## 2 Materials and Methods
### Membrane Characterization  
* Fourier Transform infrared spectroscopy (FTIR) The chemical structures of the CA and CA/PAA membranes were investigated by Fourier Transform infrared spectroscopy (FTIR) (IRAffinit-IS, Shimadzu Corporation s.r.l., Kadikov--Istanbul, Turkey) in the spectral range of 4000-400 cm\({}^{-1}\). Five different points in the membranes sample were analyzed. The spectra were obtained with a resolution of 0.5 cm\({}^{-1}\). * Scanning Electron Microscopy (SEM) CA and CA/PAA UF membranes morphology were analyzed via scanning electron microscopy (Zeiss EVO MA 100, Assing, Italy). SEM pictures of both the membranes surface (top and bottom side) and cross section pictures were acquired. In particular, cross section samples were prepared fractured the membrane in liquid nitrogen. Before the observation, the samples were sputter-coated with a thin gold film using a rotary pumped coater (Quorum Q150R S, Quorumtech, Lewes, UK). * Differential Scanning Calorimetry (DSC) Further investigations on the properties of the CA-PAA blend were carried-out by studying the thermal behaviour of the prepared membranes in terms of glass transition temperature (Tg), melting temperature (Tm), and degradation temperature (Td), measured by differential scanning calorimetry (Heat flux DSC 4000, Perkin-Elmer, Japan). The samples were heated from 0 \({}^{\circ}\)C to 450 \({}^{\circ}\)C at a controlled heating rate of 10 \({}^{\circ}\)C/min, with accuracy of \(\pm\)0.1 \({}^{\circ}\)C and precision \(\pm\)0.02 \({}^{\circ}\)C.
* Contact Angle CA and CA/PAA UF membranes' hydrophilicity was evaluated using extension theta automated optical tensiometer (ATA Scientific, Taren Point, Australia). Ten measurements for each membrane were performed using ultra-pure water (5 \(\upmu\)L, volume of the drop), at room temperature. The average values and the standard deviations were reported. * Water Content (%) The water content of the membranes (affinity towards water) was estimated through a series of gravimetric measurements according to protocol already described in literature [30]. Membrane samples were initially cut (1 cm\({}^{2}\)) and then immersed in deionized water for 24 h at room temperature. Subsequently, the wet samples were weighted (W\({}_{\text{w}}\)), \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Membrane Name**} & \multicolumn{2}{c}{**Blend Composition**} \\ \cline{2-3}  & **CA wt. \%** & **PAA wt. \%** \\ \hline M0 & 100 & 0 \\ \hline M8 & 92 & 8 \\ \hline M15 & 85 & 15 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Composition of the polymeric solutions employed for membranes preparation. dried for 48 h at 60 \({}^{\circ}\)C, and weighted once again (W\({}_{\text{d}}\)). The percentage of water content was calculated using the Equation (1):  
\[\%\text{ Water uptake }=\frac{\text{W}_{\text{w}}-\text{W}_{\text{d}}}{\text{W}_{ \text{w}}}\times 100 \tag{1}\]  
For each membrane, three measurements were performed and the average values and corresponding standard deviation were calculated and reported. * Porosity (\(\%\)) and Pore Size CA and CA/PAA UF membrane porosity (\(\varepsilon\)) was determined by gravimetric method [29; 31], employing Equation (2): \[\varepsilon=\frac{\text{W}_{\text{w}}-\text{W}_{\text{d}}}{\text{A}\times 1 \times\rho}\times 100\] (2) where A, I, and \(\rho\) are the membrane filtration area (cm\({}^{2}\)) and the thickness (cm) of membrane and the density of water (0.998 g cm\({}^{-3}\)), respectively. In addition, the mean pore radius was performed through the Guerout-Elford-Ferry equation (Equation (3)) [32]: \[\text{r}_{\text{m}}=\sqrt{\frac{(2.9-1.75)8\eta\text{IQ}}{\varepsilon\Delta \text{P}}}\] (3) where \(\varepsilon\) (\(\%\)) is the average porosity of the membrane, \(\eta\) is the water viscosity (8.9 \(\times\) 10\({}^{-4}\) Pa s), I is the membrane thickness (m), Q is the volume of permeate water per unit time (m\({}^{3}\) s\({}^{-1}\)), and A is the membrane effective area (m\({}^{2}\)) and \(\Delta\)P (MPa) the operational pressure.