A cost-effective solid platform based on nanosized α-Fe2O3 chemically treated polyurethane foam for separation of chromium(VI) from water: characterization, kinetic, thermodynamic study and analytical utility

A low-cost and selective solid phase extractor (SPE) for complete removal of chromium (VI) species from aqueous media has been developed. The proposed method was based upon formation of chlorochromate [CrClO3](aq)(-) oxyanion in aqueous HCl (>= 0.5 mol/L) medium followed by complete extraction onto the ion pairing 2,3,5-triphenyltetrazolium chloride (TZ(+)Cl(-)) modified alpha-Fe2O3 nanoparticles treated polyurethane foam (PUFs) (TZ(+)Cl(-)/alpha-Fe2O3 NPs/PUFs) solid phase platform. The sorption data fitted well pseudo-second-order kinetic with an overall rate constant (k(2)) of 0.010 g (mg.min)(-1) The values of Delta H (-78.2 +/- 2.1 kJ mol(-1)) and Delta G (-3.51 +/- 1.1 kJ mol(-1)) revealed that, the [CrClO3](aq)(-) sorption onto the solid sorbent are spontaneous and exothermic process, respectively. The value of Delta S (223.5 +/- 2.5 J mol(-1) K-1 reflects the sorption of [CrClO3](aq)(-) onto the TZ(+)Cl(-)/alpha alpha-Fe2O3 NPs/PUFs sorbent proceeded in a more random fashion. The nanocomposite sorbent packed column was successfully used for complete removal of trace levels of chromium (VI) species from environmental water samples. The retained chromium (VI) species were recovered with NaOH (0.5 M) and analysed by ICP-OES. Sorbent packed column was also used for rapid and complete retention of chromium(III) after oxidation with H2O2 in KOH. The sorbent packed column can be reused for 3-4 times without decrease (+/- 5%) in column performance.