Selective removal of Pb²⁺ by AlPO₄

Abstract

Aluminium(III) phosphate was observed to have a very high selectivity towards Pb²⁺ ions. Under similar conditions, the sorption capacities of the exchanger were observed to follow the order: Pb²⁺ > Zn²⁺> Ni²⁺ > Co²⁺. The potentiometric titration data were used to determine the deprotonation constants (pKa) of AlPO₄ which were dependent upon the temperature and nature of the metal cations present in the aqueous phase. Different physico‐chemical methods i.e. FTIR, EPM and the wet chemical analyses were used to investigate the uptake mechanism of Pb²⁺ by the solid, which showed that no new solid phases were present in the solid residue after sorption of Pb²⁺ at pH 5. The exchange between protons from the surface and Pb²⁺ from solutions was found to be responsible for Pb²⁺sorption by aluminum(III) phosphate.

Keywords:

• Sorption
• ion exchange
• metal ions
• metal phosphates
• potentiometric titration