Study On Removal Fluid Inclusions In Quartz Sand By Microwave And Acid Leaching And Removal Mechanism

As quartz glass had superior physical and chemical properties, itwas more and more widely used as in optical power, opticalcommunications, SiO2thin film materials, aerospace, military and otherareas. With the continuous development of high-tech, the demanding ofhigh purity of quartz sand was increasingly high. However, quartz sandusually contained a large number of structural impurities, such as fluidinclusions, and the impurity ions, which could form bubbles andimpurities defects in quartz glass. However, the existing technology wasdifficult to fundamentally eliminate such defects. Therefore, removal thefluid inclusions and hydroxyl water （OH）-was the key to realize thepurified quartz ore instead of crystal preparation as high-end quartz glassraw materials.This article first proposed the method to remove fluid inclusions inquartz sand by microwave acid leaching. According to the selectiveheating characteristics of microwave, it was first to select the appropriatequality quartz mine suit to microwave and acid leaching process. Basedon that, the influence of microwave radiation on fluid inclusions inquartz sand was researched, the influence of acid leaching on fluidinclusions in quartz sand was researched, and he influence of microwaveand acid leaching on fluid inclusions in quartz sand was researched. Atthe same time, the mechanism of removal fluid inclusions in quartz sandby microwave and acid leaching was further researched. The mainresearch contents:（1） Using ICPMS and gas chromatograph, the impurity elementsand fluid inclusions content in crystal were analyzed as standard foroptimization quartz mine. Using ICPMS and gas chromatograph theimpurity elements and fluid inclusions content in Madagascar, HenanDengfeng, East China Sea, Hunan Huayuan, Hubei Macheng quartzmines were analyzed. The results showed that the impurity elementscontent of Madagascar mine was less than1-crystal, then Hubeimacheng mine. For fluid inclusions, the H₂O density of Madagascar mine was0.657, which was second only to East Sea, but due to thehigher levels of impurity elements in mine of East Sea, it was notsuitable for microwave and acid leaching process. Using Polarizingmicroscope and721spectrophotometer, the morphology andtransmittance of fluid inclusions in quartz sand was observed, and theresults showed that liquid filling degree and transmittance ofMadagascar mine were the highest, which was suit as the experimentalmaterials.（2） Using microwave, the quartz sand was treated, and the powerwas1000w and time was30min. Using infrared spectroscopy andpolarizing microscope, the changes of content of the water molecules ofthe fluid inclusions in quartz sand and microscopic morphology wereobserved. The results showed that the content of water molecules in themicrowave field was significantly increased and tiny liquid inclusionsgroup generated. Using microwave and acid etching, the weightlessnessand light transmittance of quartz sand under different experimentalconditions were analyzed, and the optimal process parameter wasdetermined. Liquid to solid ratio was10:1, aching time was5h,hydrofluoric acid concentration was30%.The results also showed that the water bath heating could increase theeffect of acid leaching, and with temperature increasing the effects ofacid leaching was more obvious. In addition, microwaves couldstrengthen the effect of acid leaching, and the H₂O content aftermicrowaves was far less than raw materials.When the quartz sand wasmelt into quartz glass, the number of bubbles was19in Φ6mm, which ishigher than1-crystal（21）.