| With the rapid development of high-tech industries such as solar energy,optical fiber communication and aerospace technology,the quality and demand of high-purity quartz are all put forward higher requirements.This study of high-purity quartz production by quartz veins resource in our country is of great signifinace.In this paper,the quartz from Qichun was purifiedby mineralogy analysis,calcination,constant/hot pressure leaching and magnetic separation,and the relevant mechanism in leaching process was discussed.The process mineralogy analysis showed that the mass fraction of SiO2 in the quartz sand ore was 99.95%,the main types of mineral impurities included muscovite,rock salt,calcium salt and some iron-containing oxides,the total amount of impurities was 457.798?g/g,and the main impurity metal element were as follows??g/g?:Al260.5?Fe 57.76?Mg 13.7?K 83.85?Na 13.22?Ca 14.44.The results of single acid leaching tests at atmospheric pressure show that HF is better than HCl.The mixed acid leaching tests show that HCl can catalyze the reaction of HF with impurity metal elements.Compared with single acid leaching,the removal rate of Al,Fe and the total impurity elements are effectively improved with lower HF consumption.For two main impurity elements Al and Fe,reduction leaching better than the oxidation leaching and consume fewer reagents at the same time.In the conditions of atmospheric leaching,setting stirring rate 200r/min,leaching temperature 80?,liquid-solid ratio 10:1,after leaching 12h.The total impurity elements reduced to 86.56?g/g,the total removal rate reached 81.09%,and the mass fraction of SiO2 reached 99.989%.Using the hot pressing process to enhance the purification effect and reduce the amount of acid,the results of orthogonal experiment in hot acid leaching showed that the influence of HF on the removal rate of metal elements was the most obvious,followed by HCl and C2H2O4.As the pressure and temperature rised in the hot pressing conditions,chemical reaction rate accelerated,reaction time shortened,and the energy will break the reaction energy barrier enhance the removal of alkali metals.Setting leaching temperature at 180?,liquid-solid ratio at 4:1.After leaching for 5h,the total impurity elements reduced to 46.73?g/g,the total removal rate reached89.79%,the mass fraction of SiO2 reached 99.994%.High temperature vacuum calcination can effectively reduce the content of some alkali metals,the removal rate of impurity element get better when high temperature calcination was used before acid leaching,because the dilatation coefficient between quartz and the impurity minerals are different,during the heating and cooling process,in the area of the mineral inclusions concentrated get further rupture and make it exposed to the surface,then facilitates the contact and removal of mixed acid leachate with impurity metal elements.Leaching at 180?for 5h after calcination at 1500?for 5h,the total amount of impurity elements decreased to 38.06?g/g and the total removal rate reached 91.69%,the mass fraction of SiO2 reached 99.995%Study on the kinetic of leaching process with the respresent of Al showed that removal of Al from quartz sand in leaching process belong to the internal diffusion control model.At normal pressure leaching,the removal rate is controlled by the chemical reaction and the apparent activation energy of Al is 21.78kJ·moL-1.At hot pressure leaching,the removal rate is controlled by the chemical reaction and the apparent activation energy of Al is 22.01kJ·moL-1.The results of particle size and morphology testing analysis show that the process of leaching and high temperature calcination will destroy a part of the quartz structure,produce some large cracks and reduce average particle size,which is beneficial to the leaching process and improve the removal rate of impurity elements,while the impact of the overall size of quartz sand is small,and will not affect the use of industrial. |
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