高铋铅阳极泥碱性氧化浸出渣熔炼-电解提铋研究

Research on bismuth extraction from alkaline oxidative leaching residues of bismuth-rich lead anode slime by casting and electrolysis

以高铋铅阳极泥碱性氧化浸出渣为原料,采用碳热还原熔炼-电解工艺提取铋,同时富集金银.热力学分析表明金属碳热还原的初始温度由低到高依次为:铜、铋、铅、锑、锡;铋氧化物在800℃以上可获得足够大的还原热力学推动力.熔炼粗铋合金的最佳温度为800℃,碳用量为浸出渣质量的5%,四硼酸钠用量为浸出渣质量的15%,熔炼时间为1.5 h.在此条件下,粗铋合金中铋、金、银的平均含量分别为84.29%,39.62 g/t和6 519 g/t,相比于铅阳极泥原料,金银分别被富集1.8倍.采用公斤级粗铋合金板为阳极,在BiCl_3-NaCl-HCl体系中分别电解24 h、48 h、72 h、112 h,阴极产物中铋平均含量>98%,电流效率>96%,铋电解阳极泥中金、银平均含量分别为222.94 g/t,34 287.6 g/t,相比铅阳极泥原料,金银平均被富集到9.54倍和10.13倍.

Alkaline oxidative leaching residues of bismuth-rich lead anode slime were adopted to extract bismuth and enrich gold and silver by using carbothermal reduction casting and electrolysis process.Thermodynamics analysis indicates that the initial carbothermal reduction temperature of metal oxides from low to high are Cu,Bi,Pb,Sb,Sn.Bismuth oxides can obtain enough reduction thermodynamic driving force when the temperature excesses 800℃.The optimum technical conditions are as follows:temperature,800℃;carbon addition,5%of the mass of leaching residue;Na2B4O7 addition,15%of the mass of the leaching residue;time duration,1.5 h.Under such conditions the average contents of bismuth,gold and silver were 84.29%,39.62 g/t and 6519 g/t,respectively.Compared with the raw lead anode slime,the content of gold and silver were enriched 1.8 times respectively.Kilogram-scale crude bismuth alloys were electrolyzed in HCl-NaCl-BiCl3 system as anodic plates for 24 h,48 h,72 h,112 h.The results indicated that the content of bismuth in the cathodal products exceeded 98%,the current efficiency,96%,and the average content of gold and silver content were 222.94 g/t,34287.6 g/t,respectively.Compared with the raw lead anode slime,the content of gold and silver were enriched 9.54 times and 10.13 times,respectively.