Nano-calcium titanate powder was successfully prepared by a citric acid complex sol-gel method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectrophotometry (FTIR). Its adsorption capabilities for lead ion and cadmium ion were investigated. Taking the cadmium ion as an example, the thermodynamics and kinetics of the adsorption were completely studied. The results showed that the calcium titanate was perovskite nanometer powder. The particle diameter relied on the burning temperature, which became larger at the higher burning temperature. When the temperature was at 600 ℃ for 2 h, the average particle diameter was the smallest, about 20 nm. This adsorbent had strong adsorption capacity for the lead ion and cadmium ion in water at pH 4～8. The adsorption behavior followed a Langmuir adsorption isotherm and a pseudo-second-order kinetic model. The enthalpy change (ΔH) of the adsorption process was 39.312 kJ•mol－1. At various temperatures, Gibbs free energy changes (ΔG) were negative, and entropy changes (ΔS) were positive. The activation energy (Ea) was 20.359 kJ•mol－1 for the adsorption. These showed that the adsorption of cadmium ion by the nano-calcium titanate powder was an endothermic and spontaneous physical process. The adsorbed lead ion and cadmium ion could be completely eluated using 1 mol•L－1 HNO3. The pre-concentration factors for lead ion and cadmium ion were all more than 200. The method has been applied to the preconcentration and flame atomic absorption spectrometry (FAAS) determination of trace lead ion and cadmium ion in water samples. The recoveries were 96.3%～107.2% and 93.5%～104.0% respectively, and the results were found to be in agreement with those by graphite furnace atomic absorption spectrometry.

Key words: nano-calcium titanate powder, lead ion, cadmium ion, adsorption behavior, flame atomic absorption spectrometry (FAAS)