13-08: Parameter effects on straw lignin recovery from alkali liquors

Monday, April 29, 2013
Exhibit Hall
Tiraporn Junyusen, Lisbeth M. Goddik and Michael H. Penner, Food Science and Technology, Oregon State University, Corvallis, OR
An approach to enhancing the reactivity of lignocellulosic materials is component fractionation through low severity alkaline-aqueous treatments. During such treatments nearly all of cellulose component of the feedstock remains in the solid phase while a significant portion of the hemicellulose and lignin are transferred to the liquid phase. The focus of the present study is recovery of lignin via precipitation from the post-treatment alkaline aqueous liquor (PTAAL). Lignin recovery is important due to lignin’s potential for subsequent value-added processing. In this work, wheat straw was treated with 5% NaOH at 50°C for 5 h to produce PTAAL. Lignin recovery from PTAAL, quantified as precipitated solids, acid insoluble lignin, and acid soluble lignin, was evaluated over a range of pH (1.5 to 7), temperature (4o to 70oC), supplemental salts (0 To 2.5M) and hemicellulose content (0 to 120% original PTAAL). Lignin recovery, measured as ash-adjusted solids, generally increases as pH decreases. Removal of non-hemicellulose, neutral pH-precipitatable components reduces overall low pH lignin yields. Temperature does not appear to significantly affect rates or extents of solids recovery at low pH; at neutral pH, temperature increases rates of precipitation but seems to have minimal to no effect on extents of lignin recovery. At low pH and moderate temperature ionic strength has little effect on lignin recovery; at neutral pH and moderate temperature ionic strength significantly effects solids recovery. Hemicellulose interferes with rates of lignin precipitation and appears to co-precipitate. Structural implications of these results are considered.