Recovery of Model Pharmaceutical Compounds from Water and Organic Solutions with Alginate-Based Composite Membranes

Elimination of non-specific adsorption in the molecularly imprinted membrane: application for tetracycline detection

A vital challenge in using imprinted membranes for selective sensing is their non-specific adsorption (NSA). In this study, a novel, rapid, and green approach of NSA-free molecularly imprinted membrane (MIM) preparation was proposed. Sodium alginate was employed as a functional polymer (to interact with the template) and as a membrane matrix, then cross-linked with calcium before template removal to block the unreacted groups, followed by exposure to phosphate to chelate any remaining sites. Unlike the non-imprinted membrane (NIM), which is prepared similarly to MIM and lacks the template cavities, the MIM demonstrated exceptional imprinting factor (IF) (Q(NIM) ≈ 0 mg/g) compared to the initial IF of around 4 before NSA suppress, and a selectivity factor over 10 times greater than that of existing MIMs in the literature. The NSA-free MIM was used as a ready-to-use sensor for spectro-fluorescence and smartphone-based fluorescence detection of tetracycline (TC), achieving detection limits of 0.005 mg/L and 0.015 mg/L, respectively, which were below the maximal acceptable concentrations of TC in real samples. The detection of TC in milk and honey samples using the NSA-free MIM showed significant recoveries (86-101%) compared to those found by MIM before NSA supress (114-122%). The proposed methodology serves as an inspiration for extending NSA removal strategies to other MIMs based on various anionic polymers, including carboxylate, sulfonate, phosphonate, and phenolate anionic groups.

Tailoring amino-functionalized n-alkyl methacrylate ester-based bio-hybrids for adsorption of methyl orange dye: Controllable macromolecular architecture via polysaccharide-integrated ternary copolymerization

Controllable macromolecular architecture formation via polysaccharide integrated ternary copolymerization was explored in the design of amino-functionalized n-alkyl methacrylate ester-based biohybrids. Ternary poly(dimethylaminoethyl methacrylate-co-glycidyl methacrylate-co-hydroxypropyl methacrylate)/sodium-alginate, PDGH/ALG, hybrids were designed using anionic polysaccharide through in-situ radical polymerization. An insight into the effect of ALG on physicochemical structure of ternary hybrids, particularly the interactions between polymeric chains, was created. In addition to incorporation of ALG, the effect of polymerization under cryocondition on mechanical stiffness of hybrids was investigated. Adding 0.5 % ALG to ternary PDGH matrix resulted in a 4.2-fold increase in compressive modulus. Swelling of hybrid hydrogels prepared at 1 °C decreased by 5 times, while a 3.4-fold decrease was observed in hybrid cryogels formed at -18 °C. ALG-rich hybrids showed "salting-in" behavior with increasing salt concentration in NaCl, KCl and MgCl2 solutions, while hybrids with low ALG-content exhibited "salting-out" behavior. The hybrid gels were applied to adsorption of anionic dye methyl orange (MO) from simulated dye wastewater. The adsorption was found to follow Freundlich mechanism and a pseudo-second-order kinetic model. ALG-integrated hybrid gels showed a high desorption efficiency and a longer lifespan during the regeneration process, thus showing potential to be used for anionic dye removal from textile wastewater in industry.

Membranes Based on Cellulose and Copolymers of Acrylonitrile Prepared from Joint Solutions

Cellulose and copolymers of acrylonitrile (PAN) are characterized by their chemical resistance to several conventional solvents. Therefore, these polymers are often used to obtain membranes for the recovery of such solvents. In this work, for the first time, composite membranes formed from highly concentrated mixed solutions based on cellulose and PAN are considered (the total content of polymers is 18 wt.%). For mixed solutions, the morphology and rheological behavior were evaluated. It is shown that the resulting solutions are two-phase, and their morphology depends on the components' ratio and the system's history. The non-monotonous change in the viscosity with the PAN content indicates a specific interaction of cellulose and PAN in N-methylmorpholine-N-oxide solutions. The rheological behavior of mixed solutions allows for their processing in conditions identical to those of cellulose solutions. The introduction of PAN into the cellulose matrix promotes a decrease in the structural order in the system, affecting the membranes' transport properties. For composite membranes, it was found that with an increase in the content of the PAN phase, the retention of Remazol and Orange decreases, while the observed values are several times higher than those for cellulose membranes. The permeability of ethanol increases with increasing terpolymer content.

State of Innovation in Alginate-Based Materials

This review article presents past and current alginate-based materials in each application, showing the widest range of alginate's usage and development in the past and in recent years. The first segment emphasizes the unique characteristics of alginates and their origin. The second segment sets alginates according to their application based on their features and limitations. Alginate is a polysaccharide and generally occurs as water-soluble sodium alginate. It constitutes hydrophilic and anionic polysaccharides originally extracted from natural brown algae and bacteria. Due to its promising properties, such as gelling, moisture retention, and film-forming, it can be used in environmental protection, cosmetics, medicine, tissue engineering, and the food industry. The comparison of publications with alginate-based products in the field of environmental protection, medicine, food, and cosmetics in scientific articles showed that the greatest number was assigned to the environmental field (30,767) and medicine (24,279), whereas fewer publications were available in cosmetic (5692) and food industries (24,334). Data are provided from the Google Scholar database (including abstract, title, and keywords), accessed in May 2023. In this review, various materials based on alginate are described, showing detailed information on modified composites and their possible usage. Alginate's application in water remediation and its significant value are highlighted. In this study, existing knowledge is compared, and this paper concludes with its future prospects.

Eco-Friendly OSN Membranes Based on Alginate Salts with Variable Nanofiltration Properties

In this work, membranes for organic solvents nanofiltration (OSN) based on a natural polymer, sodium alginate, were fabricated. They are chemically stable in organic solvents, including aprotic polar solvents. The unique advantage of these membranes is the absence of toxic reagents and solvents during their production. This ensures the safety and environmental friendliness of the production process. It has been shown that an operation as simple as changing the cation in alginate (Cu²⁺, Fe³⁺, Cr³⁺, Al³⁺, Zn²⁺, Ca²⁺) makes it possible to control the transport and separating properties of membranes, depending on the organic solvent being separated. Therefore, to isolate RemazolBrilliant Blue with MM = 626 g·mol^-1 from ethanol, membranes based on iron alginate with a rejection R = 97% and a permeability of 1.5 kg·m^-2·h^-1·bar^-1 are the most efficient. For isolation of the same solute from DMF and MP, membranes based on calcium alginate with an R of about 90% and a permeability of 0.1-0.2 kg·m^-2·h^-1·bar^-1 are the most efficient. The resulting membranes based on natural biodegradable sodium alginate are competitive compared to membranes based on synthetic polymers.

Alginate Ag for Composite Hollow Fiber Membrane: Formation and Ethylene/Ethane Gas Mixture Separation

Membranes based on natural polymers, in particular alginate, are of great interest for various separation tasks. In particular, the possibility of introducing silver ions during the crosslinking of sodium alginate makes it possible to obtain a membrane with an active olefin transporter. In this work, the creation of a hollow fiber composite membrane with a selective layer of silver alginate is proposed for the first time. The approach to obtaining silver alginate is presented in detail, and its sorption and transport properties are also studied. It is worth noting the increased selectivity of the material for the ethylene/ethane mixture (more than 100). A technique for obtaining a hollow fiber membrane from silver alginate has been developed, and its separating characteristics have been determined. It is shown that in thin layers, silver alginate retains high values of selectivity for the ethylene/ethane gas pair. The obtained gas transport properties demonstrate the high potential of using membranes based on silver alginate for the separation of an olefin/paraffin mixture.

Fabrication, Property and Application of Calcium Alginate Fiber: A Review

As a natural linear polysaccharide, alginate can be gelled into calcium alginate fiber and exploited for functional material applications. Owing to its high hygroscopicity, biocompatibility, nontoxicity and non-flammability, calcium alginate fiber has found a variety of potential applications. This article gives a comprehensive overview of research on calcium alginate fiber, starting from the fabrication technique of wet spinning and microfluidic spinning, followed by a detailed description of the moisture absorption ability, biocompatibility and intrinsic fire-resistant performance of calcium alginate fiber, and briefly introduces its corresponding applications in biomaterials, fire-retardant and other advanced materials that have been extensively studied over the past decade. This review assists in better design and preparation of the alginate bio-based fiber and puts forward new perspectives for further study on alginate fiber, which can benefit the future development of the booming eco-friendly marine biomass polysaccharide fiber.

Enhancing the Dye-Rejection Efficiencies and Stability of Graphene Oxide-Based Nanofiltration Membranes via Divalent Cation Intercalation and Mild Reduction

Laminar graphene oxide (GO) membranes have demonstrated great potential as next-generation water-treatment membranes because of their outstanding performance and physicochemical properties. However, solute rejection and stability deterioration in aqueous solutions, which are caused by enlarged nanochannels due to hydration and swelling, are regarded as serious issues in the use of GO membranes. In this study, we attempt to use the crosslinking of divalent cations to improve resistance against swelling in partially reduced GO membranes. The partially reduced GO membranes intercalated by divalent cations (i.e., Mg2+) exhibited improved dye-rejection efficiencies of up to 98.40%, 98.88%, and 86.41% for methyl orange, methylene blue, and rhodamine B, respectively. In addition, it was confirmed that divalent cation crosslinking and partial reduction could strengthen mechanical stability during testing under harsh aqueous conditions (i.e., strong sonication).