New carbon fibre adsorbents based on natural cellulose

Abstract

The expansion of the areas of application of carbon fibre materials (CFM) made it necessary to create new varieties with a number of valuable properties [1][2][3][4][5][6][7][8]. These properties of CFM allow using them in different areas of modern technology and in some cases, forr example, in creating construction materials, severe requirements are imposed on the physicomechanical indexes, while in other cases, the strength is not of decisive importance, but the adsorption [5][6][7][8], ion-exchange [9], or catalytic properties [10] are the most important. It is preferable to use less expensive CFM for manufacturing new CFM, so-called sorption-active materials (SCFM) [4,5]. However, there has recently been a trend toward sharply rising prices and a shortage of primary stock. The importance of using secondary resources of some textile products, for example, wastes from the flaxprocessing industry, has increased for this reason. In our opinion, the use of secondary stock (tow) from the flax-processing industry for manufacture of SCFM can be 2-3 times more efficient than using hydrated cellulose or polyacrylonitrile fibre materials. In addition, the study of thermal transformations of natural cellulose fibres is of both theoretical and applied importance, since it predetermines the possibility of regulating the processes of their thermooxidation.It should be noted that the effect of chemicaI reagents on pyrolysis of natural cellulose, wood in particular, has been the subject of many studies whose results are most completely summarized in [11][12][13][14]. As these studies showed, chemical reagents alter the temperature region of active pyrolysis of wood or polymer fibres, accelerate the process at lower temperatures, and change the activation energy of thermal reactions. The degree of the effect of the reagents is most frequently determined by the nature and to a lesser degree, the concentration of the additives.However, the effect of reagents in pyrolysis of natural cellulose is not limited to their effect on the parameters of pyrolysis alone. The quantitative and sometimes also the qualitative composition of the final product changes most frequently in carbonization of cellulose in the presence of inorganic, usually phnsphorus-containing additives [14]. The density and degree of order of the carbon matrix of the fibre simultaneously increases and its reactivity in subsequent treatments decreases [14,15].In the study examined below, carbonization and subsequent activation of natural cellulose fibre stock, in particular flax tow, were investigated by derivatographic, structural-sorption, and adsorption methods.Flax cloth (sarp cloth), nonwoven needle-punching material (NM), and flax sewing thread (GOST 11970.2-76) were used as the initial stock and NaH2PO 4, KH2PO4, and K2HPO 4 were selected as the inorganic additives. The criteria for selection of the phosphorus-containing additives were not only their effectiveness and availability, but also the technological effectiveness of their use for manufacturing CFM and ...