Barium-strontium titanate (BST) powder was prepared by using an oxalate coprecipitate method and was modified by dithizone coating through a maceration method, gaining a new sort of adsorbent. XRD, SEM and FT-IR analyses were used to characterize the powder and surface modification. The adsorption behavior of lead on the BST powder coated by dithizone was investigated. The results showed that the dithizone was coated on the BST powder through hydrogen bonding between the hydroxyl groups and oxygen atoms on the surface of the BST and dithizone. The lead ion in water could be adsorbed quantitively on the dithizone coated BST when the pH exceeded 4.0, and the adsorption equilibrium could be obtained in 5 min at room temperature. The adsorption behavior followed a Langmuir adsorption isotherm and a pseudo-second-order kinetic model. The enthalpy of adsorption (ΔH) was 19.42 kJ•mol^－1 and the activation energy (E_a) was 22.187 kJ•mol^－1 for the adsorption. The values show that the adsorption of lead ion by dithizone coated BST powder is an endothermic process. The lead ion adsorbed on the BST powder coated by dithizone could be completely eluated using 1 mol•L^－1 HNO₃. A new method for determination of trace lead ion in water based on this dithizone coated BST powder separation/preconcentration and flame atomic absorption spectrometry (FAAS) determination was proposed. The method has been applied to the determination of trace lead ion in water samples with satisfactory results.

Key words: barium-strontium titanate, coating, lead, adsorption behavior, FAAS