Chloridizing Roasting of Bismuthinite with Sodium Chloride-Oxygen

摘要

Chloridizing roasting of bismuthinite (Bi_2S_3) with NaCl-O_2 has been studied to remove the impurity Bi by volatilization from copper concentrates that contain bismuthinite. The study was conducted using mixtures of Bi_2S_3 and NaCl in a horizontal furnace and TGA apparatus. The variables were temperature, oxygen partial pressure, and NaCl concentration. The chlorination was analyzed by weight loss measurement method. XRD results of calcines reacted for short times in 21% O_2, and 850-1000 ℃ showed the presence of Bi, BiOCl, and Na_2SO_4, while at longer times in the same conditions, Bi_2O_3 was identified as a stable phase. Thus, the chloridizing-volatilization of Bi_2S_3 proceeds through the formation of Bi and BiOCl. Temperature affected significantly the fraction of weight loss of samples. At 600 and 900 ℃ in 10.3% oxygen, the maximum weight loss was 4 and 20%, respectively. An increment in the partial pressure of oxygen in the range 1-21% affected negatively the Bi_2S_3 conversion. At normal roasting temperatures (550-700 ℃), bismuth volatilization by NaCl roasting was found to be marginal.