Evaluation of Filter Press Performance for Extracting Lignin from Acid-based Black Liquor

Lignin, extracted from the black liquor of the pulping process, is one of abundant renewable biopolymers and is considered a potential alternative to petroleum-based compounds. Currently, research focusing on the utilization of technical lignin is increasing, leading to a growing demand for lignin for commercial applications. Therefore, research on efficient dehydration to obtain lignin from black liquor with a simple pretreatment process is essential. This study used fast and simple mechanical dehydration in a filter press as an alternative to efficiently isolate lignin from black liquor. An acidic black liquor was used as the feedstock, which does not require a pH adjustment process, unlike the alkaline black liquor coming out of the kraft pulping process. As a result, a high degree of lignin purity (87.2‒89.2%) can be extracted, which is comparable to technical lignin. Furthermore, the molecular weight and polydispersity of the extracted lignin are constant, regardless of whether it is washed, which supports the performance of the filter press and filter cloth used in this study to produce homogeneous lignin. These findings demonstrate the potential of the filter press dewatering process for commercial-scale lignin production. © 2025 Korean Technical Assoc. of the Pulp and Paper Industry. All rights reserved.