## 3 Results
### Composite Membrane Characterisation: Before and after Exposure to ABE-Fermentation Broth
For the MDK-3 membrane, spectral signatures of a thin layer of protein and nucleic polymers on the surface are also observed. Moreover, in the case of the MDK-3 membrane, there is a maximum loss of intensity of almost all bands in the initial membrane spectrum, and the band from the carbonyl group also loses more than half of its intensity, although the band from the polypeptide chain has the same intensity as in the spectra of PHeptMS and PDecMS membranes after fouling. Thus, the spectra of all investigated membranes after exposure in the fermentation medium identify signs of polypeptide chain and nucleotides characterizing the structure of any microorganisms. Figure 7: IR spectra of the membranes in the region of 3700–1400 cm\({}^{-1}\). The affinity of a polymer to a liquid is determined by solubility parameters, which are a quantitative measure of intermolecular interactions and are calculated by the formula:  
\[\Delta_{s-p}=\sqrt{\left(\delta_{d,s}-\delta_{d,p}\right)^{2}+\left(\delta_{p,s} -\delta_{p,p}\right)^{2}+\left(\delta_{h,s}-\delta_{h,p}\right)^{2}}, \tag{7}\]  
where \(\Delta_{s-p}\) is the [PERSON] solubility parameter for the organic solvents (\(s\)) and polymer (\(p\)) interactions, and \(\delta_{d}\), \(\delta_{p}\), and \(\delta_{h}\) refer to the dispersion solubility parameter, polar solubility parameter, and hydrogen bonding solubility parameter, respectively. Based on the data [57] and calculated group contributions for polyalkylisoloxanes [58], the parameters of the remote interaction were found (Table 2). The distance parameters for PHeptMS and PDecMS polymers are quite close (Table 2). The least interaction with polyalkylisoloxanes in the studied series of solvents is observed for water. It is worth noting that the distance parameter of water-PHeptMS interaction is lower than that of water-PDecMS. The low solvent-polymer interaction distance parameter shows the high affinity of acetone to the membrane in the case of both PHeptMS and PDecMS. Because of the high affinity of acetone to the membrane, the membrane can swell. Thus, the polymer chains become more open to diffusion of molecules and an increase in the partial flux of acetone. Butanol is the next most compatible with PDecMS and PHeptMS. In addition, butanol is only partially miscible with water, unlike acetone and ethanol, which have unlimited solubility in water. This is caused by rather weak forces holding butanol molecules in water, which promote its penetration through a membrane [59]. This also results in a smaller contact wetting angle of the membrane by butanol in comparison with acetone. For ethanol, the distance interaction parameter is higher than that for butanol and acetone. Thus, the flow of ethanol across membranes will be less than that of acetone and n-butanol. The obtained correlations of the solvent-polymer interaction parameters correlate well with the data of the contact boundary wetting angles of PHeptMS and PDecMS with respect to water, acetone, ethanol, and butanol (Table 3). Contact wetting angles of commercial MDK-3 membrane are also presented in the table. As can be seen from the data presented in Table 3, the contact wetting angle by water for PHeptMS and PDecMS membranes was \(103^{\circ}\) and \(106^{\circ}\), respectively. With the increase \begin{table}
\begin{tabular}{c c c c c c} \hline
**Component/Polymer** & \(\delta_{d}\) & \(\delta_{p}\) & \(\delta_{h}\) & **\(\Delta\)s-PHeptMS** & \(\Delta\)s-PDecMS \\ \hline Acetone & 15.5 & 10.4 & 7.0 & 8.25 & 8.95 \\ Butanol & 16.0 & 5.7 & 15.8 & 11.44 & 12.15 \\ Ethanol & 15.8 & 8.8 & 19.4 & 15.88 & 16.64 \\ Water & 15.5 & 16.0 & 42.3 & 39.83 & 40.57 \\ PHeptMS & 16.77 & 2.54 & 4.83 & - & - \\ PDecMS & 16.77 & 1.97 & 4.26 & - & - \\ \hline \end{tabular}
\end{table} 
Table 2: Hansen solubility parameters.