Research On Environmental Protection Technology For Purification And Processing Of High Purity Quartz

High-purity quartz is a key supporting material in high-tech fields such as solar energy,semiconductors,integrated circuits and optical fibers.The purity of Si O₂ in its high-end products is greater than 99.998%.As the domestic high-purity quartz high-end products still cannot fully meet the requirements of the application standards,it still relies on a large number of imported high-purity quartz raw materials and products from abroad to meet the domestic market demand.In order to break the long-term restriction in this field by the United States,it is of great significance to independently master the purification and processing technology of high-purity quartz,and to be able to use domestic quartz ore resources to prepare w（Si O₂）≥99.998%（4N8）high-purity quartz.In this paper,4N8 high-purity quartz is purified and prepared from a raw quartz ore（code-named LHC02）in a certain area of my country.In response to the national industrial environmental protection policy,the fluorine-containing wastewater generated during the acid leaching purification process is tested and treated to achieve the national comprehensive sewage discharge.Standards,and finally based on the selection of experimental process parameters,preliminary design of high-purity quartz acid leaching and purification and wastewater treatment process flow,and estimation of the cost of chemicals for process operation.This article takes the vein quartz raw ore code-named LHC02 as the object to test the purification effects of eight acid formulations.The calcination-water quenching process is used to treat the quartz block samples,and the effects of calcination temperature and water quenching times on the quality of quartz purification are studied,and the purified LHC02 raw quartz ore is determined Process parameters such as the acid formula,calcination temperature,and water quenching times.In view of the strong acidity and high concentration of fluoride in the acid leaching wastewater,calcium oxide is used to adjust the p H value of the wastewater and remove fluoride.However,the precipitate produced after the treatment settles slowly,so polyaluminum chloride（PAC）and polyacrylamide are used（PAM）Improve the sedimentation performance of the sediment.The following research results are obtained through experiments:（1）Through the comparison of the purification effects of eight acid formulas,the purification effect of the acid formula containing HF is obviously better.The total amount of impurities is reduced by 60～80ppm compared with the purification result of the acid formula without HF.The purity of the purified quartz product is uniform.More than 99.998%,the highest purification effect of the acid formula without hydrofluoric acid can only reach 99.99323%of Si O₂ content.Therefore,if you want to purify LHC02vein quartz to 4N8,you must choose an acid formula containing HF.The calcination and water quenching process process LHC02 quartz block samples.The increase in the number of water quenching does not significantly increase the purification effect of quartz,and the purification effect is best when the calcination temperature is 1000°C.Determine the calcination temperature of 1000°C,the processing technology of water quenching once.（2）The lime precipitation method is used to treat fluorine-containing wastewater,and the acid leaching waste liquid and cleaning wastewater are treated separately and mixed.Compared with the two treatment methods,the mixed treatment method is more suitable.Process parameters such as CaO dosage,mixing time,and mixing speed were optimized through single factor and orthogonal experiments,and the best combined process plan was obtained.In this experiment,only adding CaO to treat fluorine-containing wastewater can make the fluoride ion concentration of the effluent less than10mg/L.By measuring the concentration of calcium ions in the solution,the theoretical calculation is verified.The analysis is due to the high ratio of HCl and H₂SO₄ to HF in the acid leaching wastewater.The reaction with CaO makes the concentration of Ca²⁺in the solution higher,and the common ion effect is used to further reduce Ca F₂ The solubility in water promotes the formation of Ca F₂ precipitation.The lime precipitation method can not only remove the fluoride ions in the acid leaching wastewater,but also greatly reduce the sulfate content in the wastewater,reduce the concentration of impurity ions in the water quality,and facilitate recycling.（3）Aiming at the problem of slow sedimentation,this article chooses the combination of polyaluminum chloride（PAC）and polyacrylamide（PAM）,which can significantly accelerate the sedimentation speed of the wastewater.Through single factor and orthogonal experiments,it is found that the significant degree of factors affecting the sedimentation rate of experimental wastewater is:PAM dosage>PAC dosage>stirring time.