Further Purification of Industrial Quartz by Much Milder Conditions and a Harmless Method

Abstract

A much "greener" and harmless leaching method for removing impurity aluminum further from industrial quartz sands by very dilute mixed acids has been presented. With the help of supersonic, the percentage of removal aluminum reached up to 52.5%/53%, that is, 17.4 ppm/17.7 ppm at 30 °C/80 °C, respectively. These results are 4.4/4.7 ppm lower than that supplied by a world famous quartz sands supplier, and the leaching conditions are much milder compared with other comparable methods: the concentration of hydrogen chloride in the mixed acid is only 10% of the others, the leaching temperature is much lower; at the same time, the operating time is only 13-20% of the others, thereby pollution of industrial strong acids and thermo-scattering is reduced substantially.

Mineralogy and Processing of Hydrothermal Vein Quartz from Hengche, Hubei Province (China)

“…(2) The gangue minerals such as muscovite, hematite, and apatite were effectively removed by a combined process of calcination and fluoride-free pressure acid leaching, while the removal rates of the most important impurity elements Al, K, and Fe were 88.2 wt %, 99.0 wt % and 98.1 wt %, respectively, for the HCl-NH 4 Cl system, and 87.5 wt %, 98.1 wt % and 98.2 wt % for the H 2 SO 4 -NH 4 Cl system. The removal rates of some elements, including Li, B, Na, P and Ti were not so high, because they might be structurally incorporated in the quartz lattice.…”

“…Quartz sand was calcinated at 900 • C for 5 h, and the calcinated quartz sand was washed by leaching and washing liquors. In a pressure-tight reaction kettle [10], the washed quartz sand was either leached by acid solutions containing H 2 SO 4 and NH 4 Cl, or HCl and NH 4 Cl. Leached quartz sand was again washed by ultrapure water 5-10 times, and then dried at 105 • C for 3 h. Following calcination, the first washing process is used to make full use of acids remained in leaching and washing liquors, and cut the cost effluent disposal.…”

“…Using H 2 SO 4 or HCl, calcinated gangue minerals can be efficiently dissolved and removed from quartz at high pressure and temperature. The NH 4 Cl is used to provide hydrogen ions with a more stable and higher concentration during the hydrolysis of NH 4 + .…”

“…Hydrothermal quartz is an important substitute of crystal quartz that has been studied in detail because it is rich in SiO 2 [3,4]. The hydrothermal quartz commonly contains a significant amount of associated minerals and fluid inclusions, which leads to difficulties in quartz processing [5].…”

“…In addition, pressure acid leaching with mixed agents consisting of acids and inorganic salts is deemed to be an effective method to dissolve and remove muscovite without using any fluorides [22]. The metallic ions in the inorganic salts are unacceptable in quartz purification because they would unavoidably drag in metallic impurities during processing, but the use of NH 4 Cl avoids the problem. Therefore, leaching systems including HCl-NH 4 Cl and H 2 SO 4 -NH 4 Cl could be introduced into quartz purification alongside the calcination process to effectively remove impurities from quartz.…”