Characterization of solid-phase extraction of Fe(III) by unloaded polyurethane foam as thiocyanate complex

This work presents a detailed study about the adsorption of iron(III)-thiocyanate complexes onto unloaded polyether-type polyurethane foam (PUF). A novel strategy was employed for this purpose, utilizing the adjustment of the plug cylinder of PUF to the arm of an overhead stirrer. The system was characterized in relation to equilibrium and kinetic aspects and it was modeled by applying Langmuir and Freundlich isotherms. The results obtained showed that adsorption occurs on a monolayer and that external transport of the solute from solution to adsorbent was the rate-determining mechanism. A maximum adsorption capacity of 2.06 x 10(-4) mol Fe g(-1) was obtained under established experimental conditions (0.5 mol L-1 SCN- and 0.005 mol L-1 HCl). Sequential extraction experiments were carried out by changing PUF in time intervals previously defined (5, 20, and 40 min), and the obtained results showed that it is possible to remove around 95% of the Fe(III) in solution through five consecutive extractions of 5 min with five 200 mg PUF cylinders. (c) 2007 Elsevier Inc. All rights reserved.