Quantitative determination of carboxyl groups in cellulose polymers utilizing their ion exchange capacity and using a complexometric titration

Lidija Fras Zemljič, Karin Stana Kleinschek, Volker Ribitsch, Majda Sfiligoj Smole, Tatjana Kreze

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Abstract

Fibers functional groups may act as ion-exchange materials. The ion-exchange properties of cellulose fibres are mainly determined by the content of -COOH groups, so that their precise determination becomes a matter of special importance. The information on the amount and allocation of dissociable groups in fiber-forming polymers is very useful for clarifying thereaction mechanism of pre-treatment, treatment processes, and the production of textile fibers as well as to control the progress of oxidation processes. Chemical and structural modifications, which happen during manufacturing of polymer materials, cause changes in the number and distribution of the carboxyl groups [7]. In a recent study, cellulose fibers were acid hydrolyzed and oxidized (selectively as well as non-selectively) with the aim of obtaining a different content of carboxyl groups. The Methylene Blue method and the Complexometric titration, which are based on theion-exchange capacity of the cellulose, were used for determining the content of the of carboxyl groupsć content. For a detailed description of bothmethods used, see [{*}, 10, 11]. It should be pointed out that, to our knowledge, complexometric titration, which is a modified Sobue-Okubo, method has never been used for characterization of ion-exchange In order to checkthe validity of complexometric titration it was compared to the MethyleneBlue method. With the correlation of the results obtained using both methods it was possible to discover which one is more appropriate for the quantitative determination of carboxyl groups in cellulose. It was found that the content of carboxyl groups for oxidized fibers depends on the oxidation procedure. Increasing the carboxyl groupsć content is more expressible by non-selective oxidation in comparison with selective oxidation, where the oxidation mechanism is known. Using non-selective oxidation, any possible oxidation products may occur because the course of the oxidation process is unpredictable. A mixture of products oxidized to different degrees and according to different mechanisms is present. An excellent correlation betweenboth methods used for determination of -COOH groupsć content is evidentin spite of the different absolute results achieved (Fig. 5). However, complexometric titration is due to the lower systematic error and higher sensitivity more appropriate for determination of the carboxyl groupsć contentthan the Methylene Blue method. The Methylene Blue method is recommended as a comparison method to confirm a tendency of results obtained by complexometric titration. The results of this investigation make it quite clear that complexometric titration, used for a first time in the field of textile chemistry, is an excellent tool for monitoring the influence of oxidation on the carboxyl groups content.
Original languageEnglish
JournalMaterials Research Innovations
Volume8
Issue number3
Publication statusPublished - 2004
Externally publishedYes

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