Nanocellulose prepared with γ-valerolactone pretreatment and its enhancement in colored paper

New techniques are always demanded to pursuit green and economical ways for nanocellulose preparation. We herein proposed to use γ-valerolactone (GVL) to facilitate the nanocellulose preparation from bleached bamboo pulp fibers as a green and sustainable pretreatment. The GVL pretreatment caused the bamboo fibers to destruct, resulting in an obviously increased fine fiber content, which was systematically studied to disclose the influence of different factors on the fiber changes. The optimum GVL pretreatment conditions were determined as reaction time of 4 h, reaction temperature of 140 °C and the ratio of GVL to water of 4:1. Notably, the GVL pretreatment caused negligible changes in the functional groups on cellulose, as well as its crystalline structure. The resultant nanocellulose (i.e. G-CNF) had a width of ca. 47 nm and it showed good adsorption capacity towards RR195 dye since an impressive dye uptake rate of 46.81 % was attained. The incorporation of G-CNF significantly improved the coloring performance and the ∆E (color difference) value reached up to 33.73. Improvements in the mechanical properties of RR195 dyed paper were also observed with the incorporation of G-CNF. This work sheds light on the nanocellulose preparation with GVL pretreatment and demonstrates a feasible way to apply the resultant nanocellulose in the colored paper manufacture.