Study On Purifying Preparation And Mechanism Of Ultra-Pure Quartz

It is a great significance that ultra high purity quartz preparaed with vein quartz to substitute for mountain crystal which is exhausting resource to meet domestic market demand, and breaking the passive situation which monopolized by U.S. for a long time. The purifying preparation and mechanism of ultra-pure quartz was are deeply and systematically discussed from four aspects. This article has conducted in-depth research on purifying preparation and mechanism of ultra-pure quartz from four aspects.A study has been made of mineralogy research for vein quartz ore adopting XRD, ICP-MS, transmission/reflection light microscope, polarizing microscope, EPMA, LRM, heating stage analysis technology, which has systematically analyzed the occurrence of solid, fluid inclusions and the distribution of impurity elements in crystal lattice.The vein quartz contains of a large number of inclusions. The main phase composition is K-feldspar, ablite, mica, diopside, almandine, sodium amphibole, pyrite, chalcopyrite, hematite and potassium chloride crystals. Li quid inclusions are gas-liquid phase type, main ingredients are H2O, CO2, CH4 and hydrocarbon.The trace elements like Al, Fe, Ti can replace Si by the form of isomorphism, they uniformly distributed in the lattice, while the edge has been enriched.For the first time using VBA language code of EXCEL software, systematacially calculated decomposition reaction chemical equilibrium of silicate, aluminum silicate mineral in mixed acid leaching system, constructed chemical reaction equation, the initial and final state of the reaction, the reaction equilibrium. Respectively calculated the thermodynamic parameters Gibbs free energy, equilibrium constant, ArGT0=A+BT in the process of mineral impurities decomposition under mixed acid, and drew the component distribution, Ellingham diagram.The criterion was built based on thermodynamic method about sorting rule and evaluation of mineral impurities decomposition in mixed acid leaching system. The ArGr0 of impurity mineral decomposition reaction all less than 0, as well as less than the ?iGT(?) of quartz with HF, HCl decomposition reaction. It can be seen that impurity mineral decomposition reaction can occur spontaneously. Furthermore, it's prior to quartz decomposition reaction. So quartz purification is feasible on thermodynamics.Study on the optimal parameters and purification effect of normal pressure leaching, thermal pressure leaching, vacuum roasting technology.The vacuum roasting-thermal pressure leaching combined purification process has been optimized. The content of impurity elements Al, Fe, K, Na, Ca, Mg are 7.9?0.652?1.804?15? 3.276?0.344 ?g·g-1 the ultra-pure quartz which the content of SiO2 is 99.996wt% has been prepared. The effect of combined purification process is better than signal purification process.The complex coexistence relationship and thermodynamic stability of Al-F, Si-F and Fe-F has been revealed by constructing phase Eh-pH diagram of Al-F-H2O and FeS2-F-H2O. The and ion are gradually transformed into??and with pH increasing. The reaction conditions of mineral impurities decomposition was effectively controlled by adjusting Eh and pH of the reaction system.The effect of lattice parameters change and crystal transfer on the purification of quartz is clearly observed during vacuum-roasting process.The SEM-EDS surface distribution of Al, Fe, K, Na, Ca, Mg has been revealed that the order of numerical size of characterized X-ray photons about impurity metal elements is:normal pressure leaching> thermal pressure leaching> vacuum-roasting and thermal pressure leaching.The decomposition reactions of these minerals in the mixed acid under the normal pressure are first-order reaction in this study. Under the thermal pressure, the decomposition reactions of albite and pyrite are first-order reaction, and the decomposition reactions of feldspar and muscovite are second-order reaction. Base on the diversity and complexity research of metal impurity in quartz, this study has analyzed and discussed about the macroscopic kinetics models. The removal of metal impurities Al, Fe, Na, Ca under the atmospheric pressure by leaching meet the unreacted shrinking core model, and K meet the Avrami model. The apparent activation energy of metal impurity Al, Fe, K, Na, Ca, Mg by leaching process is 5.587,5.545,95.96,8.35,5.189 and 1.338 kJ·mol-1 respectively. Under the thermal pressure, the metal impurities Al, Fe, K, Na, Mg remove process meet the Avrami model, and Ca meet the unreacted shrinking core model. The apparent activation energy of metal impurity Al, Fe, K, Na, Ca, Mg by leaching process is 58.247,80.878, 20.028,3.55,127.287 and 3.858 kJ·mol-1 respectively.