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

Abstract

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, LignoForce™ 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 LignoForce™ 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 chemical-mechanical pulping effluent (CMPE) of wheat straw were compared and analyzed to evaluate the feasibility of the improved LignoForce™ technology utilized in non-wood BMPE with high extraction efficiency. The study found that the practical successive LignoForce™ 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.