Regenerated Cellulose Fiber Functionalization by Two-step Oxidation Using Sodium Periodate and Sodium Chlorite - Impact on the Structure and Sorption Properties

Abstract

Successful conversion of cellulose hydroxyl (OH) to carboxyl (COOH) groups is the goal of many modification procedures since COOH groups enhance the polarity of the fibers' surface and can be used for further fibers' functionalization. In this work, in order to obtain 2,3-dicarboxycellulose, the regenerated cellulose fibers (viscose) in the form of fabric were functionalized through two-step oxidation: with NaIO4 to introduce CHO groups followed by NaClO2 for CHO conversion to COOH groups. After oxidations, the fibers' morphology, surface chemistry, crystallinity, and surface charge were investigated using scanning electron microscopy (SEM), Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction analysis (XRD), and zeta potential measurements, respectively, as well as content of COOH groups determined by volumetric titrations. Sorption properties, i.e. moisture sorption, water retention power, and sorption of silver ions (Ag+) were evaluated and correlated with oxidation parameters. The interaction with model ion - Ag+ revealed that COOH groups, when maximum content obtained in oxidized fibers was 0.27 mmol center dot g(-1), were available for binding Ag+ in nearly 1:1 ratio. The proposed oxidative protocol represents an effective method for COOH groups' introduction into regenerated cellulose fibers, improvement of fibers' sorption properties without deterioration of their crystallinity, and opens up a possibility for further functionalization of 2,3-dicarboxycellulose.