Urea intercalated encapsulated microalgae composite hydrogels for slow-release fertilizers.

In agriculture, hydrogels can be addressed for effective operation of water and controlled-release fertilizers. Hydrogels have a significant ability for retaining water and improving nutrient availability in soil, enhancing plant growth while reducing water and fertilizer usage. This work aimed to prepare a hydrogel composite based on microalgae and biopolymers including chitosan and starch for use as a soil conditioner. The hydrogel composite was characterized by FTIR, XRD, and SEM. All hydrogel properties were studied including swelling degree, biodegradability, water-holding capacity, water retention, and re-swelling capacity in soil and water. The urea fertilizer loading and releasing behavior of the prepared hydrogels were investigated. The results revealed that the range of the maximal urea loading was between 99 and 440%, and the kinetics of loading was fitted with Freundlich model. The urea release % exhibited 78-95%, after 30 days, and the kinetics of release was fitted with zero-order, Higuchi, and Korsmeyer-Peppas models. Furthermore, the prepared hydrogels obtained a significant water-holding capacity, after blending soil (50 g) with small amount of hydrogels (1 g), the capacity increased in the range of 99.4-101.5%. In sum, the prepared hydrogels have the potential to be applied as a soil conditioner.

Eco-friendly and biodegradable sodium alginate/quaternized chitosan hydrogel for controlled release of urea and its antimicrobial activity.

Hydrogels could be employed in agriculture for efficient management of water and controlled-release urea (CRU). This study aimed to synthesize a superabsorbent hydrogel for CRU by cross-linking sodium alginate (Alg) and N-(2-hydroxy-3-trimethyl ammonium) propyl chitosan chloride (HTACC). The hydrogel structure was characterized by various techniques, and the urea loading and releasing behaviors of the synthetic hydrogels were investigated. The results revealed that the maximum urea loading ranged between 107 and 200%, and that the urea loading kinetics fitted with Langmuir model followed by the Freundlich model. The urea release behavior reached equilibrium after 30 days and urea releasing kinetics fitted with the zero-order and Higuchi models. The synthesized hydrogels exerted significant antimicrobial activities and molecular docking showed their binding affinity toward glucosamine-6-phosphate synthase, ß-lactamase II, TraR binding site and nucleoside diphosphate kinase. In conclusion, these Alg/HTACC hydrogels showed swelling, urea release, and antimicrobial properties suitable to meet the plant requirements and produce economic and environmental benefits.

Synthesis, characterization and antimicrobial activity of Schiff bases modified chitosan-graft-poly(acrylonitrile).

Graft copolymerization of chitosan (Ch) with acrylonitrile (AN) prepared by free radical polymerization using potassium persulfate (PPS) as initiator. Optimization of Graft copolymerization of acrylonitrile on to chitosan was performed by studying the main parameters that affecting the grafting process such as initiator and monomer concentrations, reaction time and temperature of the polymerization process to study their influence on percent grafting (G%), grafting efficiency (GE%) and percent homopolymer (H%). Modification of grafted chitosan was done by Schiff's base derivatives using different aldehydes. They are characterized by FT-IR, X-ray diffraction, thermal analysis and scanning electron microscope. Their antibacterial activities against Streptococcus pneumonia (RCMB 010010), Staphylococcus aureus (RCMB 010028), as Gram-positive bacteria and Escherichia coli (RCMB 010052) as Gram-negative bacteria and the antifungal activity against Aspergillus fumigatus (RCMB 02568), Candida albicans (RCMB 05036) and Geotricum candidum (RCMB 05097) were examined using the diffusion agar technique. The obtained data proved that modified chitosan by grafting show better antimicrobial activities than Chitosan. Also Schiff base derivatives showed better antimicrobial activities than grafted chitosan.