Sorption properties of an amorphous hydroxo titanate towards Pb²⁺, Ni²⁺, and Cu²⁺ ions in aqueous solution

ABSTRACT

Titanates may be selectively used as inorganic adsorbents for heavy metal ions owing to their stability and fast adsorption kinetics. Nevertheless, the synthesis of such materials usually requires extreme reaction conditions. In this work, a new titanium-based material was rapidly synthesized under mild laboratory conditions. The obtained amorphous hydroxo titanate was tested for heavy metal sorption through kinetic and equilibrium batch tests, which indicated that the new material had high adsorption rates and adsorption capacities towards Cu²⁺, Ni²⁺ and Pb² ions. Adsorption kinetics were pseudo-second order, and equilibrium data fitted the Langmuir isotherm model. The calculated maximum adsorption capacities of Cu²⁺, Ni²⁺ and Pb²⁺ in deionized water were around 1 mmol g⁻¹, and they decreased for Cu²⁺ and Ni²⁺ in the presence of Na⁺, Ca²⁺ and Mg²⁺ ions, whereas the alkali metal ions did not influence Pb²⁺ uptake. The efficiency of adsorption and recovery of lead ions were evaluated through column dynamic tests, by feeding the column with groundwater and tap water spiked with Pb²⁺. The high performance of the hydroxo titanate over several cycles of retention and elution suggested that the product is potentially useful for the solid phase extraction of lead at trace levels in natural water samples, with potential use in metal pre-concentration for analytical applications.

KEYWORDS:

• heavy metals
• hydroxo titanate
• peroxymonosulfate
• preconcentration
• sorption

Acknowledgments

Mr. Giuseppe Bagnuolo and Mr. Giovanni Berardi are gratefully acknowledged for the assistance provided in analytical work.