The effects of preparation parameters on the performance and morphology of polydimethylsiloxane/ polysulfone (PDMS/PSf) membranes were investigated. The PDMS layer is mainly used for sealing the defects of the PSf selective layer. The membrane morphologies were characterized by using scanning electron microscopy (SEM). The CO2/CH4 separation performance of membranes was studied by a pure gas permeation experimental set up. According to the SEM results, decreasing the water/N,N-dimethylacetamide (DMAc) ratio as the coagulation medium from pure water to mixture of 90 vol.% DMAc and 10 vol.% water resulted in complete disappearance of macrovoids and also a lowering of the membrane selectivity. Permselectivity results showed that the ideal CO2/CH4 separation factor of the membranes was improved by the presence of the non-solvent additive to the polymer solution. It was also observed that reduction of the coagulation bath temperature (CBT) led to elimination of macrovoids which affect gas separation performance. Using methanol as a coagulant resulted in a less selective membrane compared with ethanol and water as coagulants and the CO2 permeance was about 3 and 9 times greater than with ethanol and water as coagulants, respectively.

In this study, the effect of processing conditions on the performance of continuous stirred tank -ultrafiltration (CSTR-UF) in dead - end mode was investigated. An UF membrane with a molecular weight cutoff of 3 kDa made of regenerated cellulose material was used to separate enzyme from products. The effect of operating pressure ranging between 2 and 5 bar and time on the performance of the CSTR-UF system was studied. The experiments were performed with a 0.139 molar aqueous solution of lactose as feed. According to the experimental data, the lactose concentration in the permeate decreased with time due to concentration polarization and hydrolysis. It was found that the rejection factor of lactose increases from 33 to 77% with time from 5 to 85 min. Permeation flux of the membrane was evaluated in terms of pure water flux (PWF) and lactose aqueous solution. Results showed that a high operating pressure led to a high permeation flux for both mentioned cases. Also, adding lactose and enzyme to pure water caused a reduction of the permeation flux due to concentration polarization.