Metal recovery

1. A method for recovering tin and/or tin alloy from a substrate comprising:

providing a substrate having tin and/or tin alloy thereon;

contacting the tin and/or tin alloy with a stripping solution consisting essentially of an inorganic acid and a persulfate compound;

adding a flocculant to the stripping solution;

recovering tin salt and/or tin alloy salt precipitated from the stripping solution; and

recovering tin and/or tin alloy from the tin salt and/or tin alloy salt, respectively,

wherein the inorganic acid is selected from sulfuric acid, hydrochloric acid and alkane sulfonic acid; and

wherein the persulfate compound is selected from ammonium persulfate, sodium

persulfate, barium persulfate, lithium persulfate and combinations of two or more thereof; and

wherein the persulfate compound is present in a concentration from about 100 to about 500 g/l.

2. The method of claim 1 , wherein the substrate comprises copper and/or copper alloy.

3. The method of claim 1 , wherein the tin and/or tin alloy is recovered from the tin salt and/or tin alloy salt by smelting.

4. The method of claim 1 wherein the substrate is part of a photovoltaic interconnection ribbon, busbar, or electronic waste.

5. The method of claim 1 wherein the tin and/or tin alloy is contacted with the stripping solution for at least about 1 minute.

6. The method of claim 1 wherein the tin salt and/or tin alloy salt is recovered from the stripping solution by filtration or centrifugation.

7. The method of claim 1 wherein the concentration of the inorganic acid is between about 10 to about 500 g/l.

8. The method of claim 1 wherein the stripping solution further consists essentially of one or more of imidazole, pyridine, triazine, triazole and derivatives thereof.

9. The method of claim 8 wherein the triazole derivative is benzotriazole and benzotriazole is present in the stripping solution from about 0.1 to about 10 g/l.

10. The method of claim 1 wherein the stripping solution further consists essentially of a surfactant.

11. The method according to claim 10 , wherein the stripping solution consists essentially of:

10 g/L to 500 g/L an inorganic acid selected from sulfuric acid, hydrochloric acid and alkane sulfonic acid;

100 g/L to 500 g/L of a persulfate compound selected from ammonium persulfate, sodium persulfate, barium persulfate, lithium persulfate and combinations of two or more thereof;

0.1 g/L to 10 g/L benzotriazole; and

2.0 wt. % of less of a surfactant.

12. The method of claim 1 wherein contacting the tin and/or tin alloy with a stripping solution comprises immersing the tin and/or tin alloy in the stripping solution.

13. The method of claim 1 wherein the solution further consists essentially of an aqueous solvent.

14. The method of claim 1 wherein the method is a batch method and the method further comprises re-cycling the stripping solution between batches.

15. The method according to claim 1 , wherein the method for recovering tin and/or tin alloy does not require subsequent electrowinning and/or a pH precipitation step.

16. A method of removing tin and/or tin alloy from a copper substrate comprising:

providing a copper substrate having tin and/or tin alloy thereon; and

contacting the tin and/or tin alloy with a stripping solution consisting essentially of an inorganic acid and a persulfate compound,

wherein the inorganic acid is selected from sulfuric acid, hydrochloric acid and alkane sulfonic acid; and

wherein the persulfate compound is selected from ammonium persulfate, sodium persulfate, barium persulfate, lithium persulfate and combinations of two or more thereof; and

adding a flocculant to the stripping solution.

17. The method of claim 16 further comprising recovering the copper substrate from the stripping solution.