EFFECTS OF COAGULATION MEDIA ON POLY(VINYLIDENE FLUORIDE) MEMBRANE PROPERTIES

• Main Author: Hartono, Rudi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/52151
• Institution: Institut Teknologi Bandung

Hydrophobic poly(vinylidene fluoride) membranes can become an obstacle in the filtration process, especially in the separation of polar components. This membrane property can be hydrophilic using electrolyte coagulation media. This study used KCl and NaCl solutions as coagulation media, at concentrations of 1%, 5%, and 10%. The obtained poly(vinyliden fluoride) membrane was characterized using various parameters and tested for its flux and rejection performance. The beta fraction obtained in water coagulation media was 0.44 ± 0.014. The beta fraction increased with the use of KCl and NaCl, where the beta fraction in the KCl 1% variation was 0.60 ± 0.01 and 1% NaCl 0.66 ± 0.006. The maximum beta fraction was obtained at electrolyte concentrations of 5% and 10%. The beta fraction of the membrane increases as the membrane becomes more hydrophilic. This property is also evidenced by the contact angle results obtained. The contact angle of the membrane in the water coagulation medium was 87.07 ± 0.23o. The contact angle decreases with the variation of KCl and NaCl, until the minimum contact angle is obtained at a concentration of 10%. Poly(vinylidene fluoride) membranes have great mechanical strength, however the use of electrolytes as a coagulation medium reduces the mechanical strength of the membranes. The largest pore diameter of the membrane in the water medium was 0.06 ± 0.003 µm. This pore diameter increases with the variation of KCl, so that the maximum pore diameter is obtained at a concentration of 10% 4.37 ± 0.54 µm. However, different results were obtained for the variation of NaCl, where the largest pore diameter of the membrane decreased at a concentration of 10%. Similar results were obtained for porosity, where the porosity of the membrane increased with the KCl variation and decreased at the 10% NaCl variation. This difference was caused by the pore structure of the membrane in each variation. Membrane morphology showed a different pore size in each variation, and the pore size at 10% NaCl variation was very small. This pore size affected membrane flux and rejection. The water flux in water coagulation media was 11 ± 1.3 L.hr-1.m-2. The water flux increases with the variation of KCl. The water flux at the KCl 1% and 5% variations were 11.3 ± 0.52 L.jam-1.m-2 and 15 ± 1.4 L.jam-1.m-2, respectively, and the maximum water flux was obtained at 10 % of KCl having a value of 27 ± 1.9 L.hr-1.m-2. The membrane water flux at various NaCl gave different results. Water flux at 1% and 5% NaCl variations,were 16.5 ± 1.8 L.hr-1.m-2 and 17.4 ± 2.6 L.hr-1.m-2, respectively. The water flux decreased at 10 % of NaCl, namely13.1 ± 1.1 L.hr-1.m-2. This pore size also affects the dextran rejection; smaller pore size increases membrane rejection to dextran. The rejection coefficient of dextran in water coagulation media was 98.8 ± 0.04%. The rejection coefficient of the reactant decreased with the KCl variation, until the minimum rejection coefficient was obtained at the 10% KCl variation of 93.88 ± 2.88%. The rejection coefficient of dextran in the NaCl variation gave different results. The rejection coefficient of dextran increased at 10% NaCl variation, in which its value was 95.92 ± 3.13%. This study also identified membrane rejection against certain dyes such as methylene blue and reactive orange . The first typewas positively charged while the second was negatively charged. The membrane rejection coefficient against methylene blue in water coagulation media was 85.08 ± 0.51%. This rejection coefficient increased with the KCl variation, so that the maximum rejection coefficient at 10% KCl variation was 98.27 ± 0.75%. Similar results were obtained for the NaCl variation, the maximum rejection coefficient was obtained at 10% NaCl variation. The results of this study showed that the membrane performances were influenced by hydrophilicity, porosity, and membrane pore size.