## 3 Results and Discussion
### Effectiveness of Membrane Hydropholization  
The hydrophilic character of planar membrane was turned to hydrophobic one with high efficiency. As a result of hydrophobization, the changes in morphology and physicochemistry of the membrane surface are clearly noticeable (Table 1). All membrane samples possessed contact angle values higher than 90\({}^{\circ}\). The significant increase of water contact angle confirms the formation of the hydrophobic surface. Based on results presented in Table 1, it can be concluded that modification conditions (time and type of grafting agent) have an essential impact on the resulting hydrophobicity level. The highest value of CA was found for samples modified by C18 Cl3 molecules, i.e., the molecules with the longest hydrocarbon chain (~2.3 nm). Moreover, comparing ceramics grafted by silanes possessing the same length of alkyl chains, higher CA value was found for C8 Cl3 than for C8 OEt3. This observation is related to the bond dissociation energy which is equal to 489.5 kJ mol\({}^{-1}\) and 510.5 kJ mol\({}^{-1}\) for Si-Cl and Si-OEt, respectively [60]. Similar relation was found for ceramic powders (TiO\({}_{2}\) and ZrO\({}_{2}\)) modified by non-fluorinated compounds possessing various reactive groups (e.g., methoxy, ethoxy, and chlorine atoms) [44]. The grafting process affects physicochemistry of ceramics, which was proved by the resulting reduction of surface free energy (SFE) value. It was found that polar component (\(\gamma^{\mathrm{P}}\)) in overall SFE is very small (Table 1). Small contribution of the polar part compared to the dispersive component (\(\gamma^{\mathrm{d}}\)) of SFE is characteristic for hydrophobic and highly hydrophobic materials [42; 45; 58; 61]. Hydropholization process also influences the surface roughness. The roughness parameter is reduced after grafting and it decreased even more after the extension of grafting duration. Silanization generated smoother surfaces with higher level of hydrophobicity. Namely, the smoothest surface possessing simultaneously the lowest value of overall SFE was achieved for samples modified by C18 Cl3 during 4.5 h.  
The efficiency of tubular membranes modification was assessed by determining LEPw values for alumina and titania membranes after 1.5 h and 4.5 h of modification (Figure 3). A substantial influence of grafting time on the LEPw values, especially for samples grafted by C18 Cl3 molecules (Figure 3) was observed. After 1.5 h of hydrophobization LEPw value equal to 1 bar for alumina and titania membranes were observed. Longer exposure of membranes to the grafting agent resulted \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Pristine**} & \multicolumn{2}{c}{**Ti-CSOEt3**} & \multicolumn{2}{c}{**Ti-C8 Cl3**} & \multicolumn{2}{c}{**Ti-C18 Cl3**} \\ \cline{3-8}  & & **1.5 h** & **4.5 h** & **1.5h** & **4.5 h** & **1.5 h** & **4.5 h** \\ \hline Contact angle (CA), & & & & & & & \\ deg & 40 \(\pm\) 2 & 111 \(\pm\) 2 & 113 \(\pm\) 2 & 120 \(\pm\) 2 & 128 \(\pm\) 2 & 126 \(\pm\) 2 & 132 \(\pm\) 2 \\ \hline SFE, mN\(\cdot\)m\({}^{-1}\) & 140 \(\pm\) 5 & 62.5 \(\pm\) 2.7 & 53.6 \(\pm\) 2.3 & 43.7 \(\pm\) 1.9 & 32.7 \(\pm\) 1.4 & 38.2 \(\pm\) 1.7 & 31.1 \(\pm\) 1.4 \\ \hline Polar part of SFE (\(\gamma^{\mathrm{P}}\)), mN\(\cdot\)m\({}^{-1}\) & 44.8 \(\pm\) 1.4 & 13.3 \(\pm\) 0.6 & 11.4 \(\pm\) 0.5 & 9.3 \(\pm\) 0.4 & 8.6 \(\pm\) 0.4 & 5.7 \(\pm\) 0.3 & 5.5 \(\pm\) 0.2 \\ \hline Dispersive part of SFE (\(\gamma^{\mathrm{d}}\)), mN\(\cdot\)m\({}^{-1}\) & 95.2 \(\pm\) 3.1 & 49.2 \(\pm\) 2.2 & 42.2 \(\pm\) 1.8 & 34.4 \(\pm\) 1.5 & 24.1 \(\pm\) 1.1 & 32.5 \(\pm\) 1.4 & 25.6 \(\pm\) 1.1 \\ \hline RMS, nm & 60.5 \(\pm\) 5.1 & 50.9 \(\pm\) 2.0 & 45.2 \(\pm\) 1.8 & 39.6 \(\pm\) 1.6 & 33.2 \(\pm\) 1.3 & 27.8 \(\pm\) 1.1 & 22.9 \(\pm\) 0.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characterization of modified planar ceramic membrane. in the increase of LEPw values to 7 bar and 4 bar for Al\({}_{2}\)O\({}_{3}\) and TiO\({}_{2}\) membrane, respectively.