Adsorption of La3+ and Dy3+ ions on biohydroxyapatite obtained from pork bones gasified with steam

Adsorption of La³⁺ and Dy³⁺ from their aqueous nitrate solutions on biohydroxyapatite (BHAP) originally prepared from raw pork bones by steam gasification of has been investigated for the La³⁺and Dy³⁺ concentrations within the range of 1.44·10^–4–8.06·10^–3 mol/dm³ and 2.71·10^–5 5.68·10^–3 mol/dm³, respectively. It was found that saturation of the lanthanide uptake occurred at 0.0625 moles of Ln³⁺ per mole of BHAP. Two model isotherms, i.e., Langmuir (q_e = qmCe/((1/K_L) + C^e)) and Freundlich (logqe = logK_F + (1/n)logCe), were used to fit the adsorption data. The following isotherm parameters were found for La³⁺: q_m = 0.1265 mol/kg, K_L = 2701 dm³/mol, n = 5.61, K_F = 0.283 (mol/kg)·(dm³/mol)1/n and for Dy³⁺: q_m = 0.1223 mol/kg, KL = 3635 dm³/mol, n = 5.82, KF = 0.306(mol/kg)·(dm³/mol)1/n. A better correlation was found for the Freundlich model. A relatively high value of the n parameter in the Freundlich equation suggests heterogeneous chemisorption of lanthanide ions.