Acidic deep eutectic solvent treatment for viscosity control and reactivity enhancement of bamboo dissolving pulp

This work demonstrated a green process using deep eutectic solvent (DES) treatment for properties improvements of bamboo dissolving pulp. Results showed that an acidic DES, namely choline chloride-oxalic acid, was the most effective compared to other acidic, alkaline and neutral DESs. Upon the optimum acidic DES treatment (pulp to DES ratio 1:10, 60 degrees C and 30 min), the pulp viscosity was reduced from 715 mL/g of original pulp to 466 mL/g, while the pulp reactivity increased from 43.0 to 88.1%. The positive results were mainly ascribed to a synergy during the DES treatment: (1) a large number of activated protons (H+) from the acidic DES depolymerized the cellulose chain and destroyed the fiber structure; (2) the vigorous hydrogen bonding competitions between fibers and DES (Ch(+) and Cl-) facilitated the fiber swelling and reaction efficiency, thus increasing fiber accessibility/reactivity. DES also featured a high recyclability/reusability after serval reuses. Therefore, this work offers a sustainable and effective alternative for production of premium bamboo dissolving pulp. [Graphics]