SYNTHESIS OF TIN DIOXIDE POWDER FROM TIN TETRACHLORIDE SOLUTION BY CHEMICAL PRECIPITATION AND CALCINATION METHODS

• Main Author: Violandy, Chepy
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/87726
• Institution: Institut Teknologi Bandung

Indonesia is one of the largest tin producing countries in the world. Tin processing and refining products produced domestically include tin ingots, tin solder, tin granules and tin chemicals. Product diversification and development need to be continuously carried out to capture market opportunities and increase the added value of tin as high as possible domestically. In addition to its metal form, tin is also widely used in the form of its compounds such as stannous sulfate (SnSO4), stannic chloride (SnCl4) and stannic oxide (SnO2). Studies and research need to be carried out to develop tin-based product synthesis technology, such as tin metal nanoparticle products and their derivative compounds. One of the potential tin derivative products is SnO2 particles. SnO2 particles can be used as a reducing gas sensor, a catalyst in various reactions and as an alternative anode in lithium-ion batteries replacing graphite, and as a co-catalyst in solid polymer electrolyte (SPE) fuel cells. The synthesis of SnO2 particles, both micro and nano in size, can be done by several methods, such as the sol-gel method, hydrothermal method, precipitation method, electrospinning and chemical vapor deposition (CVD) method. The choice of synthesis method depends on the desired properties of the SnO2 particles, such as size, morphology, and purity. In this thesis research, a study was conducted to synthesize SnO2 from pure SnCl4 solution by precipitation method using NH4OH solution as Sn precipitation reagent. SnCl4 solution was obtained from PT. Timah Tbk., which is an intermediate product produced by PT. Timah Industri (a subsidiary of PT. Timah) from the reaction between chlorine gas (Cl2) and tin ingot. The dissolved tin precipitation process was carried out at two temperatures, namely room temperature and temperatures of 70, 80, and 90 oC. Preparation of SnCl4 solution was carried out by diluting the initial SnCl4 solution received from PT. Timah, Tbk. with distilled water to obtain SnCl4 precursor solution with concentrations of 0.2 and 0.5 molar. The initial SnCl4 solution received from PT. Timah, Tbk has a concentration of 15.5 molar. Furthermore, the Sn precipitation process was carried out by adding NH4OH solution into a glass reactor that had been filled with SnCl4 precursor solution with a volume of 500 mL for precipitation experiments at a temperature of 90 oC and a volume of 150 mL for precipitation experiments at room temperature. The solution was stirred using a magnetic stirrer bar until a certain pH was reached according to the variation of the experiment and Sn(OH)4 precipitate was formed. After the precipitation process was complete, the precipitate was filtered using filter paper. The precipitate was washed with deionized water to remove residual reagents and ions that were still attached. After the filtration and washing stages, the s precipitate was dried in an oven for 24 hours at a temperature of 110 oC. After drying, the next stage was the calcination process carried out in a muffle furnace at a temperature of 500 and 600 °C for 1 hour to convert Sn(OH)4 to SnO2. This calcination process was conducted to help form the crystalline structure of SnO2. Product characterization was performed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size analyzer (PSA). XRD analysis was performed on the synthesized product to ensure the formation of SnO2 particles, evaluate its crystallinity and crystal size. The crystal size was determined from the XRD data using the Scherrer Equation. SEM analysis was performed to study the morphology of the synthesized SnO2 particles. Meanwhile, analysis with PSA was performed to determine the size of SnO2 particles obtained from the synthesis experiment with variations in temperature, Sn concentration, pH, and time. In the initial concentration range of SnCl4 from 0.1 - 0.4 molar and room temperature, dissolved Sn can be perfectly precipitated (precipitation percentage > 99%) when the pH of the solution is increased to pH = 8. The XRD diffractogram obtained indicated that the powder from precipitation at room temperature and 70 oC has a structure with low crystallinity whose diffraction peaks are identified as Sn(OH)4. After calcination and XRD analysis of the calcination products at temperatures of 500 and 600 oC was performed, the XRD diffractogram of the synthesized powder show sharp diffraction peaks indicating the formation of crystalline SnO2 material. A higher calcination temperature (600 oC) produced stronger powder crystallinity compared to calcination at a lower temperature (500 oC). The calculation results using the Scherrer Equation show that the average crystallite sizes of the SnO2 powder from calcination product at temperatures of 500 and 600 oC were 5.89 nm and 12.56 nm, respectively. The calculation results of the average crystallite size from the XRD data show a larger crystallite size at higher calcination temperatures. The average particle size of the calcination product at temperatures of 500 and 600 oC obtained from the PSA analysis are 1398.3 nm and 2350.4 nm, respectively. The results of measuring the particle size of the SnO2 powder with PSA show that the resulting SnO2 powder product is in the form of micron-sized particles. In line with the results of the crystallite size analysis, increasing the calcination temperature tends to increase the particle size of the SnO2 powder synthesis product. The results of SEM analysis showed that the obtained SnO2 particles had irregular grain morphology with submicron to micron sizes. The results of SEM analysis indicated that the method of synthesizing SnO2 powder from SnCl4 solution by precipitation and calcination methods under the conditions studied in this study cannot produce nano-sized grains with spherical or rounded morphology. Further studies and experiments are still needed to obtain powder with a finer and more uniform size with a morphology that approaches spherical.