Process optimization and recyclable utilization of organic solvent for the green degumming of hemp

Organic solvents are emerging green chemical reagents for the extraction of cellulose fibers, most of which are non-toxic, highly effective, and eco-friendly. However, the high costs of reagents and the disposal of degumming black liquors remain challenges. This research firstly investigated the optimal one-step extraction condition for hemp fibers and the recovery possibility of Ethylene Glycol (EG) solvent by vacuum distillation. Specifically, the effect of recovery and reuse rate of solvents of degumming black liquor was appraised. The results indicated that solvent recovery rates from three consecutive vacuum distillations reached 95.65 %, 93.02 %, 92.86 %, respectively, indicating a superior solvent recovery. Specifically, the effect of reuse times of recovery solutions on surface morphology, chemical composition, and cellulose crystallinity of degummed fibers was systematically evaluated, indicating that recycled solvents still maintained effective ability similar to original EG for separation of non-cellulosic materials in raw hemp. Compared with the traditional alkaline method (TAL), the treated fibers achieved a higher cellulose content of 83.01–90.23 %, fiber yield of 60.50–64.10 %, and tenacity of 6.04–6.25 cN/dtex, fulfilling the requirements of the national standards and further spinning process. To sum up, this study demonstrated that the recycling degumming of hemp with organic solvent is of great potential for cellulose fiber extraction with less chemical and energy usage, environmental pollution, as well as high efficiency, which realized further recycle economy and sustainable development.