Radiation synthesis and characterization of super-absorbing hydrogel from natural polymers and vinyl monomer

Improving Water Retention in Sandy Soils with High-Performance Superabsorbents Hydrogel Polymer

Improving the water retention capability of drained and sandy soils is vital for nurturing high-quality soil. This protective measure ensures the conservation of essential nutrients, such as fertilizers and organic matter; maintains soil quality; and prevents erosion. Superabsorbent hydrogels (SAHs) have emerged as promising solutions to boost water retention in sandy soils, typically characterized by a poor water-holding capacity. However, there is a noticeable gap in the existing literature regarding their potential to simultaneously achieve elevated swelling ratio (SR) and water retention ratio (WRR) levels. This study presents innovative SAH systems with the highest reported SR value yet, exceeding 10000 wt %, and remarkable WRR capability explicitly designed for agricultural use. These novel SAHs were synthesized using the chemical cross-linking polymerization method from polyacrylamide (PAM) polymer, employing various PAM ratios through a one-pot hydrothermal vessel method along with diverse drying techniques. The prepared hydrogels were characterized using various techniques, such as FTIR and DSC; unraveling insights into their structural properties; and the kinetics of the swelling process. Notably, these synthesized hydrogels exhibit robustness, maintaining structural integrity even under extreme conditions such as high temperatures or pressures. Our findings suggest immense potential for these hydrogels as soil enhancers in agriculture, offering a sustainable solution to bolster soil quality and nutrient preservation.

Rice straw derived cellulose-based hydrogels synthesis and applications as water reservoir system

This study synthesized new cellulose-based hydrogels, namely cellulose and cellulose/poly acrylic acid, using cellulose extracted from rice straw via alkaline and acidic pulping processes. The research demonstrated alkaline treatment with sodium hydroxide to be more effective for cellulose extraction compared to acidic treatment. Hydrogel synthesis used graft polymerization and chemical crosslinking with potassium persulfate as initiator and epichlorohydrin as a crosslinker. Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TG), and scanning electron microscopy (SEM) characterized the prepared hydrogels. Important factors determining hydrogel competence are swelling ratio and water retention rate. The cellulose hydrogel exhibited the highest swelling ratio in tap water (9811%) with 76.25 wt% water retention and in artificial hard water (3121.43%) with 64.58 wt% retention after 4 days outdoors at 298 K. Finally, hydrogels were investigated extensively for agricultural applications. Fenugreek seeds germinated and grew well (67% germination after 7 days) in normal soil mixed with 10% cellulose hydrogel. Biodegradability testing exhibited 6% degradation after 40 days and 10% after 120 days in an open-air lab at room temperature and 60% humidity.

Efficient removal of copper and silver ions in electroplating wastewater by magnetic-MOF-based hydrogel and a reuse case for photocatalytic application

Direct discharge of electroplating wastewater containing hazardous metal ions such as Cu2+ and Ag + results in environmental pollution. In this study, we rationally prepare a magnetic composite hydrogel consisted of Fe3O4, UiO-66-NH2, chitosan (CTS) and polyethyleneimine (PEI), namely Fe3O4@UiO-66-NH2/CTS-PEI. Thanks to the strong attraction between the amino group and metal cations, the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel shows the maximum adsorption capacities of 321.67 mg g-1 for Cu2+ ions and 226.88 mg g-1 for Ag + ions within 120 min. As real scenario, the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel exhibits excellent removal efficiencies for metallic ions even in the complicated media of actual electroplating wastewater. In addition, we explore the competitive adsorption order of metal cations by using experimental characterization and theoretical calculations. The optimal configuration of CTS-PEI is also discovered with the density functional theory, and the water retention within hydrogel is simulated through molecular dynamics modeling. We find that the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel could be reused and after 5 cycles of adsorption-desorption, removal efficiency could maintain 80%. Finally, the Ag+ accumulated by hydrogel are reduced to generate a photocatalyst for efficient degradation of Rhodamine B. The novel magnetic hydrogel paves a promising path for efficient removal of heavy metal ions in wastewater and further resource utilization as photocatalysts.

Green Synthesized Silver Nanoparticles Loaded in Polysaccharide Hydrogel Applied to Chronic Wound Healing in Mice Models

The prevalence of chronic wounds is increasing owing to the expanding population and the growing number of individuals suffering from diabetes. Such a chronic wound continues to be a significant healthcare burden for diabetic patients because it frequently carries a high chance of limb loss due to amputation and reduces survival as a result. Development of innovative wound dressing materials with the potential to stop bacterial infections and accelerate the process of tissue regeneration is needed to increase the effectiveness of diabetic wound healing. In the current study, a co-polymerization process based on a free radical reaction was used to create a hydrogel of polysaccharides blend graft acrylamide (PsB-g-Am). Starch, chitosan, and alginate make up the polysaccharides blend (PsB). The produced hydrogel's structure was characterized using FTIR spectroscopy. The antibacterial activities of silver nanoparticles synthesized through the green method using garlic bulb (Allium sativum) is reported. The silver nanoparticles' physical characteristics were examined using scanning electron microscopy, transmission electron microscopy analysis, and UV-visible spectroscopy and they were found to range in size from 50 to 100 nm. The agar well diffusion technique is used to investigate the antibacterial characteristics. Inclusion of silver nanoparticles in the hydrogels demonstrated concentration-dependent antibacterial behavior against Gram-negative Klebsiella pneumoniae and Gram-positive Staphylococcus aureus during antimicrobial testing of the hydrogels. When hydrogels were applied to diabetic mice, the system was examined for its healing abilities, and positive therapeutic results were obtained in as little as 14 days. Thus, it can be inferred that graft copolymer of chitosan-AgNPs hydrogels can promote healing in chronic wounds over time and can be utilized as an alternative to conventional therapies for chronic wounds (such as those brought on by diabetes) in mouse models.

A Comprehensive Review of Polysaccharide-Based Hydrogels as Promising Biomaterials

Polysaccharides have emerged as a promising material for hydrogel preparation due to their biocompatibility, biodegradability, and low cost. This review focuses on polysaccharide-based hydrogels' synthesis, characterization, and applications. The various synthetic methods used to prepare polysaccharide-based hydrogels are discussed. The characterization techniques are also highlighted to evaluate the physical and chemical properties of polysaccharide-based hydrogels. Finally, the applications of SAPs in various fields are discussed, along with their potential benefits and limitations. Due to environmental concerns, this review shows a growing interest in developing bio-sourced hydrogels made from natural materials such as polysaccharides. SAPs have many beneficial properties, including good mechanical and morphological properties, thermal stability, biocompatibility, biodegradability, non-toxicity, abundance, economic viability, and good swelling ability. However, some challenges remain to be overcome, such as limiting the formulation complexity of some SAPs and establishing a general protocol for calculating their water absorption and retention capacity. Furthermore, the development of SAPs requires a multidisciplinary approach and research should focus on improving their synthesis, modification, and characterization as well as exploring their potential applications. Biocompatibility, biodegradation, and the regulatory approval pathway of SAPs should be carefully evaluated to ensure their safety and efficacy.

Facile degradation of chitosan-sodium alginate-chromium (III) gel in relation to leather re-tanning and filling

Natural polysaccharide hydrogel, exemplified by chitosan‑sodium alginate (CS-SA), has been prevailing in adsorption of chromium (III) (Cr(III)) containing contaminant. However, the traditional desorption of CS-SA-Cr(III) to recycle the adsorbent faces the problems including chemical desorbents secondary pollution, resource waste of the terminal CS-SA adsorbents, and tedious work of reusing the desorbed Cr(III). Herein, the adsorption product, CS-SA-Cr(III) gel, was degraded to CS/SA/Cr(III) sol and applied in leather re-tanning and filling processes directly. To achieve this goal, three degradation methods were used to transform the gel to sol. Due to the excellent overall performance of the CS/SA/Cr(III)-HMD₄ sol (obtained by the hydrothermal-mechanical degradation method for 4 h (HMD₄)), including wide size and distribution range, moderate viscosity (54 ± 3.1 mPa·s), high electronegativity (-38.6 ± 5.8 mV), and good stability, the resultant leather after re-tanning and filling by the sol achieved fascinating properties such as good thermal stability (T_s, 116.8 ± 1.8 °C; T_d, 94.2 ± 1.7 °C), mechanical performance (tensile strength, 6.9 ± 0.52 MPa; elongation at break, 95 ± 3.0 %), and superduper thickening rate (31.8 %). Moreover, the mechanism of good re-tanning and filling effects was deciphered. Therefore, this work intends to overcome the limitation of traditional desorption technology and further realizes the high-valued application of the exhausted CS-SA-Cr(III) in leather re-tanning and filling processes.

Marrying the incompatible for better: Incorporation of hydrophobic payloads in superhydrophilic hydrogels

HYPOTHESIS

The entrapment of lyophobic in superhydrophilic hydrogels is challenging because of the intrinsic incompatibility between hydrophobic and hydrophilic molecules. To achieve such entrapment without affecting the hydrogel's formation, the electrospinning of nanodroplets or nanoparticles with a water-soluble polymer could reduce the incompatibility through the reduction of interfacial tension and the formation of a barrier film preventing coalescence or aggregation.

EXPERIMENTS

Nanodroplets or nanoparticles dispersion are electrospun in the presence of a hydrophilic polymer in hydrogel precursors. The dissolution of the hydrophilic nanofibers during electrospinning allows a redispersion of emulsion droplets and nanoparticles in the hydrogel's matrix.

FINDINGS

Superhydrophilic hydrogels with well-distributed hydrophobic nanodroplets or nanoparticles are obtained without detrimentally imparting the viscosity of hydrogel's precursors and the mechanical properties of the hydrogels. Compared with the incorporation of droplets without electrospinning, higher loadings of hydrophobic payload are achieved without premature leakage. This concept can be used to entrap hydrophobic agrochemicals, drugs, or antibacterial agents in simple hydrogels formulation.

Manufacture of non-thrombogenic polymer surfaces by gamma irradiation to induce simultaneous grafting and heparinization of thin PVC films

Investigations regarding alternative methods for producing polymeric materials with hydrophilic properties have increased considerably. In this context, polymeric biomaterials with hemocompatible surface properties have been successfully obtained by grafting hydrophilic monomers onto commercial polymer films by simultaneous irradiation processes. In this study, simultaneous irradiation and grafting were used to produce a copolymer PVC-co-DMAEMA-co-heparin with hemocompatible surface properties. Characterization by FTIR of the graft copolymer indicates that the increase in monomer grafting levels inhibits the bonding sites to heparin. FTIR-PAS analyses of the graft copolymers showed that the highest graft levels were obtained for the irradiated samples containing 45% of monomer. Heparin, however, could only be detected in the irradiated samples containing 30% of DMAEMA. The analysis of the micrographs, on the other hand, showed that increasing the monomer concentration enhances surface roughness of the graft copolymers. Roughness however decreased with heparin addition. It was possible to verify that an excess of surface roughness of the graft copolymers inhibits anticoagulant properties of heparin, triggering thrombus formation. Platelet adhesion, on its turn, was not significantly affected by the presence of heparin when PVC-co-DMAEMA and PVC-co-DMAEMA-co-heparin, obtained from the systems containing 45% of monomer, are compared. The addition of heparin in the systems containing 30% of DMAEMA resulted in fewer thrombogenic surfaces.

Smart nanotheranostic hydrogels for on-demand cancer management

Theranostics is a revolution in cancer therapy. Hydrogels have many implications as a drug delivery vehicle and theranostics hydrogels could be a model nanotherapeutic for simultaneous cancer diagnosis and treatment.

Compósitos en estado hidrogel con aplicación en la adsorción de metales pesados presentes en aguas residuales

La contaminación por metales pesados es un problema, que hoy en día no se ha logrado disminuir. Por esta razón, es necesario innovar constantemente las técnicas tradicionales con el fin de aplicar procesos eficientes que ayuden a remover los contaminantes e incluso recuperarlos para ser reincorporados a procesos productivos. En este contexto, la adsorción es una técnica tan versátil, que es viable su aplicación con materiales de diferentes características. Entre los materiales que han resultado adsorbentes eficientes, se encuentran las partículas inorgánicas y los polímeros/biopolímeros. Estos componentes por si solos presentan capacidades adsorbentes aceptables, pero en los últimos años se ha explorado la generación de matrices poliméricas en estado hidrogel reforzadas con materiales inorgánicos o mezclas de redes poliméricas generando compósitos, para mejorar o incrementar la capacidad de adsorción. Los hidrogeles compósitos conjugan una adsorción eficaz, buena área superficial específica y de fácil aplicabilidad, por lo que representan una gran alternativa para la disminución de los iones de metales pesados presentes en los ecosistemas acuáticos. Por este motivo, es la presente revisión de los materiales con propiedades adsorbentes, las estrategias para generar compósitos en estado hidrogel y sus propiedades adaptadas para la adsorción de iones de metales pesados, así como los retos y las áreas de oportunidad implícitos en esta generación de materiales innovadores. 

High-performance two-dimensional montmorillonite supported-poly(acrylamide-co-acrylic acid) hydrogel for dye removal

High-performance two-dimensional montmorillonite supported-poly (acrylamide-co-acrylic acid) hydrogel for dye removal was investigated. Montmorillonite cooperated with acrylamide and acrylic acid via polymerization, hydrogen-bond, amidation and electrostatic interactions to form the three-dimensional reticular-structured hydrogel with the free entrance for macromolecules. Adsorption tests revealed that the efficient removal (97%) for methylene blue at high concentration (200 mg/L) could be achieved via a small dose of hydrogel (0.5 g/L) within a short time (20 min). The excellent adsorption performance was profited from the electronegative surface and fully exposed reaction sites of two-dimensional montmorillonite, which could save the treatment cost and promote the removal effect compared with the conventional adsorbents. The adsorption process of methylene blue onto hydrogel could be fitted by both the pseudo-first-order and pseudo-second-order kinetics models, and the adsorption isotherm corresponded to the Sips model. The mechanism analysis based on Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements illustrated that the reaction between carboxyl groups and methylene blue molecules as well as the cation-exchange enabled the hydrogel performing extraordinary adsorption efficiency.

Equilibrium and kinetic studies for silver removal from aqueous solution by hybrid hydrogels

Hybrid hydrogels were prepared by blending Carboxymethyl chitosan (CMCts), Carboxymethyl cellulose (CMC) with Sodium sulfonate styrene (SSS) by 60-kGy gamma rays. The prepared hydrogels were utilized as silver-ion (Ag) sorbent under non- and competitive cases. Batch adsorption experiments were conducted in functional conditions including contact time, ratios of (CMC:CMCts) and SSS, pH value, temperature and adsorbent weight. Equilibrium contact time of 10 h. was obtained by the adsorption material. The optimal 4:2 ratio of (CMC:CMCts):SSS showed the Ag highest adsorption efficiency. The maximum percentage of Ag⁺ removal was achieved at the pH 5. The temperature effect on the adsorption ability of hybrid hydrogel indicated the Ag adsorption process was endothermic and spontaneous. The Langmuir isotherm model fitted Ag adsorption data well, assuming a monolayer adsorption with predicted maximum adsorption capacity of 451.74 × 10^-3 mg. g^-1. From the kinetic data, the process of Ag adsorption had higher agreement with the pseudo-2nd order model, predicting the amount of Ag⁺ uptake at different contact time intervals and at equilibrium.