Adsorption profile of molecular iodine and iodine number of polyurethane foam

The sorption of iodine on polyurethane foam (PUF) has been investigated. The maximum sorption of 0.01 N of iodine solution on PUF was found to be > 95% from 0.2 N HCl aqueous solution. The maximum equilibration was attained with 30 min agitation time. The iodine number was found to be 436 +/- 15 mg g(-1). The average pore diameter of PUF was 8.3 nm and total surface area was 67 m(2) g(-1). The kinetic data indicates that the intraparticle diffusion rate of adsorption (R-d) and rate of mass action (k(1)) of iodine sorption on PUF were 0.48 +/- 0.03 mmole g(-1) min(-1/2) and 52 +/- 8 mmole g(-1) min(-1), respectively. The sorption data followed both Freundlich and Langmuir adsorption isotherms in the concentration range 0.03 N to 0.15 N of iodine. The Freundlich constants C-m = 11.2 +/- 1.7 mmole g(-1) and 1/n = 0.57 +/- 0.05, and Langmuir constants M = 4.9 +/- 0.6 mmole g(-1) and b = 12.9 +/- 1.3 L g(-1) were established. The sorption free energy (E) = 5.3 +/- 0.2 U mole(-1) and loading capacity X-m = 5.15 +/- 0.45 mmole g(-1) were evaluated using D-R isotherm. The sorption energy reflects the physiosorption of iodine on PUR The effect of temperature on the sorption yields the thermodynamic parameters DeltaH = 50 +/- 2 kJ mole(-1) and DeltaS = 170 +/- 4 J mole(-1) K-1. The Gibbs free energy (DeltaG) ranges from 3.72 to -2.15 kJ mole suggesting the endothermic nature of sorption of iodine, but is favorable at higher temperatures (> 313K). The effect of different anions and cations on the sorption of iodine on PUF have been evaluated and discussed.