Selection And Evaluation Of High Purity Quartz Materials And Purification Technology Research

High purity quartz sand is important raw material of modern hi-tech industry such as fiber-optic communication, solar photovoltaic, aeronautics and astronautics and electronic semi-conductor. With the rising need of high purity quartz sand, mineral crystal is on the verge of exhaustion, and it’s replaceable raw material must be found immediately. From the point of view of the application of high purity quartz, this article conducted the research on mineralogical characteristics of quartz of different geologic origin, developed a comprehensive assessment within vein quartz, quartzite and quartz sandstone based on contrast purification test result, carried out systematic work towards the quartz rock type high purity quartz material in view of "geological genesis, scientific development and advanced utilization", and made chlorination roasting purification test towards the vein quartz with high content of lattice impurity. It has important theoretical guiding significance and great social and economic value for the selection and evaluation of high purity quartz materials and mineral processing.High purity quartz raw materials is the natural quartz mineral resources whose content of SiO2 can reached 99.9% or higher after purification using mature mineral processing technologies, it’s high purity quartz sand could satisfied the stringent requirements of the using effectiveness of modern hi-tech industry.The research result of mineralogical characteristics of different geo genetic types of quartz raw materials showed that there were significant differences in the mineralogical characteristics between vein quartz, quartzite and quartz sandstone, Qinghai vein quartz have high chemical purity, with few gangue minerals, coarse grain size and low lattice impurity content, although containing lots of gas-liquid inclusions, Qinghai vein quartz exhibited the best quality contrasted with Qinghai quartzite and Jiangyou quartz sandstone.Al, Fe, K is the main impurity elements in quartz, it is mainly from the inclusions and lattice impurities in Qinghai vein quartz, but in Qinghai quartzite and Jiangyou quartz sandstone, the terrigenous detritus and surface weathering material constituted the main sources of impurity elements. Comparative purification experiment found that Qinghai vein quartz could meet the requirements of IOTA-Std after purification, the w(SiO2) of fine sand of Qinghai quartzite reached 99.9%, and there was residual amount of some impurity elements such as Ti in purified quartz sand of Jiangyou quartz sandstone. According to the experimental results, we made a comprehensive evaluation of quartz raw materials of different types. It is found that both Qinghai vein quartz and granitic pegmatite from spruce pine region belonged to high purity quartz material, Qinghai quartzite and Jiangyou quartz sandstone were in boundary of high purity quartz material. Based on that, when there are three or more indicators reached A-level in five evaluation factors(chemical composition, particle size distribution characteristics, gangue minerals, fluid inclusions and lattice impurities), the quartz material can be identified as raw materials of high purity quartz.Prospective study of the sedimentary metamorphic quartzite type high purity quartz raw materials found that, the industrial value of Qinghai Huabowan quartzite mine was restrained by the deposition separation effect of Moshigou group. From the northwest(foreshore) to southeast(shoreface), as quartz particle size decreases, the content of muscovite gradually increases, and the w(SiO2) content of quartzite drops. The best grade ore from the northwest of the area was used to obtain the optimum flotation conditions of pH=2.5 and DDA dosage of 140 g/t, and the optimum acid leaching conditions of the acid volume ratio was 30%, the temperature was 55℃ and the time was 2h. Under the assist of ultrasonic, the sum of 9 kinds of impurity elements content could be refined to 66.65×10-6 in 0.110~0.074 mm fine quartz sand, and after the purification of Qinghai vein quartz by optimized conditions, high pure quartz sand was obtained which the total content of impurity elements is less than 10×10-6.Thermodynamic calculation results show that NH4 Cl can be used as chlorination agent, it was obtained that optimization chloride roasting conditions of temperature is 600℃, the time is 180 min, the content of of main impurity elements in quartz sand is 31.07×10-6. The refining process of quartz lattice impurities using NH4 Cl roasting may be divided into three stages, such as melting, reaction and escaping, NH4+ ionized from melting NH4 Cl and captured reactive oxygen species, then the free Cl– combined with metal ions, the chlorides formed and escaped. Chemical potential gradient and concentration gradient appeared in the chlorination roasting process, impurities on the quartz sand surface or near surface could be removed.