Parameters Affecting the Cross-Flow Filtration of Dissolved LignoBoost Kraft Lignin

Abstract

In the kraft pulping process, the lignin-containing by-product kraft black liquor is currently combusted as an energy source. LignoBoost is a technique that extracts lignin from kraft black liquor, resulting in a lignin-lean black liquor, which is returned to the process, and an extracted kraft lignin. To facilitate the use of the extracted kraft lignin in high-value applications, it can be refined via fractionation to produce a more homogeneous starting raw material. Hence, the aim of this study is to investigate the behavior of dissolved softwood kraft lignin during cross-flow filtration. The effects of the lignin concentration, pH, and ionic strength on the fractionation of the dissolved lignin during cross-flow filtration are investigated. The results indicate that large amounts of low-molecular-weight kraft lignin can be produced from solutions having a low lignin concentration. Furthermore, the effects of pH and ionic strength on the fractionation of low-molecular-weight lignin are identified within the studied ranges.