Effect of surface chemistry and content of nanocrystalline cellulose on removal of methylene blue from wastewater by poly(acrylic acid)/nanocrystalline cellulose nanocomposite hydrogels

Nanocrystalline cellulose (NCC) was modified with (3-aminopropyl)triethoxysilane (APTES) and hexadecyltrimethoxysilane (HDTMS) to obtain NCC-APTES and NCC-HDTMS respectively. The modification was confirmed by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) spectroscopy, thermogravimetric analyses (TGA), dynamic light scattering and zeta potential analyses. A series of poly(acrylic acid) (PAA)/NCC, PAA/NCC-APTES, and PAA/NCC-HDTMS hydrogel nanocomposites with various amounts of nanoparticles were synthesized by in situ radical polymerization method. Nanocomposites were characterized using XRD, TGA and field emission scanning electron microscopy. Also, swelling behavior of hydrogel nanocomposites showed that NCC and NCC-APTES helped swelling of hydrogels whereas CNN-HDTMS decreased swelling ratio. The hydrogel nanocomposites were also used as adsorbents for removal of methylene Blue from aqueous solution at different pH values. Results showed that the adsorption capacity for dye increased with increasing pH and contact time. Introducing NCC into hydrogel nanocomposite network affected adsorption capacity. Finally, adsorption kinetics was studied by three kinetic models including pseudo-first-order, pseudo-second-order and intra-particle diffusion models.