Precipitation of lignosulphonates from sporl liquid by calcium hydroxide treatment

Abstract

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 75°C 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 30oC 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.