Influence of Lignin Characteristics on the Productivity of Ultrafiltration Membranes

Membrane fouling is one of the major obstacles to its implementation in the black liquor industry. Ultrafiltration having the ability to concentrate and fractionate the lignin product for renewable energy and chemical product from renewable substance like hard or soft wood and agricultural residues as alternative potential for bioretinery. The drawback of ultrafi ltration application in biorefinery is the requirement to handle the complex material which consists of cellulose, hemicellulose and lignin. Plus minor components like proteins, extractives and minerals. In our experiments an alkaline sodium hydroxide based process has been used for the decomposition of wheat straw. The derived solution contained mainly lignin and acetate as well some of the C5 and C6 sugars as monomers or oligomers. The main aim of this work to evaluate the influence of lignin characteristics during the separation from the alkaline sol ution on the membrane performance, ultra filtration membrane materials with molecular weight cut off (MWCO) of 3KD had been used, while permeate and the concentrate had been analyzed for molar mass and lignin concentration, to evaluate the influence of lignin characteristics on the membranes, and to find a trend line between the production capacity and quality of the final lignin product. The filtered solution having lignin concentration around 0.84 mg/ml, while the pH was around 10.6, after concentrating 20, 40, 60 and 80 % of the initi al volume, the membranes rejection capacity for
lignin was around 85.53, 81.64, 73.84 and 58.36 % for the concentrate volumes, while the molecular weight of the concentrate lignin was 3900, 3950, 4000 and 4500 Dalton. The concentrate lignin had reduced the membrane Flux in the following order I 5.49, 18. 12, 28.28 and 50.04 % for each concentration.