Development of a continuous fixed-bed column to eliminate cadmium(II) ions by starch-g-poly(acrylic acid)/cellulose nanofiber bio-nanocomposite hydrogel.

Abstract

This paper presents an experimental study on continuous adsorptive removal of Cd2+ from the water body using a bio-nanocomposite hydrogel within a fixed-bed column (FBC) system. The bio-nanocomposite hydrogel was synthesized based on starch grafted poly(acrylic acid) (St-g-PAA) reinforced by cellulose nanofibers (CNFs). The effects of processing conditions including pH, flow rate, and initial concentration of Cd2+ on adsorption efficiency were examined. Based on the results, the highest removal efficiency was achieved to be 82.5% at pH of 5, initial concentration of 10 mg L-1, and flow rate of 5 mL min-1. Furthermore, by applying isotherm models, it was uncovered that the Langmuir isotherm model was the most appropriate one, and the maximum adsorption capacity was 40.65 mg g-1. Also, an adsorption process was carried out using the FBC system, and the outcome data were processed using Thomas and Yoon-Nelson models to find the characteristics of the column. In this study, the recovering capacity of the exhausted hydrogel was evaluated. Desorption process efficiencies of batch and continuous operations were obtained to be 91.9% and 90%, respectively.