A batch method was used to investigate the uptake of heavy metal cations and anions by the compounds in the CaTiO3-CaFeO2.5 system, in which a series of oxygen vacancies was systematically introduced into a perovskite structure as the x-value of Ca(FexTi1-x)O3-x/2 was increased. Samples of CaTiO3, CaFe0.1Ti0.9O2.95, CaFe0.5Ti0.5O2.75, CaFe0.67Ti0.33O2.67 and CaFeO2.5 were prepared by solid mixing (SM), co-precipitation (CP) and gel evaporation (GE) methods. The resulting samples were calcined at temperatures between 400 and 1000 degrees C. The target crystalline phases differed according to the preparation method, but in most cases were formed at 700-800 degrees C. The Ni2+ sorption isotherms of all the samples were fitted better by the Langmuir model than by the Freundlich model, while in the case of H-2 PO4- sorption isotherms, these were better fitted by the latter model. The uptake ability increased with increasing x value of the samples. The maximum values for the saturated sorption of Ni2+ (Q(0)(Ni2+)= 2.83 mmol/g) and H-2 PO4- (K-F(H2PO4-)= 2.95 mmol/g) were achieved for x = 1 (i.e. CaFeO2.5) sample. (C) 2010 Elsevier B.V. All rights reserved.