Abstract
A new, environmentally cleaner, technology of obtaining microcrystalline cellulose of fibers of hemp was proposed. The various stages of obtaining microcrystalline cellulose were studied and the optimum values of technological parameters of alkali extraction of hemp fibers, organosolv pulping, chelation and hydrolysis of cellulose were defined. It was determined that the consistent treatment of fibers of hemp by extraction of 5 % KOH solution during 210 minutes at the temperature of 95 °С, performic cooking in a mixture of 85 % formic acid and 30 % of hydrogen peroxide in the ratio of 60:40 of volume % at 100 °C during 210 min, chelation by the solution of trilon B of the concentration of 10 g/l during 30 min at 50 °C and hydrolysis by a mixture of 98 % acetic acid and 30 % of hydrogen peroxide solution in the ratio of 70:30 of volume %, allows obtaining microcrystalline cellulose in the form of white powder with a degree of polymerization 80 and the content of sulfate ash of 0.10 %. Using the methods of scanning electronic microscopy, thermogravimentric analysis and Xray diffraction confirmed that the consistent multistage chemical treatment increases the content of crystalline part of cellulose by the removal of extractive and mineral substances, hemicelllulose and amorphous fraction of cellulose of the fibers of hemp. Application of the proposed technology of obtaining microcrystalline cellulose from the fibers of hemp is environmentally more friendly and enables to reduce significantly the cost of finished products by using national, annually renewable plant raw materials compared to imported cotton or pine cellulose.
Highlights
IntroductionThe number of studies of new promising materials based on natural polymers has increased significantly lately, in particular cellulose, which is related to economic and ecological necessity of replacing natural exhaustible sources of carbohydrates (oil, coal) to renewable plant raw materials
The number of studies of new promising materials based on natural polymers has increased significantly lately, in particular cellulose, which is related to economic and ecological necessity of replacing natural exhaustible sources of carbohydrates to renewable plant raw materials
In this paper we studied the hemp fibers of the 2012 crop from Chernigov Region (Ukraine), which had the following chemical composition: cellulose – 46.2 %; lignin – 17.0 %; resins, fats, waxes – 1.4 %; pentosans – 20.2 %; ash – 1.44 %; sulfate ash – 1.63 % to the weight of absolutely dry raw material (a. d. m.)
Summary
The number of studies of new promising materials based on natural polymers has increased significantly lately, in particular cellulose, which is related to economic and ecological necessity of replacing natural exhaustible sources of carbohydrates (oil, coal) to renewable plant raw materials. MCC is characterized by chemical resistance, insolubility in water and organic solvents, absence of taste, smell and color that allow using it as a filler, stabilizer and emulsifier in food processing, cosmetic and pharmaceutical industries [4]. The main raw material for obtaining microcrystalline cellulose remains high-quality cellulose produced from wood and cotton. The countries that have no available stocks of wood and cotton as the resources of fibers for obtaining MCC, can consider non-wood plant raw materials, such as bast plants, which have more homogeneous long cells, such as fibers of flax, hemp, kenaf [5]. Taking into account that a hectare of hemp produces the weight gain of 6 m3 per year, while deciduous trees do only up to 3.2 m3, the change of wood to hemp during the processing of cellulose is considered advisable economically and ecologically as well [6]
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