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ZEOLITE AND ACTIVATED CARBON FOR PROTON EXCHANGE MEMBRANE FUEL CELLS ( zeolite-and-activated-carbon-for-proton-exchange-membrane-fu )

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VOL. 17, NO. 1, JANUARY 2022 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences ©2006-2022 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com and PVDF. Material with high porosity and superior specific surface area is targeted as a promising candidate for PEM. The properties of produced membrane were studied including its water uptake, swelling ratio, ion exchange capacity, and proton conductivity. 2. MATERIAL AND METHODS 2.1 Materials Local product of natural zeolite Bogor was supplied by PT Astarindo (Bogor, Indonesia), activated carbon was supplied by AJAX Chemical (NSW), PVDF binder for Li-ion battery electrodes grade 80g/bag-EQ-lib- PVDF (MTI, China). Natrium hydroxide, ammonium chloride, and sodium chloride were purchased from Merck (Japan). 2.2 Alkali Treatment and Characterization of Natural Zeolite Natural zeolite (NZ) Bogor (20 g) was introduced into NaOH solution (0,1 M, 400 mL) under stirring at 75 oC for 2 h. Subsequently, the resulting slurry was quenched to room temperature. It was then filtered, washed with distilled water to get pH around 7 and dried at 100 oC for 12 h. Then, the sample was added with NH4Cl solution (1 M, 150mL) at 80 oC for 8 h. The mixture was filtered and rinsed with distilled water until it was free from Cl- ions. Then it was dried at 100 oC for 12 h, followed by calcination at 550 oC for 4 h. NZ and alkali-treated natural zeolite (A T -NZ) were then characterized. The thermal stability of the samples was assessed under a nitrogen atmosphere using thermogravimetric analysis and differential scanning calorimetric (TGA/DSC) (Linseis STA PT 1600). The specific surface area, pore size distribution, and pore volume were estimated by the Barret-Joyner-Halenda (BJH) and Braunauer-Emmmet-Tellers (BET) method using surface area analyzer (Micromeritic Tristar II 3020 2.00). Crystallization behaviour was investigated with x- ray diffraction with Cu Kα-radiation (XRD PaNalytical Aeris). The particle morphology was observed by a Scanning Electron Microscope (PhenomWorld). 2.3 Casting of Proton Exchange Membrane PEM was prepared by mixing NZ (2 g), PVDF (5 wt%), and activated carbon (variation of 3, 5, and 7 wt%). The mixture was casted using carver hot press under pressure of 300 MPa at 200 oC for 20 min, followed by calcination at 500 oC for 2 h. The resulting membrane was quenched to room temperature and designated as NZ-3, NZ-5, and NZ-7 for filler activated carbon mass variation of 3, 5, and 7 wt%, respectively. NZ membranes were tested water uptake and swelling ratio as a preliminary study for the next experiments of AT-NZ. 2.4 Membrane Performance Experiments 2.4.1 Water uptake and swelling ratio The membrane water uptake and swelling ratio were measured by first recording the dry mass of membrane and compared it with the wet one. The membrane was dried at 60 oC for 2 h and kept in a desiccator to cool down to room temperature, then measured its dry mass. While, the membrane was immersed in deionization water for 24 h at room temperature, then taken out, dried with paper tissues and measured its wet mass was [23]–[25]. The water uptake was calculated as follow: Wdry−Wwet water uptake = W x100% (1) Swelling ratio = D wet where Wwet (g) is the mass of wet membrane and Wdry is the mass of dry membrane. The change observed in membrane thickness water uptake was used to determine the swelling ratio (%) by using Eq. (2). x 100% (2) where, Dwet (mm) and Ddry (mm) refer to the thickness of Dwet−Ddry dry the wet and dry membranes [26]. 2.4.2 Ion exchange capacity Ion exchange capacity (IEC) of the membranes was determined by titration method. The dried composite membrane was soaked in a NaCl solution (1M 50 ml) for 24 h at room temperature to substitute H+ with Na+. Then, the exchanged H+ ion in the solution was titrated using 0,01 M NaOH solution with phenolphthalein as the pH indicator. The IEC value was obtained using the following eq. (3) [25] −1 VNaOH ×MNaOH IEC(meq.g )= Wd (3) where VNaOH is the volume of NaOH in the titration (ml), MNaOH is the concentration of NaOH (mol/L) and Wd is the mass (g) of the dry membranes. 2.4.3 Proton conductivity Proton conductivity membrane was measured by electrochemical impedance spectroscopy (LCR and Impedance meter HiTester HIOKI 3522). Measurement frequency range is between 2 MHz to 100 Hz. The proton conductivity (σ in S/cm) of the membrane is determined from the following eq. (4) T σ=RS (4) where T is the thickness of the membrane (cm), S is the surface area of membrane (cm2) and R is membrane resistance (Ω) [23]. 3. RESULT AND DISCUSSIONS 3.1 Effects of Alkali Treatment on the Physicochemical Properties of Natural Zeolite AT-NZ was characterized using TGA/DSC to determine weight loss, decomposition, and thermal 59



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