Abstract

A two-parameter model was applied to describe the activity coefficient for a culture medium, and, compared with Henry's law for water, Henry's law fitted to experimental data, the extended UNIQUAC model, and experimental data obtained from an experimental setup system, consisting of a liquid culture media Thiobacillus (ATCC 290) with hydrogen sulfide (H2S), dimethyl sulfide (DMS), methyl mercaptan (MM), and dimethyl disulfide (DMDS), separately. The R-2 and R-adj(2) coefficients obtained from the analysis show that Henry's Law for water gives lower or null determinations than Henry's Law adjusted. Adjusted Henry's Law shows lower determination coefficients than the two-parameter model (with differences in R-adj(2) between 0.69% and 3.64%), except for DMS (R-adj(2) = 95.88% for adjusted Henry's Law and R-adj(2) = 94.00% for two-parameter model). The extended UNIQUAC model presents lower determinations than the other models for all compounds except H2S. On the other hand, this species has the worst comparative fits in all the models reviewed, even when Henry's law was adjusted, which may be associated with its effective solubility in the complex culture medium where the study was carried out. The ANOVA test for model discrimination shows that, for H2S, MM, and DMDS, the two-parameter model significantly represents better the liquid-vapor distribution for such components, precisely when the gas concentration was upper 300 [ppm]. In complex culture media very different from pure water, adjusted models to describe the liquid-vapor equilibrium are necessary due to the high deviations compared to pure water. In the case of the culture medium, using Henry's Law is not sufficient to describe the equilibrium for H2S, MM, and DMDS.