Fractionation of Lignin Streams Using Tangential Flow Filtration

Lignin fractionation helps its valorization processand yields high-quality and -value products. In this study, cascadingtangentialflowfiltration (TFF) was employed for the fractionationof lignin molecules. The lignin-rich stream was obtained from thepretreatment process of corn stover using alkali (NaOH) andcholinium lysinate ([Ch][Lys]) as the catalyst. The effect of TFF(microfiltration, ultrafiltration, and nanofiltration) on ligninmolecular weight, sugar distribution, viscosity, and lignin functionalgroups was investigated. In general, the study concluded that theaverage molecular weight (MW) and polydispersity of thepermeate stream decreased with the reduction of the membranepore size. TFF was effective in separating the low-MW lignin(200-350 Da) from the aqueous stream. Approximately 2% of monomeric lignin and 10-20% of low-molecular-weight lignin wererecovered from NaOH- and [Ch][Lys]-extracted streams. Techno-economic analysis (TEA) results show that a high percentage ofthe low-MW lignin extraction can be achieved via a cascade TFF membrane operating at high transmembrane pressures (TMPs) andcross membrane velocities. Additionally, a high initial concentration of lignin in the liquid stream plays a critical role in the ligninproduct yield and recovery cost

Automated summary

Fractionation of lignin using TFF was studied, and the effects of different membrane pore sizes on lignin molecular weight, sugar distribution, viscosity, and lignin functional groups were investigated. The results showed that TFF could effectively separate low-molecular-weight lignin from the aqueous stream.