Using Citric acid/sulphamic acid mixed with NaCl and O2 for base metals

[Chirou]

What are you trying to accomplish with this experiment?
You certainly are creating a lot of waste.
I would go with AP, less hassle, less waste and less time needed.

Dissolving copper to free Gold foils using only what i have available, also most of it i get for free both chemicals and materials. Only think i got unlimited is time.
Waste is welcome some will go to geology students to grow Crystals, some to our students to be turned back into copper and tested under microscope to see crystal latices etc

 

[Alondro]

PbSO4 and PbCl2 are not soluble. If you have lead in your material (especially old e-waste manufactured earlier than 2000) - it cannot be leached by hydrochloric or sulfuric acid and will remain in your material.

At subsequent stages of processing, for example with nitric acid, you will get much more toxic and carcinogenic lead nitrate.

Any heavy metals organic complexes are relatively dangerous and shouldn't be inhaled or eaten. But if you need to remove lead - citric acid is the best way (much better than acetic acid).

Lead (II) chloride is not completely insoluble. Approximately 10g/L will dissolve in aqueous solutions. It is TOTALLY soluble in concentrated HCl, which is often the reason people think they suddenly have silver chloride when they dilute or neutralize their base metal-saturated HCl waste from old electronics, and a white goo suddenly appears. When the pH rises to about 2, if large amounts of Pb(II)Cl2 are present, it will begin to precipitate.

Low concentrations, however, will remain in solution. This is why we add sulfuric acid to the gold-bearing solutions and cool the solution. There will always be some lead chloride floating around UNTIL it is dropped as lead sulfate, which IS for all intents and purposes insoluble in many conditions (only 0.4g will dissolve in a liter of water at room temp. Cool it to 10C or lower, and only 0.03g/L will dissolve), with it being soluble only in ammonia and ammonium salt solutions.

 

[orvi]

Lead (II) chloride is not completely insoluble. Approximately 10g/L will dissolve in aqueous solutions. It is TOTALLY soluble in concentrated HCl, which is often the reason people think they suddenly have silver chloride when they dilute or neutralize their base metal-saturated HCl waste from old electronics, and a white goo suddenly appears. When the pH rises to about 2, if large amounts of Pb(II)Cl2 are present, it will begin to precipitate.

Low concentrations, however, will remain in solution. This is why we add sulfuric acid to the gold-bearing solutions and cool the solution. There will always be some lead chloride floating around UNTIL it is dropped as lead sulfate, which IS for all intents and purposes insoluble in many conditions (only 0.4g will dissolve in a liter of water at room temp. Cool it to 10C or lower, and only 0.03g/L will dissolve), with it being soluble only in ammonia and ammonium salt solutions.

Yup, agreed. Worked with lots of lead containing materials and PbCl2 is certainly soluble in chloride solutions. Very common thing is that you have lead in chloride solution with gold, and want to lower the solubility of AgCl in it by dilution - this can cause not only AgCl to precipitate, but in majority of cases also lead chloride. Latter often needs some time to fully came out of solution and it can be later found mixed with gold as needle like crystals. Similar behaviour is observed also with calcium sulfate - which can form in solution, if you leached whole components or boards/connectors (calcium carbonate is often used as filler). Then you denox with sulfamic, which in turn create sulfuric acid (or directly add sulfuric to remove lead) and CaSO4 will slowly form.

With lead sulfate lead elimination, it is not that straightforward as we are usually thinking. Often, we use solubility data for pure water - which is not correct, since we mostly deal with heavy chloride and nitrate solutions. In these, PbSO4 has higher solubility. Try to add 1g of dissolved lead into some heavy chloride or nitrate solution and then add sulfuric acid to precipitate it. Weighing precipitate obtained will tell you how much is left in solution - and it is many times quite significant number.

 

[Alondro]

Yup, agreed. Worked with lots of lead containing materials and PbCl2 is certainly soluble in chloride solutions. Very common thing is that you have lead in chloride solution with gold, and want to lower the solubility of AgCl in it by dilution - this can cause not only AgCl to precipitate, but in majority of cases also lead chloride. Latter often needs some time to fully came out of solution and it can be later found mixed with gold as needle like crystals. Similar behaviour is observed also with calcium sulfate - which can form in solution, if you leached whole components or boards/connectors (calcium carbonate is often used as filler). Then you denox with sulfamic, which in turn create sulfuric acid (or directly add sulfuric to remove lead) and CaSO4 will slowly form.

With lead sulfate lead elimination, it is not that straightforward as we are usually thinking. Often, we use solubility data for pure water - which is not correct, since we mostly deal with heavy chloride and nitrate solutions. In these, PbSO4 has higher solubility. Try to add 1g of dissolved lead into some heavy chloride or nitrate solution and then add sulfuric acid to precipitate it. Weighing precipitate obtained will tell you how much is left in solution - and it is many times quite significant number.

I take advantage of that small solubility when removing the precipitate, which is often very fine, from my initial solutions of dissolved gold foils with HCl and bleach. Heating and cooling several times causes the initially very fine lead chloride powder to flocculate and grow into larger crystals, which are much easier to filter.