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 m² g^-1. The kinetic data indicates that the intraparticle diffusion rate of adsorption (R_d) and rate of mass action (k₁) 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 kJ 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 PUF. The effect of temperature on the sorption yields the thermodynamic parameters ΔH = 50 ± 2 kJ mole^-1 and ΔS = 170 ± 4 J mole^-1 K^-1. The Gibbs free energy. (ΔG) ranges from 3.72 to -2.15 kJ mole^-1, 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.