Chemical Speciation of Chromium(III) and (VI) Using Phosphonium Cation Impregnated Polyurethane Foams Prior to Their Spectrometric Determination

Fast and selective sorptions of Cr(VI) species from aqueous media onto tetraphenylphosphonium bromide (TPP+center dot Br-) physically immobilized polyurethane foams (PUFs) sorbent were achieved. Based on the Scatchard model of binding sites of the PUFs and Langmuir and Dubinin-Radushkevich (D-R) adsorption models of Cr(VI) retention onto TPP+center dot Br- immobilized PUFs, a dual retention mechanism involving absorption related to weak-base anion ion exchange and an added component for surface adsorption was proposed. Thus, the TPP+center dot Br- loaded PUFs were successfully packed in column mode for preconcentration of trace and ultra trace concentrations of Cr(VI) as halochromates [CrO3C](-)(aq) from aqueous HCl media. The retained [CrOCl3](-)(aq) species were recovered with NaOH (1.0 mol L-1) and analyzed by flame atomic absorption spectrometry. Cr(111) species after oxidation to Cr(VI) with H2O2 in aqueous KOH (1.0 mol L-1) were also retained and could be recovered by the proposed method. The limits of detection (LOD) and quantification (LOQ) of Cr(VI) were 0.04 and 0.13 mu g L-1, respectively. The chemical speciation of Cr(III, VI) species in various water samples at trace and ultra trace levels were carried out by TPP+center dot Br- loaded PUFs packed column. The enhancement factor and sensitivity factor of [CrO3C](-)(aq) sorption were 80.0 and 30.0, respectively.