Fabrication of nanocellulose-graphene oxide-polyvinyl alcohol aerogel under ambient conditions for methylene blue removal

Abstract

This study investigates the synthesis of aerogels based on cellulose nanofibers (CNF) reinforced with graphene oxide (GO) and polyvinyl alcohol (PVA) via a simple solvent exchange and ambient drying method. Cellulose nanofibers were extracted from a stem of the nipa palm tree through mechanical and chemical treatments, exhibiting a crystallinity index of approximately 69% and a crystallite size of about 2.01 nm. Three types of aerogels were prepared through solvent exchange processes using acetone, ethanol, and isopropyl alcohol under ambient conditions, resulting in densities of 0.025 ± 0.002 g/cm³, 0.023 ± 0.001 g/cm³, and 0.024 ± 0.003 g/cm³, respectively, and high porosities of 98.350 ± 0.129%, 98.538 ± 0.057%, and 98.436 ± 0.193%. The porous structure and interactions between components within the aerogels were characterized using optical microscopy (OM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis. Additionally, the properties and methylene blue (MB) dye removal performance of the aerogels were investigated. Thermal properties were evaluated using thermogravimetric analysis (TGA), mechanical properties were determined by compression tests, and the MB adsorption capacities of aerogels exchanged with acetone, ethanol, and isopropyl alcohol were found to be 99.52%, 99.77%, and 99.49%, respectively, as determined by UV-Vis spectroscopy. The reusability of the aerogels after five adsorption-desorption cycles was 99.00%, 99.11%, and 99.07%, respectively. The pseudo-second-order kinetic model was suitable for describing the adsorption process of MB onto CGP-Et and CGP-Iso aerogels, while the pseudo-first-order kinetic model was more appropriate for the CGP-Ac aerogel. This study demonstrates the potential of a simple and efficient fabrication process for producing a green adsorbent for the removal of methylene blue dye from contaminated water.