Solid-phase extraction of heavy metal ions on a high surface area titanium dioxide (anatase)

Abstract

The adsorption of heavy metal cations on two TiO₂(anatase) samples was investigated. The first sample (T1) was synthesized by hydrolysis of TiCl₄, whereas the second (T2) was a commercial product. The adsorption kinetics, pH curves, adsorption isotherms and adsorption capacities were studied. Sample T1 possesses a significant capacity towards sorption of heavy metal cations (approximately 5000 µg g^–1), which is much higher than the adsorption capacity of the commercial sample T2 and, in most instances, higher than the capacity of silica. Quantitative and fast sorption of various heavy metal ions in trace concentrations on T1 occurs, but in different pH ranges for each element. At pH 8 quantitative sorption was detected for Bi, Cd, Co, Cr, Cu, Fe, Ge, In, Mn, Ni, Pb, Sb, Sn, Te, Tl, V and Zn. All of the elements can be eluted with HNO₃ and EDTA and this procedure does not adversely affect the titania for subsequent sorptions. On the basis of the results obtained, optimum conditions for the joint and quantitative solid-phase extraction of the most common heavy metal ions are proposed. A column system for preconcentration was developed. The conditions for the quantitative and reproducible elution and of subsequent AAS were established. A method for the determination of trace elements in different waters is proposed. It is characterized by high precision, reproducibility and concentration factor.