Expert: Dr. Henry Boyter, Jr. - 5/16/2007

Question
QUESTION: hello,
i am trying to make a water filter for my school project. I have searched google to find how can i make one to filter ions in water but it usually gives me chemicals that i cannot buy.
do you have any suggestions on what kitchen chemicals or easily reachable things like baking soda can i use to filter water ions like lead, chlorine, aldrin, fluorine etc.

ANSWER: To properly answer, I need to know what will be your source of the water.  Tap, well, river, etc.

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QUESTION: the teacher did not tell us but she said that she will proide us with a sample of water. i think it to be more likely to be tap. but in case if it has lead, aldrin ,benzene, cadmium but specially need to remove chlorine, calcium or magnesium
thank you

Answer
If tap water, nothing in the kitchen will work.  The levels will be so low that special chemcials and equipment will be needed.  The things you list will be removed by activated carbon (for organics), ion exchange resins (for metals), or reverse osmosis Larger metals and organics) or a combination of the three.  You can get activated carbon where they sell aquarium supplies and just use that and a good coffee filter for a crude version.  There is no way in a school lab to measure the levels of these materials present.  You need a commercial or advanced lab, so showing it works will not be possible.

If the water is more heavily contaminated with ions such as iron, chromium, and other heavy metals, you could add lye (sodium hydroxide)from the kitchen.  This would cause the precipitation of the metal hydroxides and again you could use a coffee filter.  With tap water, their concentration will be too low to make this work.

If there are solids present, like in river water, you can just use the coffee filter.  The other option with tap water is to distill it away from the materials you mention, except that benzene will not be removed.  

I think your procedure for a kitchen version is to add lye to pH 8 and filter, then filter that water through activated carbon.  If the water is already pH 8, skip that.  Anything else takes special chemicals.