Abstract:

Based on the analysis of research progress in drained slurry and white carbon black，the preparation of white carbon black using silicon as starting material is proposed. The reaction of ammonium fluoride with silicon contained in the drained slurry generated by cutting silicon crystal using a wire-saw，the amination reaction of ammonium fluorosilicate，as well as the recycling of ammonium fluoride in the closed cycle system are investigated. Results showed that the recovering of ammonium fluoride is higher than 95% and the optimum conditions are: mass concentration of ammonium fluoride is 40%—55% and temperature is 50—60℃ for the reaction ammonium fluoride with the drained slurry. While for the amination reaction，the pH value is no higher than 6.9 in the nucleation stage and 7.1 in the growth stage，the mass concentration of ammonium fluorosilicate is 12% with two stages of precipitation and filtration，the dropping rate of ammonia water is 2 drop/s at the initial precipitation stage and 0.5—1 drop/s at the second precipitation stage and temperature is 40—50 ℃. This process has the advantages of diversity in starting material，low temperature，low-loss of ammonium fluoride and low-cost for reclaiming silicon from drained slurry.