Simultaneous uptake of Ni2+, NH4+, and PO43- by amorphous CaO-Al2O3-SiO2 (C-A-S) compounds was investigated using batch and column methods. Fifteen different C-A-S samples with systematically varied chemical compositions were prepared by coprecipitation from ethanol-water solutions containing Ca(NO3)(2)(.)4H(2)O, Al(NO3)(3)(.)9H(2)O, and Si(OC2H5)(4), using NH4OH as the precipitating agent. The resulting precipitates were dried and heated at various temperatures to produce the C-A-S samples, which were then characterized by XRD, FTIR, solid state MAS NMR, DTA-TG, and N-2 adsorption. All the C-A-S samples prepared at 600-900 degrees C were amorphous, apart from the CaO-rich samples. Simultaneous uptake of Ni2+, NH4+, and PO43- was determined by a batch method using a solution with an initial concentration of 2 mM. In these experiments, the uptake abilities of the C-A-S samples for Ni2+ and PO43- were high, but were relatively low for NH+. The uptake abilities for Ni2+ and PO43-increased but that for NH+ decreased as the silica content in the C-A-S decreased, suggesting that similar uptake mechanisms (ion substitution and/or precipitation) are operating for Ni2+ and PO43- but the uptake mechanism for NH4+ is different (physical adsorption). The column experiments indicate that the order of uptake ability of C-A-S for the three ions is Ni-4(+) << PO43- < Ni2+. Although the silica content of the C-A-S does not have the expected influence on the uptake of these three ions, for NH4+ it plays an important role in the formation of the amorphous phase and also in the suppression of Ca2+ and/or Al3+ release from the C-A-S during the uptake experiments. The optimum uptake properties of the C-A-S can thus be controlled by adjusting the chemical compositions and heating conditions under which the samples are prepared. (c) 2006 Elsevier Inc. All rights reserved.