PERFORMANCE OF UREA/NaOH AS A GREEN SOLVENT IN DISSOLVING RECYCLED CELLULOSIC FIBER FINES RESIDUES

Abstract

Using lignocellulosic materials for producing more value-added bioproducts is an attractive mission. Fiber fines, which represent an important part of the wastes generated by paper recycling mills, have been considered in the current research. Dissolving these lignocellulosic residues in environmentally friendly and inexpensive solvents can be a great achievement. For this purpose, the performance of urea/sodium hydroxide in dissolving printing and writing pulp (RPW) fines was investigated. Although using sodium hydroxide alone had a positive effect on the dissolution of recycled printing and writing pulp (RPWP) fines, the addition of urea increased the dissolution of fines from 23% to 56%. Different levels of urea consumption had no significant effect on the dissolving process. The performance of the urea/sodium hydroxide system in dissolving fines suspensions with different concentration (1, 3 and 5%) showed that reducing the concentration leads to an increase in fines dissolution (56, 36 and 7%, respectively). The results of FTIR confirmed the presence of cellulose without any hemicelluloses and lignin in the dissolving part. The results of X-ray diffraction analysis of soluble cellulose showed that the type-I cellulose structure probably changed to type-II cellulose. No reduction in the DP of dissolved cellulose and the integrated structure of the final cellulosic film confirmed by the FE-SEM images affirmed the successful dissolution of the RPWP fines in this system.