Pure ethanol

Titanium butoxide (TBOT) (97%), polyvinylpyrrolidone (PVP, average molecular weight: 10000 g/mol) and hydrogen tetrachloroaurate trihydrate (HAuCl₄·3H₂O ≥ 99.9%) were purchased from Sigma-Aldrich. Anhydrous benzyl alcohol (99%) and pure ethanol (> 99.9%) was purchased from Scharlau, and ethylene glycol (EG ≥ 99%), HCl (37%) and acetone were purchased at Panreac. All materials were used as-received without further purification. Milli-Q water (MQ-H₂O) was used in all experiments.

The simulated feed solution (ethanol–water) was prepared at various concentrations (2, 5, and 10 wt.%) of ethanol using pure ethanol (99.9%) (Scharlab S.L., Barcelona, Spain). Each sample was mixed in a conical flask containing 400 mL of distilled water and then mixed with a certain weighted amount of ethanol to obtain the required concentration of the simulated feed. A calibrated portable refractometer’s measurement (Balance World Inc., Model ATC-Refractometer, China) was used to measure the concertation of ethanol alcohol. The penetration of the ethanol across the membrane was detected by measuring its concentration in the aqueous solution collected in the vapor glass trap. This measured concentration was used to estimate the separation factor according to Equation (1) [12 ].
$$\mathsf{\alpha }=\frac{{\mathrm{y}}_{\mathrm{e},\mathrm{p}}/{\mathrm{y}}_{\mathrm{w},\mathrm{p}}}{{\mathrm{x}}_{\mathrm{e},\mathrm{f}}/{\mathrm{x}}_{\mathrm{w},\mathrm{f}}}$$
where $\mathsf{\alpha }$ is the separation factor or membrane selectivity, ${\mathrm{y}}_{\mathrm{e},\mathrm{p}}$ is the mole fraction of ethanol in the permeate, ${\mathrm{y}}_{\mathrm{w},\mathrm{p}}$ is the mole fraction of water in the permeate, ${\mathrm{x}}_{\mathrm{e},\mathrm{f}}$ is the mole fraction of ethanol in the bulk liquid feed, and ${\mathrm{x}}_{\mathrm{w},\mathrm{f}}$ is the mole fraction of water in the feed bulk liquid.