Adsorption of Ni(II) on alkali treated pineapple residue (Ananas comosus L.): Batch and column studies

Abstract

The novel alkali-treated pineapple residue was utilized for sequestration of Ni(II) ions from aqueous solution. On treatment with Sodium hydroxide the metal binding sites (free O−) of pineapple residue enhanced. Lignin and hemi-cellulose being substantial components in pineapple played a vital role in nickel adsorption. The prime functional groups present in ATPR that participated in nickel adsorption were hydroxyl and carbonyl groups, affirmed by the FTIR analysis. In a batch system maximum adsorption capacity (4.51 mgg−1) was obtained at solution pH 4–6, in 60min at 30°C. The increase in adsorption capacity from 0.95 to 7.72mgg−1 with increase in concentration from 10 to 100mgL−1 confirmed the dependence of adsorption on metal ion concentration. The equilibrium data was analyzed by Langmuir, Freundlich and temkin isotherm models and was found to be best followed by Langmuir and Freundlich isotherm models at 50⁰C. The maximum adsorption capacity (qmax) from Langmuir isotherm model was found to be 17.56mgg−1. Kinetic data analysis revealed that pseudo-second order kinetic model was best obeyed, implying that chemisorption was the rate determining step. Thermodynamic parameters (∆G°, ∆H⁰, ∆S⁰) exhibited feasible, endothermic and spontaneous nature of adsorption. The breakthrough and desorption studies were conducted by column operation and corresponding breakthrough and exhaustive capacities were found to be 20 and 50mgg−1 respectively.