Preconcentration and determination of trace amounts of metal ions in cast iron, granite, and water using polyurethane foam functionalized with beta-naphthol

Polyurethane foam functionalized with β-naphthol was prepared by covalently linking the reagent with the polyurethane foam matrix through –N=N– groups. The reagent-bonded polyurethane foam (β-Nap-PUF) was characterized by use of elemental analysis, UV–visible and IR spectrosco-py, thermal analysis (TGA), density, and stability. β-Nap-PUF was found to be very suitable for preconcentration and determination of nickel, cop-per, silver, and mercury ions in cast iron, granite, tap, and waste water. Va-rious conditions affecting the adsorption of Ni2+, Cu2+, Ag+, and Hg2+ on β-Nap-PUF were studied. Maximum adsorption of Ni2+, Cu2+, Ag+, and Hg2+ on β-Nap-PUF was in the pH ranges 3–9, 4–10, 9–10, and 1–5, res-pectively. Extraction of these metal ions followed first-order rate equations and the average values of k1, kM, and t1/2 at room temperature were calcu-lated 0.17 min-1, 4.68 µmol g-1 min-1/2, and 5.08 min, respectively. Uptake of the metal ions on the â-Nap-PUF was determined as a function of metal ion concentration in solution and the results were analyzed in terms of the Freundlich, Langmuir, and Dubinin Radushkevich models. Measurement of variation of adsorption of the metal ions with temperature yielded average values of ΔH, ΔS, ΔG, and ΔE of -21.4 kJ mol-1, -47.8 J K-1 mol-1, -5.9 kJ mol-1 and 9.1 kJ mol-1, respectively. The capacities of β-Nap-PUF we-re 0.2, 0.2, 0.1 and 0.07 mmol g-1 for Ni2+, Cu2+, Ag+, and Hg2+, respecti-vely. Enrichment factors >50 were achieved and the relative standard de-viation (RSD) was ~3.67. The mechanism of adsorption of the metal ion on to β-Nap-PUF is also discussed.