pH‐responsive gum tragacanth hydrogels for high methylene blue adsorption

Abstract

BackgroundBiobased hydrogels are used in many applications due to their easy availability, low cost and versatility to acquire different structures. However, there is scarce information about the changes generated in the matrix's microstructure after crosslinking reactions. The effect of the crosslinking reaction using glutaraldehyde on the micro and macrostructure of tragacanth gum hydrogels (TG GLU) was evaluated.ResultsNew acetal groups, that increase with increasing GLU, produced less packed biopolymeric structures with more thermal stability. Due to demethoxylation, a higher amount of free carboxylic groups after crosslinking reaction were determined in TG GLU. Crosslinked hydrogels presented a higher water uptake capacity with a pH responsive behavior with suitable thermal and mechanical properties. Besides, the highest adsorptive capacity of methylene blue achieved was qm=530 mg/g.ConclusionspH responsible gels from tragacanth were obtained after crosslinking with glutaraldehyde. Chemical and microstructural changes affect the Methylene Blue adsorption, resulting in hydrogels with improved adsorptive properties. These properties give the TG‐GLU hydrogels some features that make them suitable for practical applications related to the pharmaceutical industry for drug delivery and water remediation.This article is protected by copyright. All rights reserved.

Physical and Chemical Properties of Pachycymbiola brasiliana Eggshells—From Application to Separative Processes

“…Chitosan membranes crosslinked with glutaraldehyde exhibit high water sorption [19]. Similar results have been found for tragacanth-glutaraldehyde films [28]. According to Beppu et al [19], chitosan ions decrease the permeability compared to crosslinked chitosan.…”

“…From a kinetic point of view, PBn water sorption displays three stages, similar to that of chemically crosslinked films [28] at a constant temperature (Figure 8). An increase in mass can be observed due to the water vapor permeability, with a value of 3.74 ng m/m 2 s Pa.…”

“…According to the SEM observations, the surface of the film is rough, with regular indentations of a similar size between 0.2 and 0.7 µm long by approximately 0.1 µm wide (see Figure 6). Chitin whiskers indicate the surface uniformity of the film as significantly improved, and display a smooth and dense structure [27][28][29]. The EDX analysis shows the presence of C, O, and N distributed uniformly within the membrane.…”

“…The gel theory assumes that the rigidity of the polymer network comes from its three-dimensional structure, so the plasticizers act by breaking the polymer-polymer interactions, that is, by interposing themselves between the macromolecular chains. The free volume theory considers the addition of plasticizers as a way to increase the free volume, reducing the interactions between the chains [24][25][26][27][28].…”

“…From a kinetic point of view, PBn water sorption displays three stages, similar to that of chemically crosslinked films [28]: the first stage (during the first 30 min of immersion in water), when the sorption phenomenon responds to the first-order kinetics; the intermediate step (between 30 min and 75 min), when the water sorption reaches equilibrium; and finally, the zero-order stage of desorption (for times longer than 75 min).…”