Efficient separation of catechyl lignin from castor seed coats via molten salt hydrate

The excellent acid-resistant property of catechyl lignin (C-lignin) allows for its isolation from biomass with intact structure, making it an "ideal lignin" for valorization. In this study, an effective method was developed to separate C-lignin from castor seed coats using acidic molten salt hydrate of LiBr (LiBr-AMSH). Under recommended conditions (60 wt% LiBr solution with 60 mM HCl, 150 °C, and 1 h), 96 wt% of solid sample (based on Klason lignin in castor seed coats) was obtained. Structural characterization indicated that isolated C-lignin consisted of 99 % benzodioxane (BD) structures. Additionally, the optimal conditions led to the achievement of a C-lignin yield of 12.8 wt% (based on raw material), demonstrating a notable accomplishment in terms of productivity. This study provides a green and efficient procedure for extracting C-lignin from castor seed coats while paving the way for valorization.