The Effect of Milling and Alkali Treatments on the Accessibility of the Lignins ofPinus radiataandEucalyptus regnans

Abstract

Keywords Ball milling Lignin accessibility Lignin-carbohydrate linkage Pinus radiata Eucalyptus regnans Schlüsselwörter (Sachgebiete) Schwingmahlung Zuganglichkeit von Lignin Lignin-KohlenhydratBindung The Effect of Milling and Alkali Treatments on the Accessibility of the Lignins of Pinus radiata and Eucalyptus regnans SummaryVibratory ball milling of wood meal produced a large increase in the amount of lignin soluble in cold (20° C) . aqueous sodium hydroxide. This effect was greater for Pinus radiata than for Eucalyptus regnans. These results indicate a mechanical liberation of lignin by the milling and/or cleavage of alkali-sensitive bonds. The yield of milled wood lignin from alkali-treated milled wood of E. regnans was equal to the amount of lignin soluble in cold alkali but was much less from P. radiata apparently because of solubility limitations. Hot (95° C) alkali treatment of milled wood led to a higher amount of alkali soluble lignin and a lower yield of milled wood lignin for both species. About half of the lignin appears to be bound to carbohydrate by bonds resistant to alkali at 20° C. Die Wirkung der Mahlung und Alkali-Behandlung auf die Zugänglichkeit des Lignins von Pinus radiata und Eucalyptus regnans Zusammenfassung Durch Behandlung von Holzmehl in einer Schwingmühle nahm die Menge an Lignin, das in kalter (20° C), wäßriger 0,1 M Natronlauge löslich war, stark zu. Die Wirkung war bei Pinus radiata größer als bei Eucalyptus regnans. Diese Befunde ergaben sich infolge mechanischer Freisetzung von Lignin durch den Mahlvorgang und/oder durch Lösung der alkali-empfindlichen Bindungen. Die Ausbeute an milled wood Lignin aus mit Lauge behandeltem gemahlenem Holz von E. regnans war ebenso groß wie an Lignin, das in kalter Lauge löslich war, aber deutlich geringer bei P. radiata, wahrscheinlich wegen begrenzter Löslichkeit. Wurde gemahlenes Holz mit heißer Lauge (95° C) behandelt, so ergab sich ein höherer Betrag an alkali-löslichem Lignin und eine geringere Ausbeute an milled wood Lignin für beide Holzarten. Etwa die Hälfte des Lignins scheint an Kohlenhydrate durch Bindungen geknüpft zu sein, die Lauge von 20° C widerstehen. IntroductionIsolation of milled wood lignin from Eucalyptus regnans wood was shown by Bland and Menshun (1967) to be assisted by mild alkali pretreatment of the wood before milling. It was suggested that this treatment liberated lignin because it was attached by alkali-sensitive bonds to the polysaccharides. Brownell (1971) has found that while treatment of spruce wood by alkali before milling leads to a higher yield of lignin which is soluble in benzyl alcohol-dimethylformamide, post-treatment of milled wood by alkali gives no enhancement of yield. From this he suggested that the main effect of the alkali pretreatment was that it facilitated grinding by embrittlement of the wood, rather than by bond cleavage. We have observed that alkali pretreated milled wood tends to be more free flowing than untreated and that the mill balls remained bright and clean with no adhering wood pow...

Surface Changes on Acetylation and Exposure to Ultraviolet Radiation of Pinus radiata Using X-Ray Photo-Electron Spectroscopy

“…Milled wood lignin (MWL) was prepared from Pinus radiata sapwood by the standard Bjorkman method (Bjorkman 1956), except that an 80 : 20 acetone/water solution was used for lignin extraction (Bland and Menshun 1973). The MWL was acetylated by reacting it with acetic anhydride for 2 hours at 120°C.…”

Effect of mild torrefaction on pulverization of Norway spruce (Picea abies) by oscillatory ball milling: particle morphology and cellulose crystallinity

“…Vibration mills cause a drastic decrease in cellulose crystallinity in the particles (Schwanninger et al 2004;Kobayashi et al 2007Kobayashi et al , 2008Agarwal et al 2013;Karinkanta et al 2013a). This kind of milling enhances the reaction rate of wood hydrolysis (Pew and Weyna 1962;Millett et al 1976Millett et al , 1979 and facilitates mild lignin isolation by solution (Sarkanen and Ludwig 1971;Bland and Menshun 1973;Maurer and Fengel 1992;Guerra et al 2006;Li et al 2011;Qu et al 2012). It is also known that different ball mills (such as planetary and tumbling ball mills) destruct heavily the fibrous structure of wood (Fukuzawa et al 1982;Mikushina et al 2003) and cause a drastic decrease in the cellulose crystallinity (Gharpuray et al 1983;Rivers and Emert 1987;Stubičar et al 1998;Da Silva et al 2010).…”