The Study of Separation of Silicon and Silicon Carbideby Electrophoresis and Gravity.

• Main Authors: Po-Han Huang, 黃柏涵
• Other Authors: Shi-Chern Yen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/47700874762833605822

碩士 === 國立臺灣大學 === 化學工程學研究所 === 95 === Solar grade silicon material is important in the manufacturing of photovoltaic cells. There is about 34% kerf silicon loss during Si wafer slicing process. The slurry wastes include abrasive particles (SiC), lubricating oil (ethylene glycol), metals from cutting wire, and the kerf silicon fine particles. The recycle of the silicon from the cutting slurry could save the raw material used significantly. In the first part, we treat the slurry with acid washed, and determine the amount of metal content. At the same time, we observe the change of metal content in different condition of acid washing. And decide the best condition to remove the most metal component from slurry. In this thesis, we try to remove the metal component utilizing the nitric acid (HNO3), when the concentration of the acid is greater than 0.5M, the volume ratio of acid and slurry is great than 23, and mixing time over 40 minutes, we can remove 99.5 wt% of metal in slurry. In the second part, we separate the SiC from Si particles by Electrophoresis and Gravity force. We get the dry solid component after acid washing, and dilute the dry solid by water. We inject the diluted solution into the settling tank by metering pump. When particles settle in the tank, we apply the electric field in the solution. Finally, we discuss the effect on the separation in different pH value of diluted solution and different electric field strength in solution. In this thesis, we use the solution which the pH value is 7, the ionic strength is less than 0.005M, and also we apply the voltage 5V to the solution. We can increase the silicon content in slurry from 25wt% to 80wt% by the electrophoresis and gravity effect.