Investigation the correlation between chemical structure and swelling, thermal and flocculation properties of carboxymethylcellulose hydrogels

Abstract Hydrophilic polymer networks (hydrogels) based on sodium carboxymethylcellulose (NaCMC) and polycarboxylic acids (oxalic, succinic, citric and adipic) as cross‐linking agents are synthesized by esterification reaction; one series of NaCMC hydrogels cross‐linked with citric acid is prepared with acrylamide and acrylic acid (Aam/Aac) copolymers using the design of semi‐interpenetrating polymer networks (semi‐IPN), in order to increase their potential application for flocculation purposes. The Infrared spectroscopy (FTIR) of hydrogels confirms the esterification reaction between NaCMC and cross‐linking agents. Results of swelling measurements show that citric acid in the amount of 15 wt% gives the hydrogels with the best absorption capacity. The results of Differential scanning calorimetry (DSC) and Thermal gravimetric analysis (TGA) show no significant difference in thermal properties of neat and semi‐interpenetrating NaCMC hydrogels. The amorphous nature of hydrogels is confirmed by X‐ray diffraction analysis (XRD). The results of flocculation study show that combination of NaCMC network and Aam/Aac copolymer with initial mass ratio of 10/90 creates a theoretical platform for the production of flocculant which could show high efficacy in purifying of water dominated by positively charged particles.