Science Buddies: "Ask an Expert"

I am doing a science fair project on the effect of dried fruit peels on water contaminated by heavy metals, specifically lead and copper. I didn't find any water near me that contained these, so I resorted to creating my own. I used copper sulfate to try to recreate copper and lead in my water (with my mom's supervision, latex gloves, goggles and a mask). We will also dispose of is correctly. When I used a test strip after exposing water to the sulfate, it showed that there was 30ppm copper and 50 ppm lead(I assume there's lead because the copper had lead solder). I soaked the peels in 91% rubbing alcohol and then dried them in the oven at 200 degrees. Then I broke them up in small pieces and put them in a jar. However, when I exposed the sulfated-water to the dried banana and apple peels, they had no effect whatsoever on the readings. I tried different times (20 minutes, 3 hours then overnight for soaking and still nothing happened). I also tried just raw banana peels (nothing done to them), but that didn't work either. Is it not working because of the sulfate? Multiple sources on the internet said that sulfate would function just fine for my needs, but it hasn't. Does anybody know something that might work?

Hi plazen,

Based on the description you provided it appears that you've followed a reasonable test procedure.
I'm assuming you made a dilute copper sulfate solution for testing. But I'm not certain where the lead came from.

There are some reports that fruit peels can reduce concentrations of copper or lead by 20% to 50%.
So you might expect to see your copper drop to the 15 to 25 ppm range (from the 30 ppm you posted). Keeping this in mind, you might try the following troubleshooting steps.

Are you using the test strips properly? If you made a dilute copper sulfate solution using distilled water there shouldn't be any lead present. If you used tap water the lead content should be less than 15 ppb (much lower than the 50 ppm you posted).

Are the test strips you're using capable of indicating metal concentration changes of 20% to 50%?
If not maybe you can find more sensitive test strips.

How much fruit peel did you add to the test water? You might try adding more peel to get an observable effect.

Did you stir or agitate the test water/fruit peel mixture? If not you might try stirring the water after adding the fruit peel.

I hope this helps. Please ask again if you have more questions.

A. Norman