Effect of borax addition on the structural modification of bentonite in biodegradable alginate-based biocomposites

Studying structural and rheological properties of alginate-whey protein isolate cold-set hybrid emulgels at various pH levels

Effects of different pH values (4-7) and whey protein isolate (WPI) concentrations (0.5-1.5%) were evaluated on physical, mechanical, and rheological properties of cold-set alginate-based soybean oil hybrid emulgels. The pH value changes were more effective than WPI concentration changes on emulgel properties. According to syneresis and texture profile analysis results, 1% WPI was selected as the optimum concentration. The XRD analysis showed that calcium alginate (CA) emulgel at pH 6 had a different peak at 2θ of 14.8°, likely indicating the highest amount of ion-bridging and maximum number of junction zones. The homogeneity of CA and CA + WPI emulgels (determined by image entropy analysis) decreased by pH reduction from 7 to 4, which can be related to acid-induced intermolecular interactions between alginate chains. The rheological properties of CA and CA + WPI emulgels revealed predominant elastic character (G' > G'') at different pH values. Creep test results showed that the relative recovery of emulgel prepared at pH 7 and 5 was 18.10 and 63.83%, respectively, suggesting pH reduction contributed to increase in the elastic component of material. The findings of this study can be applied for developing structured cold-set emulgels as solid fat replacers in meat and dairy products.

Green Conductive Hydrogel Electrolyte with Self-Healing Ability and Temperature Adaptability for Flexible Supercapacitors

Conductive hydrogels (CHs) are ideal electrolyte materials for the preparation of flexible supercapacitors (FSCs) due to their excellent electrochemical properties, mechanical properties, and deformation restorability. However, most of the reported CHs are prepared by the chemical crosslinking of synthetic polymers and thus usually display the disadvantages of poor self-healing abilities and nonadaptability at environmental temperatures, which greatly limits their application. To overcome these problems, in the present work, we constructed a sodium alginate-borax/gelatin double-network conductive hydrogel (CH) by a dynamic crosslinking between sodium alginate (SA) and borax via borate bonds and hydrogen bonding between amino acids in gelatin and SA chains. The CH displays an excellent elongation of 305.7% and fast self-healing behavior in 60 s. Furthermore, a phase-change material (PCM), Na₂SO₄·10H₂O, was introduced into the CH, which, combined with the nucleation effect of borax, improved the ionic conductivity and temperature adaptability of the CH. The flexible supercapacitor (FSC) assembled with the obtained CH as the electrolyte exhibits a high specific capacitance of 185.3 F·g^-1 at a current density of 0.25 A·g^-1 and good stability with 84% capacitance retention after 10 000 cycles and excellent temperature tolerance with a resistance variation of 2.11 Ω in the temperature range of -20-60 °C. This green CH shows great application potential as an electrolyte for FSCs, and the preparation method can be potentially expanded to the fabrication of self-repairing FSCs with good temperature adaptabilities.

Bioformulation of Microbial Fertilizer Based on Clay and Alginate Encapsulation

This study aims to develop new formulations for microbial fertilizers Pseudomonas fluorescens Ms-01 (Pf) and Azosprillum brasilense DSM1690 (Ab) using two kinds of clay minerals. The studied formulations were prepared as hybrid materials based on halloysite and alginate [Ha-Ag] or montmorillonite and alginate polymers [Mt-Ag] and were applied to the bacterial strains to develop low cost, efficient, and slow-release capsules. Their efficiency was evaluated in comparison with alginate [Ag] as the control. The produced capsules were spherical in shape and were chemically and physically characterized and further analyzed for their swelling ratios, soil biodegradability, release kinetics of microbial cells, and their survival stability over 3 months of storage under different conditions (room temperature vs 4 °C). The effect of the capsules on the growth of wheat plants was also investigated. Results showed that both formulations were able to preserve bacterial survival which reached 14.8 log CFU g^-1 after 3 months storage in the halloysite formulation. The swelling ratios were ranged between 61.5 ± 1.35% and 36.5 ± 5% for the montmorillonite and the halloysite formulations, respectively. The release kinetics revealed the slow-release capacity of the capsules mainly with the halloysite formulation which significantly released bacterial cells after 15 days of incubation in saline water (15.24 log CFU mL^-1). The application of the capsules to wheat plants significantly increased root and shoot biomasses and nitrogen content in the roots. In conclusion, halloysite minerals seem to be more adapted as additive to alginate in microbial encapsulation.

Enhanced performance and interfacial investigation of mineral-based composite phase change materials for thermal energy storage

A novel mineral-based composite phase change materials (PCMs) was prepared via vacuum impregnation method assisted with microwave-acid treatment of the graphite (G) and bentonite (B) mixture. Graphite and microwave-acid treated bentonite mixture (GBm) had more loading capacity and higher crystallinity of stearic acid (SA) in the SA/GBm composite. The SA/GBm composite showed an enhanced thermal storage capacity, latent heats for melting and freezing (84.64 and 84.14 J/g) was higher than those of SA/B sample (48.43 and 47.13 J/g, respectively). Addition of graphite was beneficial to the enhancement in thermal conductivity of the SA/GBm composite, which could reach 0.77 W/m K, 31% higher than SA/B and 196% than pure SA. Furthermore, atomic-level interfaces between SA and support surfaces were depicted, and the mechanism of enhanced thermal storage properties was in detail investigated.