Nanofiltration of spent sulphite liquor model solutions with a focus on the role of lignosulfonates
Sprache des Vortragstitels:
PERMEA 2019 - Membrane Conference of Visegrad Countries
Sprache des Tagungstitel:
The sulphite pulping process is a common alternative to the Kraft pulping process. Different types of wood can be treated to give pulp for the paper and cellulose fibre industry. The pulping process separates the cellulose from the hemicelluloses, lignin and other wood components. Except for the cellulose, all compounds including the cooking chemicals are dissolved in the so-called spent sulphite liquor (SSL). Usually, SSL is combusted and thereby the cooking chemicals are recovered. In terms of an integrated biorefinery process, at least a partial substantial use of SSL components is desired.A promising way is the use of sugars from the SSL in a fermentation process to produce platform chemicals. Therefore, membrane filtration can be applied to separate the sugars from the lignosulfonates (LS) and other wood degradation products like acetic acid, furfural and hydroxymethylfurfural (HMF), which are known as fermentation inhibitors.First, different nanofiltration membranes were studied with a LS free model solution containing a mixture of glucose, xylose, gluconic acid, acetic acid, HMF and magnesium sulphate. The effects of different pH values, total organic contents, temperatures and pressures on the separation performance were under investigation.Regarding the separation selectivity between sugars and inhibitors and the overall permeate flux the NF270 membrane from Filmtec showed to be the most promising membrane. To sum up, it is shown, that nanofiltration can be applied to reduce inhibitor from wood derived SSL upstream the fermentative production of platform chemicals. However, further investigations still need to be done to evaluate the best compromise between inhibitor removals and achievable permeate flux. Additionally, the not completely explainable fact of negative retention of HMF and acetic acid need to be studied also more in detail.