Adsorption behavior of noble metal ions (Au, Ag, Pd) on nanometer-size titanium dioxide with ICP-AES.

The adsorption behavior of gold (Au), silver (Ag) and palladium (Pd) on nanometer-size titanium dioxide (NSTD) at low concentrations was studied using inductively coupled plasma atomic emission spectrometry (ICP-AES). A preconcentration procedure of the analytes was carried out using NSTD as a solid-phase extractant before their determination by ICP-AES. The optimum conditions for adsorption were studied in detail, and under the condition that Au, Ag and Pd ions could be adsorbed and recovered quantitatively. The static adsorption capacities of Au, Ag and Pd on NSTD were 22.63, 14.06 and 11.82 mg/g, respectively. For the elution of gold, silver and palladium, a mixture of 5% thiourea solution and 3 mol L(-1) HNO3 was used. The parameters tested included: pH conditions, contact time of the analytes with NSTD, flow rate, adsorption capacity and sorption kinetics. According to the definition of IUPAC, the detection limits (3sigma) of this method for Au, Ag and Pd with an enrichment factor of 50 were (0.016), (0.006) and (0.012) microg mL(-1), respectively, the relative standard deviations (RSD) were 8.7%, 4.5% and 7.4%, respectively (n = 6). Some geological samples were determined with satisfactory results.