China Nonferrous Metallurgy

The traditional process for lead anode slime includes reduction smelting to produce lead containing precious metals, oxidation refining to produce silver anode plate, and electrolysis refining to produce silver powder. During the process, the antimony element basically enters the flue dust in the form of Sb2O3 and As2O3, from which antimony is recovered by pressure leaching process. The whole process has some shortcomings such as long process, high cost, low recovery rate, and the large amount of waste water is produced, which is neither economical nor environmentally friendly. In this paper, industrial sodium hydroxide was added to the converter during the reduction smelting process to efficiently remove the arsenic in lead anode slime. In the process, arsenic is separated in the form of arsenic alkali residue from precious lead, and the precious metals are recovered by vacuum distillation technology. The verification test results show that the arsenic removal rate can reach more than 95% under the conditions of 2〖DK〗〖DK〗∶1 mass ratio of sodium hydroxide to arsenic content in precious lead alloy, reaction time 4h and reaction temperature 1100℃. Combined with vacuum distillation technology, the recovery rate of gold, silver, bismuth and antimony is improved, and the process is shortened, and the production of antimony slag, soot and wastewater is reduced. It not only saves the smelting cost, but also reduces the pressure of environmental protection, and has good demonstration effect and popularization value.