A huge pharmaceutical company is polluting the water supply of your town.

Question

A huge pharmaceutical company is polluting the water supply of your town. You know the company uses Aqueous iron in its factory and you have a hunch that somehow this iron is finding its way into the groundwater. You have A sample of groundwater taken from a site near the property of the plant How could you go about removing iron from the sample of groundwater? Name one anion you would use and how would you use it.

Answer 1

There are several anions that will remove (precipitate) Fe^2+ from the water.  Some of these are 

• Carbonate (CO3^2-)
• OH^-
• O^2-
• PO4^3-

One could simply add, e.g. sodium phosphate (Na₃PO₄) and this would react with the Fe²⁺ to precipitate the iron as 

Fe₃(PO₃)₂