The dark blue solution formed when copper dissolves in nitric acid is copper(II) nitrate (also called cupric nitrate).
Putting an iron bar into a copper(II) nitrate solution will drop solid copper metal out of the liquid and replace it with iron nitrate via a single-displacement reaction.
To safely clean up the liquid and recover the copper after using the iron bar, you must neutralize any remaining acid, filter out the solids, and cement the leftover heavy metals.Do not pour the remaining liquid down the drain, as it contains dissolved iron and potentially toxic leftover copper ions.
Separate the MetalsScrape the Copper: Pull the iron bar out of the liquid. Gently scrape the loose, reddish-brown copper flakes off the bar into the solution.
Rinse the Iron: watering over your container to catch all the copper. Set the cleaned iron bar aside to dry.
2. Neutralize the Leftover AcidAdd Baking Soda: Slowly add sodium bicarbonate (baking soda) or washing soda to the liquid.
Watch the Fizz: The solution will fizz violently if leftover nitric acid is present. Keep adding baking soda in small increments until the bubbling completely stops.
Check the pH: Ensure the solution is neutral (pH 6 to 8) using pH test strips.
3. Filter the Solid CopperFilter the Liquid: Pour the neutral mixture through a paper coffee filter or a laboratory filter setup.
Collect the Copper: The solid copper metal will stay in the filter. Rinse it with water, then with isopropyl alcohol, and let it dry. You now have recovered solid copper.
4. Treat and Dispose of the LiquidThe remaining filtered liquid contains dissolved iron ions and small amounts of leftover copper ions.Precipitate Heavy Metals: Add a generous amount of washing soda (sodium carbonate) or lime (calcium hydroxide) to the liquid. This will cause the dissolved metals to turn into solid sludge (metal hydroxides).
Let It Settle: Allow the sludge to settle to the bottom of the container.Dispose Safely: Filter out the sludge.
Wrap the solid sludge in a plastic bag and take it to a household hazardous waste depot. The remaining clear, neutral water can typically be poured down the drain, depending on your local municipal bylaws.
