DETERMINATION OF STANDARD COMPOUND FOR MEASURING MOLECULAR WEIGHT CUT-OFF AND ITS APPLICATION TO POLYVINYLIDEN FLUORIDE/BENTONITE-3-AMINOPROPYLTRIMETHOXYSILANE MEMBRANES

• Main Author: Sri Setyawati Dewi, Rahmi
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/37774
• Institution: Institut Teknologi Bandung

In separation pmcesses, molecular weight cut-off (MWCO) is a very important parameter to determine the membrane selectivity. MWCO determination is carried out by using the rejection method of solutes with known molecular weight. Until now, dextran is still used as a standard compound due to its availability in a wide range of molecular weight and it has no charge and no interaction with the membrane. Unfortunately, the price of dextran is quite expensive; therefore, the objective of this study was to find other standard compound as an alternative of dextran. In our study, polyvinylidene .fl.uoride/bentonile-3- aminopropyltrimethoxysilane (PVDFIBNT-APS) membranes were used as the case study. Among various polymers, polyethylene glycol (PEG) was chosen to be tested as standard compound, because PEG is much cheaper than dextran, easy to obtain in various molecular weights and has similar molecular shape as dextran. PVDFIBNT-APS membranes were prepared using the phase inversion method with varied concentrations of BNT-APS up to 1% (bib). The rejection percentage (% R) of PVDFIBNT-APS membranes were measured using dextrans with molecular weights of 10, 40, 70, 150 kDa and PEGs with molecular weights of 4, 10, I 00 kDa. Dragendor.ff reagent was used for the quantitative analysis for PEG concent ration because this method was not limited to low PEG concentration only. The experimental data showed that PEG can be used as an alternative standard compound for MWCO determination. This was indicated by the similar value of%Rfor dextran and PEG with a molecular weight of 10 kDa, which were 54.88% and 54.97%, respectively. It was also found that the rejection percentage increased with increasing BNT-APS concentrations. The highest rejection percentage was found in membranes with J%(w/w) BNT-APS, showing that the addition of BNT-APS led to smaller MWCO. So, the PVDF membrane had a MWCO of 100 kDa, while PVDFIBNT-APS membrane had 92 kDa. Other characterizations included water flux, porosity, pore size and contact angle of water. It was found that the addition of BNT-APS caused the water flux to decrease by 17%, membrane porosity decreased by 21% and membrane pore size became smaller by 48%. These results were in line with the dat a of reject ion and MWCO of the prepared membranes. Moreover, increasing BNT-APS concentration produced membranes with smaller contact angle of water. The lowest value o.fwater con/act angle was.found in PVDF membrane wilh BNT-APS concentration of 1% (w/w), which was 65.3°. This result proved that the addition of BNT-APS increased !he hydrophilicity of the membrane. So, based on the results mentioned above, it could be concluded !hat our study had succeeded to prove that PEG could be used as an excellent alternative standard compound to replace dextran in measuring MWCO of the membranes and Dragendorff reagent could be used .for PEG quantitative analysis. The measurement of other membrane characteristics showed that the addition of BNT-APS in PVDF resulted in hydrophylic membranes.