Cadmium removal from aqueous medium by jute stick activated carbon using response surface methodology: factor optimisation, equilibrium, and regeneration

Abstract

ABSTRACT Heavy metal contamination of water is a burning global issue, and enormous importance has been given on easily applicable watertreatment methods namely adsorption. However, search for an efficient and reusable adsorbent is ever-evolving. In this study, activated carbon from highly ligno-cellulosic jute stick (JS-AC), the agricultural by-product of jute (Corchorus olitorius), was evaluated as a new adsorbent for removing cadmium (Cd) from the aqueous medium. The direct and interaction effects of four independent adsorption factors namely, initial Cd(II) concentration (20–100 mg/L), adsorbent dose (0.5–1 g/L), solution pH (3–7), and time (30–180 min) were investigated by applying response surface methodology (RSM). A 24 Box-Behnken matrix model with 3 centre points indicated that the maximum % Cd(II) removal was achieved at the initial concentration, dose, pH and time of 60.87 mg/L, 0.5 g/L, 7, and 30 min, respectively. The adsorption equilibrium was investigated by applying Freundlich, Langmuir, Temkin, and Jovanoic isotherm models while Langmuir isotherm exhibited the best fit (R2 = 0.99). The maximum Cd(II) adsorption capacity value of JS-AC was 73.53 mg/g. Finally, JS-AC was regenerated with 0.1M HNO3 as the desorption medium and reused for five successive cycles. This study indicated that jute stick, the under-utilised agro-residue of a cash crop, could be converted into a valuable product like JS-AC which offers immense application potential as an efficient and reusable adsorbent to treat Cd(II) contaminated aqueous medium before releasing in the environment.