Effects of nanocellulose on sodium alginate/polyacrylamide hydrogel: Mechanical properties and adsorption-desorption capacities

In this study, interpenetrating polymer network (IPN)-structured hydrogels were fabricated through the cross-linking of neutral polyacrylamide (PAM, the first flexible network) and the polyelectrolyte sodium alginate (SA, the second rigid network). Three types of nanocellulose, including cellulose nanocrystals (CNCs), bacterial cellulose fibers (BCs) and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-oxidized cellulose nanofibers (TOCNs), were well-dispersed in the SA-PAM gel matrix. The hydrogels, obtained with a high water content (similar to 83%), exhibit a macroporous structure with a mean pore size of 60 +/- 51 mu m and high transparency. Comparative studies indicate that BCs are more effective for enhancing the hydrogels due to their higher aspect ratio, and the compressive strength of SA-PAM-BC hydrogel is 6.59 times higher than that of neat SA-PAM. Meanwhile, TOCNs are the best fillers for improving the adsorption capacity owing to the presence of a carboxyl group, and the adsorption capacity of SA-PAM-TOCN is more than 1.3-fold that in SA-PAM. Prepared hydrogels with high mechanical strength and adsorption capacity are advantageous for their applications in wastewater treatments.