Complex Lead Dust Wet Processing Of New Technology Research,

A whole-wet technology treating the washing residue of a certain complex dust & smoke containing lead to comprehensively recover the valuable metals such as Pb, Bi, Sn, Ag and In by two-step method was described, where lead product met the criterion of industrial secondary category, bismuth products met the requirement of analytic purity, impurity content of ammonium chlorostannate was less than 0.1%, Ge, In and Ag were well enriched. All these show that this technology lays a good basis for the next recovery of the above valuable elements.The experimental process mainly includes transformation, leaching lead and preparing lead products, CR, preparing bismuth products, recovering tin and preparing tin products and treating the transformed liquor. During transforming process, because solubility of PbCO₃ is less than that of PbSO₄, SO₄²- ion can be effectively removed by PbSO₄ transforming into PbCO₃. For leaching lead and preparing lead products process, lead and a small quantity of bismuth enter solution in the form of nitrate, the latter is removed by neutralization precipitation method, the former is precipitated from Pb(NO₃)₂ to PbSO₄ accompanied with regeneration of nitric acid, and then PbSO₄ is washed and neutralized by caustic soda to produce tribasic lead sulfate or lead oxide. During CR process, thecarbonates and oxides of Bi, As, Sn, Cu, Zn are dissolved by HC1, meanwhile arsenate is reduced and dissolved. At 100¹25°C, low boiling point AsCl3> GeCU^ SnCL^ and HC1 are respectively distilled, and then Ge and As are precipitated by Na2S and HC1 is regenerated. During preparing bismuth products, B1CI3 solution is neutralized and hydrolyzed by NH3-H2O to produce preliminary bismuth chloro-oxide, which is firstly washed with nitric acid to remove impurities, and with sulfur acid to remove Cu, Sn, Zn and Fe, and then neutralized by alkali to remove SO42' ion and alkali dissolvable impurities such as Sn, As, Se and Te. The preliminary bismuth chloro-oxide is dissolved into Bi(NO3)2 by a certain concentration of nitric acid, and then Bi(NC>3)2 is firstly transformed into bismuth sub-nitrate by NH3#H2O neutralization method, and then bismuth sub-carbonate by adding ammonium carbonate. The bismuth sub-nitrate or bismuth sub-carbonate is changed into bismuth oxide by roasting. For recovering tin and preparing tin products process, tin entering bismuth leaching solution is separated with bismuth in the form of NFLjSnCLj product, and tin in leaching residue produces Pb-Sn alloy with Pb during reduction smelting process, which is oxidized and changed into preliminary NaSnO2 by alkali smelting process. During treating the transformed liquor process, Cu and Cd can be removed by sulfuration precipitation method because solubilities ofCuS and CdS are less than ZnS. As5+ is combined with Mg and removed in the form of undissolvable arsenate. During distilling ammonium process, (NH4) 2CO3 is decomposed into NH3, which is absorbed by cooling water and partly escaped. When PH=2.5³, zinc ammonium salt is produced.The direct recoveries of Pb, Bi and Sn are 93.55 %, 92.13 % and 90.36%, respectively. And the total recoveries of Pb, Bi, Sn, In and Ag are 97.76%, 96.22%, 96.13%, 89.35% and 90.71%, respectively.The experimental results show that the technology can comprehensively recovery the nine elements of Bi, Pb, Sn, Cu, Zn, Cd, In,Ag and Ge, which have high direct recovery and total recovery, and solve the environmental pollution problem.