Adsorption Profile of Molecular Iodine and Iodine Number of Polyurethane Foam

Abstract

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.

Keywords:

• Iodine
• Polyurethane foam
• Adsorption
• Kinetics
• Thermodynamics
• Iodine number

Acknowledgments