Introduction: Found application as furnace linings in iron and steel industry, as casting filters in several casting techniques, for color setting in paint industry, due to its ionic conductivity in electroceramics, zirconium oxide is mainly used in the production of hard ceramics in dentistry such as the laminate veneers or in textile industry as spinning rolls. The demand of zirconium oxide is mostly provided by importers from countries such as Italy, Australia, Germany, England, Netherlands and Republic of South Africa. The annual zirconium oxide consumption is about 1800-2000 metric tonnes per year. According to data of Turkish Statistical Institute in 2015, zirconium silicate cost about 30 million US dollars and zirconium oxide about 59 million US dollars were imported. Purpose: A sustainable manufacturing technique was aimed to produce the zirconium oxide which is imported every year with high cost. Scope: Development of a new sustainable refining process of zirconium oxide from zirconium silicate sand in Turkey. Limitations: In this research, main limitation is economic constraints and profit/loss analysis, but also environmental concerns in the design of this process. Utilizing minimum amount of chemicals of affordable prices and distilled water, considering electrical consumption during processes, also repetition of the process in order to dissolve all the zirconium and at the end of the process, the neutralization of acidic solutions were procedures applied to meet these limitations. Method: Firstly, zirconium silicate sand was ground and homogenized. Theoretically, in order to dissolve zirconium oxide of 250 kg, NaHSO4 about 317 kg is needed. Then for the dissolution process of zirconium silicate sand, zirconium is subjected to fusion with NaHSO4 at 600 oC. After fusion, obtained mixture is leached by hot distilled water. At the end of each process, decantation and filtration techniques were used and unreacted ceramic residue was taken into process again and the same procedures were repeated till a significant amount of zirconium was found in the solution which was determined by titration. The pH of the solution was about 0. Using caustic solution, pH was arranged to 1, as the solubility product constant of Zr(OH)4 is very low, zirconium was precipitated as zirconium hydroxide (Zr(OH)4) meanwhile other metals remained in the solution. Following drying for 24 h at 105 oC, the zirconium hydroxide was thermally decomposed at 500 oC to obtain zirconium oxide. Zirconium oxide was subsequently ground for the further analysis. The XRF, XRD and SEM-EDS analyses were carried out. In order to establish the purity of zirconium oxide samples titrations were performed. It was found that the produced zirconium oxide can successfully be used in various applications including dentistry. Results: The production of zirconium oxide of more than 99 % of purity was attained. The XRD results and EDS analysis indicated the mono phase zirconium oxide and zirconium and oxygen peaks, respectively. Conclusion: The production of zirconium oxide of more than 99 % of purity with feasible budget comparing to importation was shown possible with the evidence of XRF, XRD and SEM + EDS analysis.
Key words: Zirconium silicate, zirconium oxide, hydrometallurgy, thermal decomposition.
Author note: This work has been financially supported byThe Scientific and Technological Research Council of Turkey under the programme of TUBITAK 2209 grant to
Anahtar Kelimeler: Zirconium silicate, zirconium oxide, hydrometallurgy, thermal decomposition.
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