Hemicellulose Fouling Behaviour during Nanofiltration of Press Liquor

Nanofiltration of press liquor from viscose-type textile fibre production was investigated using a laboratory-scale cross-flow test apparatus. Feed solutions
contained about 200 g/l sodium hydroxide and a high concentration of hemicellulose as a contaminant originating from the raw material wood. The effect of various pretreatments and the addition of reagents affecting the solution state of hemicellulose on flux, retention and irreversible fouling was studied. Turbidity measurements were used to track the evolution of hemicellulose aggregates. Aggregation generally coincided with distinct flux decline during nanofiltration thus indicating that this phenomenon may result in the build-up of gel layers at the membrane surface. Partial neutralisation with sulfuric acid caused extremely severe fouling, whereas methanol addition had a minor effect. The impact of heat treatment and oxidative degradation of hemicellulose on
nanofiltration performance was attributed to changes in molecular mass distribution.