Preconcentration and Determination of Trace Amounts of Metal Ions in Cast Iron, Granite and Water Using Polyurethane Foam Fun

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 spectroscopy, thermal analysis (TGA), density, and stability. β-Nap-PUF was found to be very suitable for preconcentration and determination of nickel, copper, silver, and mercury ions in cast iron, granite, tap, and waste water. Various conditions affecting the adsorption of Ni, Cu, Ag, and Hg on β-Nap-PUF were studied. Maximum adsorption of Ni, Cu, Ag, and Hg on β-Nap-PUF was in the pH ranges 3–9, 4–10, 9–10, and 1–5, respectively. Extraction of these metal ions followed first-order rate equations and the average values of k1, kM, and t1/2 at room temperature were calculated 0.17 min, 4.68 μmol g min, and 5.08 min, respectively. Uptake of the metal ions on the β-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 ∆H, ∆S, ∆G, and ∆E of −21.4 kJ mol, −47.8 J K mol, −5.9 kJ mol and 9.1 kJ mol, respectively. The capacities of β-Nap-PUF were 0.2, 0.2, 0.1 and 0.07 mmol g for Ni, Cu, Ag, and Hg, respectively. Enrichment factors >50 were achieved and the relative standard deviation (RSD) was ~3.67. The mechanism of adsorption of the metal ion on to β-Nap-PUF is also discussed.