Potential of nano crystalline calcium hydroxyapatite for Tin(II) removal from aqueous solutions: Equilibria and kinetic processes

Abstract

The potential of the synthesized nano hydroxyapatite to remove Sn2+ from aqueous solutions was investigated in a batch reactor under different experimental conditions. The study also investigates the effects of process parameters such as initial concentration of Sn2+ ions, temperature, and adsorbent mass. Various thermodynamic parameters, such as ΔGo, ΔHo and ΔSo have been calculated. The thermodynamics of an Sn2+ ion onto nano HAp system indicates a spontaneous and endothermic nature of the process. Tin uptake was quantitatively evaluated using the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich models. The adsorption data follow the adsorption equilibrium described well by the Langmuir isotherm model with maximum adsorption capacity of 2500 mg/g of Sn2+ ions on nano HAp. Using the second-order kinetic constants, the activation energy of adsorption (Ea) was determined as 4.125 kJ mol−1 according to the Arrhenius equation.

Keywords

• Adsorption
• Nano crystalline hydroxyapatite
• Sn2+ ion
• Isotherms
• Thermodynamics
• Kinetic