Different value-added products can be produced from lignin. To produce lignin based products, lignin derivatives need to be isolated from pulping spent liquors, as pulping spent liquors are dilute in lignin and impure. In this chapter, methods for isolating lignin derivatives from pulping spent liquors are reviewed. The main challenges and perspectives in the development of viable lignin production processes are described. LignoBoost and LignoForce were designed based on the acidification concept to isolate Kraft lignin from black liquor on the commercial scale, both of which produce pure lignin. To extract lignosulfonate from sulfite spent liquors, ultrafiltration seemed to be an industrially viable method, but the extracted lignin will likely contain impurities. Laboratory studies on adsorption and flocculation techniques for isolating lignin from other spent liquors with a low lignin content, e.g. prehydrolysis liquor of Kraft based processes, or the spent liquor of the neutral sulfite semichemical processes, are also discussed. Although these techniques seem to be industrially attractive, the purity of lignin that is produced in these processes are not high.
Kameshwar, A. K. S., & Qin, W. (2016). Lignin Degrading Fungal Enzymes (pp. 81–130). https://doi.org/10.1007/978-981-10-1965-4_4