Study On Preparation Of SbCl₃and Sb₂O₃from Lead Anode Slime Bearing High Antimony

In this paper, the traditional treatment status of jamesonite, lead anode slime bearing high antimony and low silver and preparation of Cubic antimony white have been general summarized. The technology of preparing cubic antimony white from lead anode slime bearing high antimony and low silver by potential-controlled chloridization leaching, distilling concentration and continuous distillation has been proposed.The relationship of [Pb2+][Cl-]2-lg[Cl]T, E-lg[Cl]T in Pb-Sb-Cl-H2O system were studied and the solubility of lead chloride at different antimony concentrations was calculated both based on principle of simultaneous equilibrium. The results showed that insoluble salt PbCl2would only exist stably in a certain concentration range of chlorine ion. The solubility of Pb2+in the solution decreases with increasing of the concentration of antimony in the system, whereas increases with increasing of the concentration of total chlorine. The concentration range of total chlorine causing lead solubility less than0.005mol/L is ever-expanding. This concentration range of chlorine ion expands a little with increasing of the concentration of antimony in the system while narrows as the system acidity increases.Similarly, insoluble salt AgCl only stably exist at a certain concentration range of chloride ions. When the concentration of Sb in the system continuously increased, this concentration range of chlorine ion in which insoluble salt PbCl2existed stably expanded, but the solubility of Ag in the solution decreased. And the concentration range of total chlorine expanded continually corresponding solubility of silver less than0.00001mol/L, which meant separating the Ag and Sb was feasible. These study provided a theoretical basis for the separation of lead and antimony, silver and antimony in Sb-Cl-H2O system. As a result, the feasibility and an efficient way for separating these two kinds of metals were discussed and indicated, respectively.The technology of preparing cubic antimony white from lead anode slime bearing high antimony and low silver by Potential-controlled chloridization leaching and continuous distillation was studied in detail. Experimental results were showed as following.1. The removal ratio of silicofluoric ion in leaching solution is about91%by the addition of NaCl. Si and F in leach liquor can be further removed when distillation temperature is120℃by distilling concentration.2. The solution potential in the process of leaching process includes three stages:In the first stage, the solution potential increases slowly; In the second stage, there are no obvious change in the solution potential, so a plateau emerges in the potential-time curve; In the third process, the solution potential increases greatly. The length of plateau in the second stage decreases with increasing the concentration of Sb3+or the temperature. The phase of leached residue is determined by the solution potential. When the solution potential is controlled greater than430mV, there is mainly AgCl and PbCl2existed in the leached residue, when the potential is controlled under380mV, the metal Sb is also existed in the leaching residuum besides the AgCl and PbCl2. Therefore, the optimum potential of solution is430mV, the leaching rates of Sb, Bi and Cu are greater than98%, the leaching rate of Pb and Ag are3.10%and2.34%respectively.3. In the chloridization leaching process, Sb5+was reduced with lead anode slime at80℃for two hours, then the content of Sb5+is only0.60g/dm3in the reduced solution. At the same time, Sb2O3in lead anode slime was dissolved by hydrochloric acid in chloridization leaching solution, the content of Sb in the reduced solution will increase. Using, silicon compound can be distilled out basically with distilling concentration, when the reduced solution is heated to120℃. The removal of silicon compound is beneficial to the subsequent continuous distillation; it can solve the problem of pipe plug brought out because of the crystallization of these substances during the evaporation and cooling process. The major component of crystallization is amorphous hydrated silicon dioxide at the distilling concentration process. And the major components of cooling and crystallizing are AgCl and PbCl in the distillation mother solution, and solubility of AgCl and PbCl are decreased when the distillation mother solution is cooled at the atmosphere. So it can be recycled due to the high degree of enrichment.4. Production capacity of the continuous distillation is depended on distillation speed. Distillation speed gradually increases with the increasing of distillation negative pressure, and it will decrease with the increasing of distillation temperature. The distillation ratio of As increases with the increasing the first step distillation temperature. Arsenic distillation ratio is more than70%at130℃, but arsenic distillation ratio is still less than90%at130℃. The quantity of distilled arsenic is the most at the rage of135℃to150℃, so arsenic distillation ratio is only95.2%at180℃. Purity of trichloride antimony is up to99.94%at the second step distillation. The content of impurity in the trichloride antimony is lower, The SbCl3reach the level of the reagent completely, the distillation ratio of trichloride antimony is more than99.0%.5. pH decreases slowly when ammonium tartrate exists in the neutralized transformation solution. But it decreases fast when there is EDTA in the neutralized transformation solution. When tartrate ion exists in the neutralized transformation solution, antimony chloride was transformed into single cubic antimony white. And when EDTA exists in the neutralized transformation solution, antimony chloride is transformed into rhombic antimony white. When n(Sb):n(C4H4O62-)=30:1, the product presents a octahedron structure and its edges and corners are clearly. The whiteness and component of antimony white are all up to the national product standard.6. The residue bearing Pb and Ag was transformed into by carbonate, then lead in the transformed residue was leached with silicofluoric acid, and Silver was leached with ammonia, finally silver powder was recovered while silver ion was reducer by hydrazine hydrate. The recover ratio and overall recover ratio of silver are97%and98.12%, respectively. Lead was recovered to return to the electrowin system with lead fluosilicate. The recover ratio and overall recover ratio of lead are86.26%and99.12%, respectively.The distillation residue is soaked by hydrochloric acid. The soak solution will be hydrolyzed to recover Sb and Bi by step. The soak solution was hydrolyzed by adding water, the precipitation of Sb4O5Cl2was returned to the leaching system. pH of the hydrolyzed mother solution was adjusted by using ammonia to obtain BiOC1. Moreover, copper powder is recovered from neutralizing hydrolysis mother solution with replacement of iron powder. This process was feasible and the valuable metals, such as copper, antimony and bismuth can be recovered. The recovery rates of the valuable metals are more than95%separately.7. The recover rate of Sb is up to98%in the process of preparing antimony white from lead anode slime bearing high antimony and low silver. The experiment result was reappear well. Co-existed metals, such as Pb, Ag, was distributed in the leached residue, the crystallized product of cooling reducing solution and the distillation residue mostly, the sum of above all reach100%.99.04%of Bi,98.16%of Cu in the anode slime were enriched in the distillation residue respectively. And90.42%of As in the anode slime was enriched in the continuous distillate. It needs to considerate economically and reasonably that the relationship between concentrations of HC1which is recovered from dilutes hydrochloric acid and concentration of HC1as a leach solution into the leaching process.