H(2)S Loss through Nalophan™ Bags: Contributions of Adsorption and Diffusion

Hydrogen-sulfide (H(2)S) is a molecule of small dimensions typically present in the odor emissions from different plants. The European Standard EN 13725:2003 set a maximum storage time allowed of 30 hours, during which the sampling bag has to maintain the mixture of odorants with minimal changes. This study investigates the H(2)S losses through Nalophan bags and it shows that nonnegligible losses of H(2)S can be observed. The percent H(2)S loss after 30 hrs with respect to the initial concentration is equal to 33% ± 3% at a relative humidity of 20% and equal to 22% ± 1% at a relative humidity of 60%. The average quantity of adsorbed H(2)S at 30 h is equal to 2.17 10(5) g(H(2)S)/g(Nalophan) at a storage humidity of 20% and equal to 1.79 10(5) g(H(2)S)/g(Nalophan) at a storage humidity of 60%. The diffusion coefficients of H(2)S through Nalophan, for these two humidity conditions tested, are comparable (i.e., 7.5 10(−12) m(2)/sec at 20% humidity and 6.6 10(−12) m(2)/sec at 60% humidity).