Utilization of Nanocrystalline Cellulose for Adsorption of Divalent Cobalt Ions in the Aqueous Phase

Abstract

Nanocrystalline cellulose (NC) is a cellulose derivative product that has attracted a lot of attention because of its versatile applications, one of which is in adsorption. In this study, NC was prepared through H₂SO₄-hydrolysis of filter paper. Several physical characterizations were employed to confirm the formation of the NC nanoparticles, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and Fourier transform infrared spectroscopy (FTIR). The nano-rod-shaped NC particles, with an average particle length of 255 nm, were observed from the electron micrographs. The resemblance characteristic of NC with cellulose was demonstrated from the occurrence of XRD peaks at (110) and (200) lattice plane. The FTIR bands’ spectra of the NC are similar to that of the reported literature. The NC was utilized as the adsorbent for the removal of cobalt ions in the synthetic solution. The effect of pH on the removal of cobalt ions by NC was evaluated by employing potentiometric titration. It was revealed that the complexation between the two compounds occurs greater at a pH of 6.6. The adsorption isotherm of cobalt ions was investigated at three different temperatures of 30, 45, and 60°C. The adsorption isotherm was found to be well fitted with the Langmuir model, with the maximum adsorption capacity of 47.53 mg g^-1 at 30°C. The adsorption capacity was found to decline as the temperature increased, where the maximum adsorption capacity was 44.62 ± 2.32 and 40.56 ± 2.03 mg g^-1 at 45 and 60°C, respectively. The adsorption of cobalt ions on NC shows the exothermic adsorption behavior.