Chemical Cracking Effect of Aqua Regia on the Purification of Metallurgical-Grade Silicon

Abstract

The chemical cracking effect on metallurgical-grade silicon (MG-Si) during leaching by aqua regia was investigated. The results showed that the granularity of the particles was reduced by acid leaching, and the phenomenon was more noticeable with the increase in the silicon particle size. The cracking was essentially ascribed to the dissolution of the major impurities that depended on the composition and distribution of the impurity phases in MG-Si. In addition, the removal efficiency of the main metallic impurities with the occurrence of the chemical cracking effect during the leaching process was studied. The remarkable removal efficiency was obtained from the coarse particle size, where 79% Fe, 77% Al, 45% Ca, and 63% Ti were removed. The reason could be attributed to the strong oxidation of aqua regia that promoted the dissolution of the Si− Al−Fe soluble phase, which resulted in the enhanced removal effect of acid on the impurities.

Enhancement in extraction of boron and phosphorus from metallurgical grade silicon by copper alloying and aqua regia leaching

“…For MG-Si, research results indicated that more friable phases containing impurities were concentrated in the finer fraction of particles during sieving. It is found that these could not be so easily removed by acid leaching (Zhang et al, 2013).…”

Mechanism of Carbon Removal from Crude Metallurgical Grade Silicon during Oxidation Refining

“…3. HCl [6, 19, 21, 30-32, 34, 35] Al, Ca Fe, Ti, V HNO 3 [6,31,32] Al, Ca Fe, Ti, V HCl+HF [8,9,30,31,36,37] Al, Ca, Fe, Ti, V Al, Ca (when the HF concentration is too high) HNO 3 +HF [30,31,33] All elements -Aqua regia [7,30,31] A l , C a , F e T i , V…”

“…The segregation coefficient of metal impurities is less than 1 × 10 −3 , and a strong segregation phenomenon is observed in the solidification process [5]. Acid leaching [6][7][8][9], and directional solidification [10,11,12,13] can effectively separate metal impurities from MG-Si. The segregation coefficient of non-metallic impurities is generally greater than 0.01, and the segregation phenomena of these impurities are not significant in the solidification process, limiting the deep purification of MG-Si [5].…”

Effects of Slag Refining on Boron Removal from Metallurgical- Grade Silicon Using Recycled Slag with Active Component

“…At elevated temperature, the reaction rate of oxidation and chlorination is high, so the chemical reaction is commonly ignored [24,25], therefore, the rate-limiting steps is usually determined by the mass transfer and evaporation process as step (1), step (3) and step (5). The k t has been calculated in 4.1, the results indicate that the mass transfer steps will limit the total reaction rate.…”

“…In the industrial area, metallurgical refining way combines a series of progresses: slag refining [4], acid leaching [5,6], vacuum refining [7], electron beam refining [8] and directional solidification.…”