledge of polysaccharide nanomaterials' interactions with the immune system, which orchestrates the biological response to any foreign substance entering the body. In the present manuscript we focused on natural polysaccharides of high commercial importance, namely, starch, cellulose, chitin, and its deacetylated form chitosan, as well as the seaweed-derived carrageenan and alginate. We reviewed the available information on their biocompatibility, highlighting the importance of their physicochemical feature at the nanoscale for the modulation of the immune system.

Recent advances in cellulose and chitosan based membranes for water purification: A concise review

Recently membrane technology has emerged as a new promising and pervasive technology due to its innate advantages over traditional technologies such as adsorption, distillation and extraction. In this article, some of the recent advances in developing polymeric composite membrane materials for water purification from natural polysaccharide based polymers namely cellulose derivatives and chitosan are concisely reviewed. The impact of human social, demographic and industrial evolution along with expansion through environment has significantly affected the quality of water by pollution with large quantities of pesticides, minerals, drugs or other residues. At the forefront of decontamination and purification techniques, we found the membrane materials from polymers as a potential alternative. In an attempt to reduce the number of technical polymers widely used in the preparation of membranes, many researchers have reported new solutions for desalination or retention of organic yeasts, based on bio renewable polymers like cellulose derivatives and chitosan. These realizations are presented and discussed in terms of the most important parameters of membrane separation especially water flux and retention in this article.

Investigation into glutaraldehyde crosslinked chitosan/cardo-poly-etherketone composite membrane for pervaporation separation of methanol and dimethyl carbonate mixtures

Methanol/dimethyl carbonate mixtures were separated using GA–STA–CS/PEK-C membrane, which was prepared using glutaraldehyde (GA) crosslinked silicatungtic acid hydrate (STA)/chitosan (CS) as active layer and cardo-polyetherketone (PEK-C) as substrate.