Temperature Effect on H₂S Diffusion through Nalophan^TM

Abstract

The Hydrogen sulphide (H2S) loss, an odorous molecule of small dimensions, through NalophanTM bags has been studied. The diffusion coefficient of H2S through the NalophanTM film was evaluated using the Fick’s law, and it turnedout to be equal to 7.55E-12 (m2/s) at a temperature of 23°C and a relative humidity of 60%. This D coefficient entails a reduction of 17% of H2S into 30 hours of storage time. Moreover, the role of humidity on diffusion speed was evaluated by storing the NalophanTM bags at relative humidity condition of 20% and temperature of 23°C. In this condition, the loss percentage of H2S (%) after 30 h turns out to be equal to about 23%. The results show that the diffusion phenomena are affected by the relative humidity storage condition: by decreasing the relative humidity of storage condition it is observed a weak increase of H2S (%) loss. Also the sampling at high temperature (i.e 75°C or 130°C) was evaluated by heating the filled NalophanTM bags for 5 minute respectively at 75°C and 130°C and then by storing the NalophanTM bags at relative humidity condition of 20% or 60% and temperature of 23°C. The results show a loss percentage of H2S after the heat treatment (i.e 75°C or 130°C) of the film not negligible in a range of 30-36%. This behaviour could be attributed to the proximity of the glass transition temperature of the NalophanTM.