A facile process for efficient extraction of lignin with controllable morphology from wheat straw based bio-mechanical pulping effluent

The main non-wood lignocellulose resource, wheat straw, has been utilized in bio-mechanical pulping process for paper industry to alleviate feedstock shortages, reduce environmental pollution, and lower carbon emissions as well. However, the wheat straw-based bio-mechanical pulping effluent (BMPE) could cause water pollution and resource waste if not properly handled. The efficient extraction of lignin biomass from BMPE is still a great challenge. The novelty of this study is to propose a facile process for efficient extraction of lignin with high yield, high purity and controllable morphology from wheat straw based BMPE via a commercialized technique, LignoForceTM process, which has been industrially applied in lignin extraction from wood based Kraft pulping black liquor. Considering the unique attributes of wheat straw (non-wood) based BMPE, we successfully improved the LignoForceTM technology for high efficient lignin extraction. The extracted lignin from BMPE was characterized for its chemical properties, ash content, monosaccharide composition, controllable morphology, particle size/distribution, and molecule weight/distribution at varying oxygen dosages and oxidation temperatures. The resultant lignin particles possess comparable regular spherical morphology with controllable particle size/ distribution. Additionally, the yield and ash content of the lignin extracted from BMPE and chemicalmechanical pulping effluent (CMPE) of wheat straw were compared and analyzed to evaluate the feasibility of the improved LignoForceTM technology utilized in non-wood BMPE with high extraction efficiency. The study found that the practical successive LignoForceTM treatments, including oxidation process (O2), CO2, and H2SO4 acidification procedures, showed great potential in obtaining high-yield and high-quality acid-precipitated lignin with controllable morphology from the non-wood (wheat straw) based BMPE.