Green recovery and optimization of hemicellulose extraction from black liquor using acetic acid and cyclopentyl methyl ether

Hemicellulose, the second most abundant polysaccharide in lignocellulosic biomass, is a valuable raw material for producing value-added products such as furfurals, biofuels, and additives for the food and paper industries. This study presents a greener approach to recover hemicellulose from black liquor (BL), a byproduct of kraft pulping process, while optimizing the recovery conditions to enhance yield and purity. This separation was achieved by acidifying BL using glacial acetic acid. However, since lignin, the most abundant organic component in BL, also precipitates as the pH decreases, a green organic solvent, cyclopentyl methyl ether (CPME), was used to minimize lignin co-precipitation. A series of experiments were performed, varying temperature (20–70 °C), pH (2.6–3.2), and the CPME-to-BL ratio (1:1–3:1) to determine optimal conditions for hemicellulose recovery. The highest hemicellulose yield (∼78 %, with ∼60 % purity) was obtained at 45°C with a CPME-to-BL ratio of 2:1. On the other hand, the highest purity (∼68 %, with ∼70 % yield) was achieved at 20°C under the same ratio. In both cases, acidification was carried out to a pH between 2 and 3. The recovered hemicellulose was analyzed using HPLC technique, which confirmed that approximately 80 % of the total sugar content was xylose, indicating that the recovered hemicellulose was predominantly xylan. Additionally, to improve the sustainability of the process, approximately 78 % of the CPME was recovered using rotary evaporation under vacuum. Overall, this study demonstrated an efficient, green and economically viable process for the recovery of hemicellulose from BL. • Hemicellulose recovery from black liquor using acetic acid and CPME, a green solvent. • CPME reduces lignin co-precipitation, improving hemicellulose purity and recovery efficiency. • Optimization improves hemicellulose yield and purity for more efficient recovery. • ∼78 % CPME recovered, demonstrating an eco-friendly and sustainable process design.