Using sorghum straw as template, porous nano-barium-strontium titanate (SPBST) was successfully prepared by the sol-gel method, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and fourier transform infrared spectrophotometry (FTIR). Its adsorption capabilities for heavy metal such as lead ion, cadmium ion and zinc ion were studied. The effects of the calcining temperature on the structure of porous adsorbent and its adsorbing capacity were discussed. Moreover, taking the cadmium ion as an example, the thermodynamics and kinetics of the adsorption were completely investigated. The results showed that the sorbents were porous, buildup perovskite nano-barium-strontium titanate, and the average particle diameters of crystalloid were not more than 20 nm. The crystalloids of the sorbent became agglomerated when the calcining temperature was too high, which was infaust for the adsorption, but it incompact when the calcining temperature was too low. The optimum condition was at 750 ℃ for 6 h. In the medium of pH 5～8, the adsorption time was 70 min, and capacity of adsorption were 191.51 mg•g^－1 for lead, 19.00 mg•g^－1 for cadmium and 19.97 mg•g^－1 for zinc. The adsorption behavior followed a Freundlich adsorption isotherm and a pseudo-second-order kinetic model. The enthalpy change (ΔH) of the adsorption process was 35.905 kJ•mol^－1. At various temperatures, Gibbs free energy changes (ΔG) were negative, and entropy changes (ΔS) were positive. The activation energy (E_a) was 62.430 kJ•mol^－1 for the adsorption. These showed that the adsorption was an endothermic and spontaneous physical process. The adsorbed heavy metal ion could be completely eluated using 1 mol•L^－1 HNO₃. The pre-concentration factors for all studied heavy metal ions were all more than 200. The method has been applied to the preconcentration and FAAS determination of trace lead, cadmium and zinc ion in water samples. The recoveries were 90.3%～103.4%, 91.5%～103.2% and 94.35%～101.1% respectively.

Key words: porous nano-barium-strontium titanate, sorghum straw, biotemplate method, adsorption behavior, heavy metal ion, FAAS