Evaluation of the wastewater generated during alkaline pretreatment of biomass for feasibility of recycling and reusing

Abstract

We evaluated the wastewater generated in the alkali pretreatment process of Miscanthus sacchariflorus with sodium hydroxide for the feasibility of recycling and reusing. After thermal alkali pretreatment of the biomass, the separated alkaline solution and the biomass wash water were filtrated using several different types of membranes to recover sodium hydroxide, as well as to eliminate lignin-hemicellulose fractions from the wastewater. Ion concentration, total organic carbon, and acid-hydrolyzed carbohydrate contents were analyzed to evaluate the quality of the alkaline wastewater. The data indicated that a poly(ether)sulfone-based ultrafiltration (UF) membrane filter with a low molecular weight cut-off was able to recover > 98% sodium ions and to remove > 60% of solubilized organic carbon fractions from the alkaline wastewater. These results indicated that filtration using UF membrane could be an alternative strategy to reuse wastewater and to recover the alkali catalyst in the alkali pretreatment process.