E. Vassileva et al., COLUMN SOLID-PHASE EXTRACTION OF HEAVY-METAL IONS ON A HIGH-SURFACE-AREA CEO2 AS A PRECONCENTRATION METHOD FOR TRACE DETERMINATION, Analytica chimica acta, 336(1-3), 1996, pp. 141-150
The adsorption of heavy metal cations on two CeO2 samples, (C-1, 204 m
(2) g(-1), prepared by hydrolysis of Ce(NH4)(2)(NO3)(6), and C-2, 123
m(2) g(-1), synthesized by hydrolysis-oxidation of Ce(NO3)(3)), has be
en investigated. Studies on (i) adsorption kinetics, (ii) pH curves, (
iii) adsorption isotherms, (iv) adsorption capacities and (v) the natu
re of the sorption sites have been performed. Quantitative sorption of
Cd2+, Co2+, Cu2+, Mn2+, Pb2+ and Zn2+ has been detected at pH greater
than or equal to 7. On the basis of IR spectra of adsorbed CO, it has
been concluded that the adsorption sites represent coordinatively uns
aturated Ce4+-O2- pairs at the ceria surface. All of the adsorbed ions
may be eluted by HNO3 and EDTA and the CeO2 sample preserves its sorp
tion properties after this procedure. Optimal conditions for simultane
ous and quantitative solid-phase extraction of the most common heavy-m
etal ions are proposed. A column system for preconcentration is develo
ped. Conditions for quantitative and reproducible elution and subseque
nt atomic absorption spectrometry are established. The system has been
tested with some analytes of particular environmental importance (Cd,
Co, Cu and Ph) in river and waste waters.