DES-like mixtures based on choline chloride and lactic acid for fractionation of hemp fibers

Hemp fibers are promising biomaterials that have many advantages, such as biodegradability, low production costs, and rapid growth. They can be used as alternatives to other cellulosic fibers that have higher environmental impacts. However, to use hemp fibers effectively, they need to be separated from the lignin in the hemp biomass. This process is called delignification, and it is usually done by using harsh chemicals that are harmful to the environment and human health. In this work, we used a new and green solvent, called deep eutectic solvent-like mixtures, to delignify hemp biomass. Deep eutectic solvent-like mixtures are made from choline chloride and lactic acid, which are cheap, safe, and biodegradable. We tested different combinations of temperature (80-160°C), time (60-240 min.), and solvent amount (1:10-1:60) to find the best conditions for delignification. We measured the Kappa number, which indicates how much lignin is left in the fibers, and the efficiency of delignification, which indicates how much lignin is removed. The Kappa number of delignified hemp fibers ranged from 10.7 (144°C, 204 min, 1:30) to 21.8 (160°C, 150 min, 1:17). The results showed that the optimal conditions to obtain the smallest Kappa number representing 6.6 are the boundary conditions of 160°C, 240 min, and a ratio of 1:60. This method is more sustainable and environmentally friendly than the conventional methods, and it can help achieve the goal of sustainable development for mankind.