title: Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption.
abstract: A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m(2)/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available.
authors.affiliation: Aalto University School of Chemical Technology, Department of Biotechnology and Chemical Technology, Espoo, Finland. Electronic address: mika.sipponen@aalto.fi.
authors.forename: Mika Henrikki
authors.initials: MH
authors.lastname: Sipponen
authors.affiliation: Aalto University School of Chemical Technology, Department of Biotechnology and Chemical Technology, Espoo, Finland.
authors.forename: Ville
authors.initials: V
authors.lastname: Pihlajaniemi
authors.affiliation: Aalto University School of Chemical Technology, Department of Biotechnology and Chemical Technology, Espoo, Finland.
authors.forename: Kuisma
authors.initials: K
authors.lastname: Littunen
authors.affiliation: Aalto University School of Chemical Technology, Department of Biotechnology and Chemical Technology, Espoo, Finland.
authors.forename: Ossi
authors.initials: O
authors.lastname: Pastinen
authors.affiliation: Aalto University School of Chemical Technology, Department of Biotechnology and Chemical Technology, Espoo, Finland.
authors.forename: Simo
authors.initials: S
authors.lastname: Laakso
mesh_terms: D000143:Acids / Q000737:chemistry*; D000327:Adsorption; D018554:Avena / Q000737:chemistry; D001399:Azure Stains / Q000737:chemistry; D002412:Cations; D002482:Cellulose / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008031:Lignin / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D031786:Saccharum / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014908:Triticum / Q000737:chemistry
chemical_list: D000143:Acids; D001399:Azure Stains; D002412:Cations; D004396:Coloring Agents; C036909:lignocellulose; D017665:Hydroxyl Radical; C025819:Azure B; D002482:Cellulose; D008031:Lignin; C027433:bagasse
keywords: Acidic; Adsorption; Hydroxyl; Lignin; Surface area