I have chloride solution of Sn where Pb is an impurity having concentration of 950-990 mg/L. I would like to remove Pb before electrorefining of Sn. While trying with BaCO3, there was about 20-25% Pb removed from the solution. It is possible to use any other chemical that can remove Pb more than 60% at a time? Could anybody tell if BaSO4 be more effective than BaCO3? Thank you.
Dear Mr Mishra, there are some possibilities. The solubility product of the lead compounds can give us an idea. Lead (II) carbonate presents a value equal to 7.40x10-14. Others compounds are: Lead(II) hydroxide: 1.43×10-20; Lead(II) iodate: 3.69×10-13; Lead(II) sulfate: 2.53×10-8; Lead(II) sulfide: 3×10-28.
Low solubility product means that the compound is few soluble in water. In your case, I think that lead (II) sulfide is the product that you need generate. You can use sulfidric gás (but is toxic, be carefull) or tioacetamide. The solubility product of lead (II) sulfate is higher than lead (II) sulfide, therefore barium sulfate is not the best choice. Besides, the addition of another cation (barium, for example) can contaminate your solution and be difficult eliminate it. Well, this is a suggestion, maybe it work. I hope that this help you.
Thanks Julio for your kind reply. At present I cannot use sulfidic gas as it is industrial process and it would be harmful for the workers. I have to think the alternate one. In sulfate base it is easier to precipitate Pb than chloride base. PbSO4 has lower solubility product than PbCl2. I tried with BaCO3, but Ba did not show any contamination in Sn metal preparation. But I am concenred about incomplete removal of Pb, which comes with Sn metal during electro-refining process, decreases the purity of metal. If you come across any article please let me know.
Thanks and regards.
Dear Mr Mishra, could you use tioacetamide as source of sulfide? Tioacetamide is less harmful than sulfidric gás. But your process is industrial, the cost shall be high. Lead (II) carbonate is less soluble than lead (II) sulfate. Therefore, to use carbonate or carbonic gas must be better than sulfate. Maybe happened some changing at pH. You could use a complexing agent as EDTA. This changes the electrical potential of the electro-refining of tin. I don't know, are just suggestions. I will try search some paper about the subject. If I find, I will send for you. Best regards, and good luck.
Dear Mr Mishra, follow some links that contain articles about subject.
1) http://www.isca.in/rjrs/archive/v1i10/1.ISCA-RJRS-2012-127.pdf (This article describes thermodynamic conditions, pH, electrochemiacal potential, ionic strength, ...);
2) http://www.tandfonline.com/doi/abs/10.1081/SS-100106110?journalCode=lsst20#preview;
3) http://www.scielo.br/scielo.php?pid=s1517-70762007000300011&script=sci_arttext.
Some uses sodium sulfide and explain the best ratio between lead (II) and the others metal for eficiente separation. You can download them. I hope sucess. Best regards.
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