Precipitation of Lignosulphonates from Sporl Liquid by Calcium Hydroxide Treatment

Precipitation of lignosulphonates from the liquor for sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) by addition of Ca(OH)2 was investigated in this work. The experiment was conducted in a reaction temperature range of 20 to 75C for 90 minutes with Ca(OH)2 charge varying from 20 to 90 g/L and a range of liquid enrichment ratio of 1 to 5. It was found that increased Ca(OH)2 charge, duration time, reaction temperature, and liquor concentration each tended to improve lignosulphonates precipitation, but tended to hurt fermentable sugars conservation. Application of Ca(OH)2 20 g/L to SPORL liquid without enrichment at 30C for 90 minutes could be an optimal condition. Under this condition, 25.95% of the lignosulphonates was precipitated for further utilization, while calculated amounts of 106.46% of glucose and 60.25% of xylose were conserved for further fermentation.