I know that clay adsorbs heavy metals such as lead. How can I pull the lead back off of the clay so that it will percipitate with KI?

To pull the lead back off of the clay so that it can precipitate with KI (potassium iodide), you can follow these steps:

1. Prepare a solution of KI: Dissolve a known amount of KI in distilled water. The concentration of KI will depend on the amount of lead you expect to recover, so the specific concentration may vary.

2. Add the clay containing the adsorbed lead to the KI solution. Make sure the clay is thoroughly mixed with the solution to allow the lead to react with the KI.

3. Stir the mixture: Gently stir the mixture, ensuring that all clay particles come into contact with the KI solution. This allows the lead ions adsorbed to the clay to react with the iodide ions from the KI solution.

4. Wait for the precipitation: After stirring, allow the mixture to sit undisturbed for some time. The lead present will react with iodide ions to form a yellow precipitate known as lead iodide (PbI2). The time required for the precipitation to occur may vary depending on factors such as the amount of lead present and the concentration of the KI solution.

5. Filter and collect the precipitate: Once the lead iodide has formed, carefully filter the solution to separate the precipitate from the now lead-free solution. Use filter paper or any suitable filtration method to collect the solid lead iodide.

6. Wash and dry the precipitate: Wash the collected lead iodide with distilled water to remove any impurities. After washing, allow the precipitate to dry completely, either by air drying or using gentle heat.

By following these steps, you should be able to recover the lead from the clay as lead iodide, which can then be further processed or studied as needed.