Tannins are phenolic compounds with considerable abundance in nature. They have attracted significant attention lately owing to their huge variety of potential applications. Accordingly, the tannin-related activity in terms of research has undergone a great boost, especially as green feedstock for materials in several fields. Nevertheless, the extraction process remains as the main bottleneck for their valorization, due to their heterogeneous nature. In the present review, a comprehensive study of the main types of tannins extraction techniques was carried out based on the works from the last 20 years. The literature review was carried through analysis of an initial sample of works followed by snowballing process, obtaining the main extraction parameters of each method. Thereby, the different tannins extraction methods were assessed and their major strengths and weaknesses elucidated. Moreover, a direct comparison between the different techniques was done, leading to the main prospectives for the efficient and clean tannins extraction and production.
We compared the enzymatic attack by an active cellulase preparation on native cotton, swollen cotton, and regenerated cellulose. At various time intervals the residual cellulose was analyzed for: weight loss, number‐average degree of polymerization, weight‐average degree of polymerization, water retention value, and the biometric length distribution of the fibers; morphologic aspects were analyzed at various intervals of time. On the solubilized part glucose and reducing sugars were estimated. All the data obtained at the supramolecular and macromolecular level were consistent with the existence of several enzymic factors responsible for the hydrolysis of these different substrates.
The objective of this work is to compare three techniques for characterizing the morphology of porous bio-based carbon foam, namely mercury intrusion porosimetry, scanning electron microscopy and X-ray microtomography.
The applicability of the sedimentation velocity method for the determination of molecular weight distributions of synthetic, stereoregular tribenzyl glucans was investigated. Moderate to severe dependencies on pressure and concentrations, accompanied by diffusion, were observed with two polymers of low to medium polydispersity. The corrections for these effects were applied in a sequential manner, treating each effect independently from others. Polydispersities obtained from the corrected sedimentation coefficient distributions compared favorably with polydispersities obtained by independent methods. The synthesis of stereoregular linear a-l,6-linked polysaccharides is under detailed investigation at this laboratory.1-10 These studies have created a need for a relatively rapid and reliable method for the characterization of molecular weight distributions of the polymers. The requirements of the method include applicability to both the water-soluble parent polysaccharides and their derivatives soluble only in organic solvents, to molecular weight distributions of both narrow as well as moderate polydispersity, and to solutions not at their temperature. Of a number of possible experimental techniques available for this purpose, the method of sedimentation velocity was investigated first. The latter technique has been used in the characterization of a number of synthetic polymers with apparent success, especially with polymers of narrow polydispersity and under conditions.11-16 In addition, the theory of sedimentation velocity is well understood.17In the following, we report on the application of the sedi-
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