Thermally stable cellulose nanospheres prepared from office waste paper by complete removal of hydrolyzed sulfate groups.

Cellulose nanocrystals are commonly obtained by acid hydrolysis, particularly with H2SO4. However, a small amount of deposited sulfate-groups contributes to the degradation of their thermal stability. This study prepared thermally-stable and sulfate-group-free cellulose nanospheres (CNSs) from office waste paper by H2SO4 hydrolysis followed by solvolytic desulfation. The optimal desulfation conditions (i.e., 5 wt% MeOH, reaction temperature of 90 °C, a reaction time of 20 min, 0.5 mM pyridine) were preliminarily found from a one-factor-at-a-time experiment and validated by the results of a central composite design. The optimal desulfation conditions promoted environmental sustainability with less pyridine and MeOH and comparably shorter reaction time. The desulfated CNSs had a significant thermal stability enhancement from 186 to 340 °C. Comprehensive characterization of the morphology, chemical composition, and thermal behavior of the desulfated CNSs reconfirmed the complete removal of sulfate groups without harmful pyridine residues, demonstrating the potential use of the thermally stable CNSs.

Synthesis of cellulose-g-poly(acrylic acid) with high water absorbency using pineapple-leaf extracted cellulose fibers.

This study synthesized cellulose-g-poly(acrylic acid) with high water absorbency using the cellulose extracted from pineapple leaves. The synthesis experiment used a novel combination of ethylene glycol dimethacrylate (EGDMA) and azobisisobutyronitrile (AIBN) as the cross-linker and the initiator, respectively. Experimental results showed that the concentrations of AIBN and EGDMA had significant effects on the structure and the water absorbency of the cross-linked materials. The cellulose-g-poly(acrylic acid) synthesized with 0.5 wt% AIBN and 0.5 wt% EGDMA had an excellent swelling capacity of 1900 g/g in distilled water, significantly larger than previously reported ones. Compared with poly(acrylic acid), the cross-linked product demonstrated an absorbency improvement of 1.65 times in distilled water and 1.27 times in 8.6 ppm NaCl solution that was the highest salinity level in Ben Tre, Vietnam, in March 2020. Therefore, the obtained product showed high potential for agricultural applications, especially in coastal regions facing a growing thread of saltwater intrusion.