| High purity quartz sand is widely used in semiconductor,solar energy,aerospace,optical fiber communication and other high-end fields,which is a strategic resource urgently needed by the country.Photovoltaic industry is a sunrise industry based on semiconductor technology and new energy demand,which is the highest point of global advanced industry competition in the future.Impurities Al and Fe in quartz ore are harmful elements,which need to be removed efficiently in the process of purification.The presence of gas-liquid inclusions in quartz will produce bubbles in quartz products and affect product quality.In order to achieve the efficient removal of impurities Al,Fe,and gas-liquid inclusions,this paper proposes a new idea for the preparation of high-purity quartz sand,and carries out the following research contents:（1）TG-DSC was used to analyze the temperature of phase transformation during the heating process of vein quartz,and X-ray diffraction was used to analyze the crystal structure of calcined and quenched quartz sand.Rietveld finishing method was used to calculate the crystal structure content of quartz at different temperatures,and the effect of crystal form content of quartz on the removal of Fe and Al was studied.The experimental results show that:The initial crystal form of natural vein quartz used in this experiment isα-quartz.After roasting,the crystal form changes.At 900°C,the content ofα-quartz was 4.92%,the content ofβ-quartz increased to 94.67%.After pressure leaching,the content of Fe decreased from 220×10-6 to 2.8×10-6,the removal rate was 98.73%,the content of impurity al decreased from 180×10-6 to 14.7×10-6,and the removal rate was 91.27%.At this time,the content of Al has reached the standard of photovoltaic quartz sand.（2）In order to further reduce the content of Al and Fe,the combination of ultrasonic enhanced leaching and chlorination leaching was used.Sodium carbonate had a good binding effect on the impurity Al in quartz sand,and potassium chloride could be removed by fully reacting with impurities in quartz lattice.The experimental results show that:When the ultrasonic power is 200W,the leaching time was 30min and the concentration of sodium carbonate is 4g/L,the removal rates of Al and Fe reach equilibrium,and the removal rates of Al and Fe reach 92.11%and 98.80%.The contents of Al and Fe are 14.20×10-6 and 2.64×10-6respectively.The results show that the removal rates of Al and Fe are 92.22%and 98.82%respectively under the conditions of 2 wt.%KCl solution,2 h leaching time and 5:1 liquid-solid ratio.The contents of Al and Fe are 14×10-6 and 2.58×10-6 respectively.（3）Quartz sand was treated by microwave strengthening roasting and high temperature sulfuric acid roasting.Because quartz contains gas-liquid inclusions,microwave has the characteristics of selective heating,which can make the gas-liquid inclusions rapidly rise temperature,burst them,crack occurs at the interface of the gas-liquid inclusions,and make acid enter into a better chemical reaction.The content of water molecules and light transmittance of quartz sand gas-liquid inclusion were determined by Fourier transform infrared spectrometer and721 spectrophotometer.The experimental results show that when the microwave roasting temperature is 900°C,the roasting time is 1h,the sulfuric acid concentration is 6mol/L,the liquid-solid ratio is 8:1,the sulfation roasting temperature is 150°C and the roasting time is 2h,the infrared absorption peak intensity and area of water molecules in quartz sand are the smallest,the light transmittance is 74%,and the inclusions in quartz sand are effectively removed. |
PDF Full Text Request