Delignification from Geodae-Uksae1 using soda-pulping followed by evaluation on recycling of liquid-liquid extraction solvent

In this study, lignin, monomeric sugars, and organic acids are separated effectively from Geodae-Uksae1 (GU1, Miscanthus spp) using various processes such as soda-pulping, liquid-liquid extraction (LLE), and distillation. Soda-pulping is performed using a 1 L rocking reactor at a liquid-solid ratio of 8:1, temperature of 170 °C, H-factor of 900 (the H-factor is a function of time and temperature), and NaOH concentrations of 10 g kg−1, 40 g kg−1, and 80 g kg−1, the experiment condition for highest pulp and delignification yields is approximately 64.0% and 78.6% at 10 g kg−1 and 20 g kg−1 NaOH, respectively. The hydrolyzate derived using soda-pulping and acid hydrolysis carried out LLE with liquid-liquid solvents (LLESs) as tri-octyl phosphine oxide (TOPO) and tri-alkyl phosphine oxide (TAPO). Afterwards, the used LLESs in LLE process are performed on distillation process and reused at LLE process. These results showed that the extraction efficiency of acetic acid using TOPO and TAPO decreased to 33.1% 23.5% at the number of recycled tenth times, respectively. In addition, the extraction efficiency of acetic acid using TOPO and TAPO after washing with 40 g kg−1 NaOH solution are 66.31% and 67.99% at the number of recycled tenth times, respectively. Through recycling of LLESs, washing treatment using alkaline solution is necessary process in recycling process of LLESs.