SEPARATION OF ZIRCONIUM, HAFNIUM, LANTHANUM AND CERIUM BY ION IMPRINTED POLYMER SOLID PHASE EXTRACTION

• Main Author: Sianipar, Aladin
• Format: Dissertations
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/34225
• Institution: Institut Teknologi Bandung

Zirconium in advanced technologies such as electronic technology, foundry technology, and nuclear technologies require high purity. The difficulties to obtain high-purity zirconium still be an obstacle. Zirconium in nature is generally associated with the hafnium element in the form of Zr(Hf)SiO4. This research was conducted to develop a separation method of zirconium from other metals, in particular, the separation of zirconium from hafnium with solid phase extraction by utilizing an ion-imprinted polymers (IIPs) as the functional material. In this study, the solid phase of IIPs was synthesized with zirconium ion as an ion imprint, and subsequently referred to as zirconium-imprinted polymers (Zr-IP). Zr-IP polymer was synthesized by bulk polymerization in the presence of styrene as a monomer, divinilbenzen (DVB) as a cross-linker, and benzoyl peroxide (BPO) as an initiator, 2-methoxyethanol as a porogen. Xylenol orange (XO) and vinilpiridin (VP) were used as complexing agents in the formation of a zirconium imprint. The polymerization was carried out at 80 °C for four hours under nitrogen gas condition. Factors affecting the synthesis such as the number of moles of complex compounds, the mole ratio of monomer to initiator, and the mole ratio of monomer to cross-linker had been studied. The ion imprint was formed by releasing zircon ion in the polymer with HCl 9M for 24 hours. The effect of pH, the ratio between the polymer mass to solution volume, and the contact time of the polymer with solution were also studied to characterize the retention properties of Zr-IP. Zircon ion imprint were obtained by formation complex of ZrXO and (Zr)(XO)(VP)2. The optimum conditions of the separation performance of zircon ion were obtained by using 0.1 mmol complex compounds. The mole ratio of styrene/BPO, and the mole ratio of styrene/DVB, 40/0.6 and 40/40, respectively. The unleached and leached polymers were characterized by the surface area and porosity analysis according to the method of Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), optics photograph, transmission electron microscopy (TEM), scanning electron microscope-energy disperse X-ray spectrometry (SEM-EDX), infrared spectrometry (FTIR), X-ray diffraction (XRD), and thermogravimetry analysis-differential scanning calorimetry (TGA- DSC). The significant color change of polymers before and after leaching was observed through the optics photograph from purple to red colors. The polymers with the binary complexs both before and after leaching had the similar infrared spectrum pattern, but there was the shift of wavenumber and the different intensity. The absorption peaks at 1379 cm-1 of the polymers before leaching shifted towards larger wave numbers ie 1383 cm-1 after leaching, whereas polymers with the ternary complex showed no absorption peak in this region. Nevertheless, in the range of wave numbers 3100-2900 cm-1, it was found four absorption peaks for leached polymers, and one absorption peak for the unleached polymers. In the wavenumber range of 1100-1068 cm-1 and 1030-990 cm-1, the infrared spectrum of leached polymers had three and two peaks, respectively, while the unleached polymers was found only one absorption peak. Microstructure morphology shown in SEM micrograph of the two polymers prior to leaching is more subtle with brighter imaging effects than the polymer after leaching. This indicates the releasing zircon ion from polymers, and this result is supported by analysis of the EDX spectra showed no zircon ion. TEM image of the polymer prior to leaching is denser and darker; while the polymer after leaching seems looser and brighter indicating the polymers are more porous after leaching. Porosity of polymer as indicated by analysis of BET/BJH show that the polymers after leaching has larger total volume and pore diameter size. TGA-DSC curves of Zr-IP show that XO and VP as complexing are still stuck in the polymer even though after leaching by HCl 9M. Zircon ion separation from other metal ions such as Hf (IV), La (III), Ce (IV), Ti (IV) and Fe (III) with Zr-IP as adsorbent has been studied and applied to samples resulted by destruction of zircon sand. The metal ions in the solution phase were analyzed by ICP-AES. Optimum retention capacity of Zr-IP for zircon ion at pH 5 is 6.2 mg Zr/g Zr-IP for complex Zr binary and 25.87 mg/g Zr-IP for ternary complex. The contact time among Zr-IP to a solution was required for 30 minutes to obtain the percentage of extraction more than 99%, by the ratio of the volume of solution to mass of polymer is 125 mL/g Zr-IP for binary complex and 250 mL/g Zr-IP for ternary complex. The elution of zircon ion from the polymer phase was carried out with HCl 3M. The relative selectivity coeficient (?r) of Zr-IP with the binary complex for couples Zr/Hf, Zr/La, Zr/Ce, Zr/Ti and Zr/Fe was 530, 660, 410, 160, and 340, respectively. The relative selectivity coeficient (?r) of Zr- IP with ternary complex for couples Zr/Hf was 13.18. The destruction of zircon sand in alkaline condition was carried out at temperature of 800°C for 2 hours. The optimum mass ratio of zircon sand/NaOH was observed above 1/2. The result of zircon destruction was made in the form of zircon oxychloride and then it was extracted by using Zr-IPs. Zircon ion was obtained about 33.7 mg/L with percentage of extraction of 93.61%. The ions of hafnium and titanium were still contained in the extractant, while ions of lanthanum, cerium, and iron were not detected by ICP-AES. The purification method that was established in this researched. The purity of zircon oxide from zircon sand can improve up to 97.18%. The separation of zircon ion from other metal ions has been successfully conducted for solution sample resulted from the destruction of zircon sand. The selectivity coefficient of zircon ion toward Hf by using Zr-IP is much better than that of the results of previous studies.