Super-swollen hydrogels were prepared in vitro from lignocelluloses of various origins via direct dissolving in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) followed by regeneration from solutions. The hydrogels retained a large amount of water (up to 2500 wt%) and had high porosity and specific surface areas. Superabsorbance of the hydrogels was confirmed with a wide angle X-ray scattering method. The hydrogels seem to be smart matters due to PH-dependent behavior by swelling and pH change experiments. The gelation mechanism includes spontaneous self-assembly from the solutions in DMAc/LiCl, due to the reconstruction of new hydrogen bond webs between lignocellulose chains and water. The hydrogels exhibited high stability but their morphology changed while drying due to water removal and the collapse of the H-bonds.

A comparative study of crystallinity and size of cellulose crystallites of powder celluloses from hardwood pulp, flax fibers and cellulose hydrogels was performed by the wide-angle X-ray scattering method (WAXS). Cellulose hydrogels were prepared by regeneration from solutions of powder celluloses in DMAc/LiCl. The variation in the structural characteristics of the swollen hydrogels and the freeze-dried hydrogels, alongside the powder celluloses, was studied. The swollen hydrogels contained over 97 mass% water, and thus their WAXS patterns resembled those of water. The WAXS patterns for both powder celluloses indicated cellulose I structure, whereas the freeze-dried hydrogels revealed cellulose II polymorph. The impact of the calculation mode on the obtained crystallinity values was investigated using three analysis methods. The Segal method could be used only for cellulose I samples, whereas amorphous fitting and amorphous subtraction methods could be applied for both samples, cellulose I and II. The Segal method gave the highest crystallinity values, while the amorphous fitting and the amorphous subtraction generated similar values. The advantages of using the amorphous fitting method and the effect of drying on the structure of the hydrogels were discussed.

Utilization of paper wastes as renewable resource of lignocellulosic constituents has the opportunity to promote a cleaner environment and to prepare valuable materials. This paper describes our study on an isolation of low-fiber powder cellulose from two grades of wastes as feedstocks: waste newsprint paper and cardboard wrapper through recycling including a thermal defibration, an alkali treatment with a solution of NaOH with a concentration from 0.03 to 1.00 М, a bleaching with a solution of Н2О2 with a concentration from 0.8 to 2.6 М followed with an acid hydrolysis of the pretreated species with a solution of HNO3 of 1.5 and 3.0 M. An impact of the pretreatment on sizes of fibers was evaluated with a stereoscopic microscopy. The powder celluloses obtained as a result of the acid hydrolysis exhibited the structure of cellulose I revealed with a WAXS method and were of a high-grade purity, according to EDXA. Sorption capacities of the powder celluloses from the waste cardboard and newsprint towards a dye methylene blue were 6.67 mg∙g-1 and 8.75 mg∙g-1 correspondingly.