Transformations of the Carbohydrate Portion of Secondary Plant Raw Materials Subjected to Cavitation in Alkaline Aqueous Media
D. V. DUDKIN, A. S. ZMANOVSKAYA
Yugra State University, Khanty-Mansiysk, Russia
Keywords: гуминовые кислоты, механохимическое воздействие, полиозы, целлюлоза, щелочной гидролиз, окисление, кавитация, humic acid, mechanical action, polyoses, cellulose, alkaline hydrolysis, oxidation, cavitation
Abstract
The composition of polyoses isolated from the products of the mechanochemical treatment of plant raw materials was studied by physicochemical methods. It was demonstrated that mechanochemical action exerted on the components of the cell wall of plants led to hydrolytic decomposition of glycoside bonds of polyoses. A decrease of the polymerization degree of polyoses and the removal of the reaction products as water soluble substances is observed. Complete hydrolysis of polyoses at cavitation does not occur; polyose accumulation with the minimum polymerisation degree of 70-80 units is registered. The intensity of hydrolytic destruction at cavitation is conditioned by the strength of the base used in the process of mechanochemical action. Alongside with hydrolysis, oxidation of primary and secondary hydroxyls in structural units of polyose molecules takes place, resulting in the formation of carboxyl and carbonyl groups, respectively. It was suggested that at the stage of tribochemical impacts, the primary hydroxyl glucoside ring is primarily oxidized, leads to the transformation of individual sections of the cellulose chain to structure resembling irregular polymer of the glucuronic acid. Subsequent cavitation in aqueous alkaline solutions leads to decarboxylation, resulting in the transformation of the glucuronic fragment of oxidized cellulose is transformed into the D -xylose. Herewith, the entire molecule of oxidized cellulose turns into an irregular polymer consisting of the glucuronic acid and xylose. The intensity of oxidative destruction at cavitation is also conditioned by the strength of the base used in the mechanochemical action process. It was demonstrated that all polyoses obtained as a result of the mechanochemical action in aqueous ammonia solutions contain organically bound nitrogen. The use of stronger bases at cavitation contributes to its partial removal from the polymer structure. It can be assumed that nitrogen is present in polyoses as amine and amide groups.
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