Suchergebnisse

A method for the selective extraction of hemicellulose from wheat straw involving cold alkaline extraction and subsequent separation by precipitation with ethanol is proposed. Wheat straw affords selective separation of the hemicellulose fraction from the cellulose and lignin fractions with the proposed method. The hemicellulose yield was optimized by using a 2n factor design to examine the influence of temperatures (temperature was designed between 20 and 40 ◦C), operation times (operation time was designed between 30 and 60 min) and alkali concentrations (alkali concentration was designed between 80 and 120 g L−1). These conditions allowed 56.1% of all hemicellulose initially present in the raw material, and 59.1% of the lignin, to be extracted. Subsequent separation of hemicellulose in the liquid phase from the cold alkaline extraction by precipitation with ethanol provided a fraction containing 39.4% of all hemicellulose (45.2% hemicellulose in extract/total extract) and only 12% of all lignin in the raw material. ; The authors are grateful for the FPU grant from the Spanish Ministry of Education. Also they thank to Spanish Ministry of Economy and Competitiveness (former Ministry of Science and Innovation) contracts. The authors acknowledge financial support for this investigation has been provided by CDTI (CENIT-E-CDTI-BioSos-CEN-2009-1040) and supported by Ministry of Economy and Competitiveness, "Local Investment fund for employment". Government of Spain, Junta de Andalucia, CICYT-FEDER (Science and Technology Inter Ministerial Commission, Spanish Government - European Regional Development Fund), project number AGL2009-13113 and the business group ACCIONA INFRAESTRUCTURAS, S.A.