Study of the effects of DES-like mixtures on the properties of unbleached softwood kraft pulp

Abstract

The scientific community has been drawn to variations of the processes aimed at obtaining cellulosic fibers. Deep eutectic solvents-like mixtures have been shown to be a potential and green replacement for pulping processes where, in addition to cellulose fibers, lignin and hemicellulose are obtained as by-products. In this research, the treatment of softwood kraft pulp using deep eutectic solvents-like mixtures based on choline chloride and lactic acid was studied. We chose the temperature, the ratio of deep eutectic solvents-like mixtures to the input unbleached pulp, and the molar ratio between the components in the solvent as the studied operating conditions. As part of the chemical characterization, we analyzed the Kappa number, which indicates the remaining lignin in the fibers, followed by the calculation of the treatment efficiency. In addition, this process made it possible to obtain solid pulp under different conditions, which were characterized by analytical, optical, and spectrometric methods. The Kappa number of the delignified fibers ranged from 9.59 when using deep eutectic solvents-like mixtures in a ratio 1:9 (1 h; 120 °C; 1:10) to 20.88 (choline chloride/lactic acid 1:6; 1 h; 80 °C; 1:5), which represents treatment efficiency values from 6.79 % to 57.19 %.

Keywords

• DES-like mixtures
• Unbleached pulp
• Choline chloride
• Lactic acid
• Green solvents
• Treatment