POLY(VINYLIDENE FLUORIDE)IBENTONITE AMINOPROPYLTRIMETHOXYSILANE (PVDFIBNTAPS) HYBRID MEMBRANE FOR DYES MICROFILTRATION

• Main Author: Pramono, Edi
• Format: Dissertations
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/42666
• Institution: Institut Teknologi Bandung

Poly(vinylidene fluoride) (PVDF) membrane had been widely used in water treatment due to excellent properties such as high mechanical, thermal stability and chemical resistance. Surface fouling of PVDF membrane is the main problem on the application. Some modification had been carried out to improve membrane performance and to reduce fouling on membrane surface. Modifications with addition of hydrophilic inorganic materials are widely conducted because it is easy to prepare and improved its mechanical and thermal stability, and membrane performance. Clay is abundant, inexpensive hydrophilic material and has great potential as additive for PVDF ultrafiltration and microfiltration membrane. Previous research reported the utilization of monmorillonite (MMT) grafted with polyvinyl pyrrolidone could improve membrane selectivity toward bovine serum albumin (BSA), while the addition of cloisite 15A (CLS) and palygorskit increased the abrasion resistance. Another type of clay that is promising as inorganic filler on PVDF membranes is bentonite (BNT). Bentonite is cheap and abundanly found in Indonesia. However, the addition of BNT as inorganic filler in PVDF ultrafiltration membranes has not been investigated yet. Direct mixing of clays and polymer often produces low miscibility solution that due to large difference of surface tension of polymer and clays. This phenomenon tends to form agglomeration and produces low homogeneity of composite membranes. One of the alternatives to solve this problem is to add silane groups to decrease clays surface tension; therefore it will more be easily to interact with polymers. This research aims to study the effects of BNT and 3-aminopropyltrimethoxysilane (APS) modified BNT (BNTAPS) as additive of PVDF membranes on surface properties, thermal and mechanical stability, and ultrafiltration performance of dyes solution. Chemical modification of BNT with APS was carried out in various solvent at room temperature. The PVDFIBNT and PVDFIBNTAPS hybrid membranes were prepared by phase inversion using N,N-dimetylacetamide (DMAc) as solvent, polyethylene glycol (PEG) as pore agent, and water as the coagulation medium. BNT concentration was varied from 1% to 5% w/w, while BNTAPS 0.25% to 1% w/w. The composite membranes were characterized by surface properties using Attenuated Total Reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and water contact angle, surface composition with X­ ray photoelectron spectroscopy (XPS), thermal properties with Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA), mechanical properties with tensile strength analysis, membrane morphology with scanning electron microscope (SEM), membrane topography with atomic force microscope (AFM), and permeability - selectivity toward dyes solution. BNTAPS was successfully synthesized using water as dispersion media. The FTJR spectra revealed the presence of peaks at 1566 cm- 1 and 1499 cm-1 which indicated the vibration of aminosilane. The XRD and TGA analysis proved that the APS was adsorbed and chemically bounded on the surface and d-spacing of BNT The utilization of water as dispersion media produced high yield of total silane bounded on BNT because the solvent facilitated the interaction of APS both on the BNT surface and in the basal spacing of BNT The addition of BNT with various concentration about 1% to 5% w/w produced solid flats membranes with light brown color. The ATR-FTIR data showed that the PVDF polymers consisted of a and fJ phase structures revealed by the presence of peaks at the wavenumbers of 763 cm- 1 and 840 cm-1 respectively. The BNT addition icreased fJ fraction and reduced water contact angle. The membrane fJ fraction increased from 43% to 48%. The Increasing BNT concentration decreased the membranes porosity and water permeability; however it increased the membrane selectivity toward Dextran T-500. The rejection of hybrid membranes towards methylene blue (MB) was above 90% and increased with increasing of BNT concentration. Meanwhile, the Reactive Yellowl45 was rejected above 90% by membrane with 1% w/w BNT Mechanical properties of hybrid membranes elevated up to addition of 3% BNT but reduced afterwards. The PVDFIBNTAPS with 0.25% to 1% w/w were well prepared and produced homogeneous membranes. The presence of BNTAPS on the membrane surface was indicated by XPS data in the Si2p core peak at 102-105 eV The typically pattern of PVDF as membrane component was also confirmed by XPS data at C1s peak at 208 - 292 eV. EDAX data revealed new peak of Al and Si elements for hybrid membranes. The a and fJ phase of PVDF polymorph were revealed by ATR-FTIR data. increasing concentration of BNTAPS reduced PVDF fJ fraction namely 45% for pristine PVDF to 44% for BNTAPS 1% w/w. The addition of BNTAPS decreased the thermal stability of hybrid membrane where increasing BNT concentration reduced the initiation of degradation temperature. Young modulus showed that the addition of 0.5% and 1% w/w of BNTAPS increased the mechanical strength. Water contact angle data exhibited that BNTAPS could raise hidrophilicity of membrane surface. The water permeability was improved by the addition of low BNTAPS concentration, however it was declined at higher BNTAPS concentration; these results was also supported by membranes porosity data which showed that the porosity was reduced with the increase of BNTAPS concentration. The rejection towards MB (methylene blue) dyes solution achieved above 90% and increased with increasing of BNTAPS concentration, while the rejection towards anionic Acid Yellow 17 (AY17) dye was between 60% - 80%. The dye filtration was influenced by the pH of feed solution. The rejection percentage increases up to 99% at pH 7 and 9 for all membranes. The rejection of AY 17 slighly increased with the increase of pH solution, and the %R values were still lower than PVDF pristine membrane. Flux recovery ratio data informed that the addition of BNTAPS produced better fouling resistance than PVDF pristine membrane toward dyes. Morphology data resulted asymetric membranes with sponge-like pores and finger-like pores. The addition of BNTAPS reduced the length ratio offinger like pores that caused higher membrane selectivity. So, based on surface properties, mechanical properties, and membrane performance data, it can be concluded that PVDFIBNT and PVDFIBNTAPS hybrid membranes have the potent to be applied in the dye purification. The optimum composition for hybrid membranes was 1% w/w ofBNT and 0.5% w/w ofBNTAPS.