John has given you some really good advice for starting this project. Please do be careful.
This is a really great project idea! The problem with older printed circuit boards is that they contain a combination of copper, lead, and tin. The copper is valuable and could be recycled if it could be separated from the toxic lead. However, this is going to be a very challenging science project.
The basic procedure for recovering the copper will be to dissolve the copper, lead, and tin in either an acidic or basic solution, and selectively recover the copper by precipitating the lead and using electroplating to recover the pure copper. You need to read scientific references to find out what has been done on this topic in the past.
Here are some references on this topic reporting different approaches to solving this problem. Unfortunately, I could not find any articles with complete access to all of the details, but there is useful information in the abstract and the figures for each article. There is a wide variety of approaches for copper recovery, so this suggests that no one has developed the perfect protocol yet, so this is definitely a worthwhile topic to investigate.
Here is a reference that used a dilute caustic solution to dissolve the metals. The lead was precipitated, and the copper was recovered by electroplating.http://www.sciencedirect.com/science/ar ... 499190037O
This paper describes a method for recovering lead and copper from nitric acid etching solutions used to manufacture PCB’s. The nitric acid was removed and the pure copper was recovered by electroplating; the Sn was precipitated by adjusting the pH. The figures and tables from the article are included with the abstract on this article. http://www.sciencedirect.com/science/ar ... 6X03000458
Here is an interested article that reports a method for leaching copper from printed circuit boards using microbial leaching. Unfortunately, only the abstract is available. http://www.tandfonline.com/doi/abs/10.1 ... -200034763
Here is an abstract that reports solubilizing the lead, tin, and copper in nitric acid, and precipitation of the tin. The lead and copper are selectively deposited at the cathode and anode electrodes, respectively. This procedure sounds like it is worth trying.http://onlinelibrary.wiley.com/doi/10.1 ... ated=false
Here is an abstract that includes some details. The copper was selectively dissolved from the pcbs with an ammonium-ammonium sulfate/chloride solution, extracted in a solvent called alkyl substituted 8-hydroxy-quinoline, and then recovered by electro deposition.http://www.sciencedirect.com/science/ar ... 6X07001168
Here’s an abstract that used electroplating to recover the copper. Figures are included.http://www.sciencedirect.com/science/ar ... 9406004614
Here is basic information on electroplating, which you will need to use to recover the copper:http://chem1.eng.wayne.edu/~yhuang/Pape ... g_ECHP.pdf
You will need more details about the exact protocols used so it would be very worthwhile to visit a local university library to look up some of these references or similar references. The details should be included in the materials and methods sections. Or, you could send an e-mail message to the primary authors of the more recent papers and perhaps they would send you the information that you need.
You can do a search for “Google Scholar,” and then search for information about recovering copper from printed circuit boards (pcb's) . Using Google Scholar will bring up the scientific references that you need for background information for a science project.
You could also visit a local recycling company and ask for additional information.
Here is a demonstration for dissolving copper in nitric acid. This would also dissolve the Pb and Sn. Please note that nitric acid is hazardous and you will need a laboratory and protective equipment to work with this acid. http://www.angelo.edu/faculty/kboudrea/ ... u_HNO3.htm
And, here are the chemical equations for the reaction:http://pubs.acs.org/doi/pdf/10.1021/ed067p183.2
The entire process for recovering copper from pcb’s is very complex. For a science project, I would recommend limiting your experiments to one aspect of the process. For example, you could optimize the dissolution of the metals from the pcb’s, or you could work with known mixtures of lead, copper, and tin, and optimize the electroplating process.
And. John has made a very good point about the hazardous nature of this project. You will definitely need to get prior approval for doing this project since it involves using hazardous chemicals. Here is the information on this topic from this website: http://www.sciencebuddies.org/science-f ... chem.shtml
Please post again in this topic when you have more questions. Good luck!