Lignin Recovery Using Alkaline Pretreatment of Walnut Shells

The effects of alkaline pretreatment of walnut shells (WS) utilizing NaOH, Ca(OH)(2), or KOH were studied. The highest lignin recovery was obtained from WS pretreated with NaOH-glycerol. The optimum lignin recovery after pretreatment could be achieved when the NaOH/solid value was 20:1 (mL g(-1)). CaCl2 loading could enhance lignin flocculation, which improved the lignin recovery. Also, the efficiency of enzymatic hydrolysis was determined when xylanase and cellulase were added to the pretreated residue. WS pretreated in NaOH-water and NaOH-glycerol solutions were found to result in the highest xylose and glucose concentrations. This study indicates the broad application prospects of alkaline pretreatment of lignocellulosic biomass in agriculture and industry.