Removing Pb2+ from Water: EPA Standards & NaCl Solution

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The discussion centers on the removal of lead (Pb) from drinking water using sodium chloride (NaCl) to precipitate lead as lead chloride (PbCl2). The Environmental Protection Agency sets a maximum safe concentration of Pb2+ at 1.00 x 10-7 M. To achieve this, the solubility product constant (Ksp) for PbCl2, which is 1.6 x 10-5, is utilized to calculate the necessary concentration of chloride ions (Cl-). It is noted that a significant amount of salt would be required, which poses environmental risks, such as harming plant and wildlife due to increased salinity in water sources. Additionally, caution is advised against using hot water, as PbCl2 is more soluble at higher temperatures, potentially leading to unsafe conditions. The discussion highlights the complexity of using this method for practical water treatment, indicating that while the chemistry is straightforward, the implications for water quality and safety are significant.
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[SOLVED] Removing Pb from water

The Environmental Protection Agency recommends that Pb2+ have a concentration not exceeding 1.00 x 10-7 M in drinking water. What concentration of NaCl could be used to remove the lead from the water to bring it to a safe level? Ksp for PbCl2 is 1.6 x 10-5. What would the drawbacks of doing this be?

Could anyone get me going with this?
 
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sveioen said:
Could anyone get me going with this?

Ksp=[Pb2+][Cl-]^2 by definition.

You are given the KSP and Pb2+ values, simply find the concentration of Cl-. You will notice that you will need a LOT of salt to do this, and creating highly saline environments in water sources kills a lot of plants and wildlife.
 
gravenewworld said:
Ksp=[Pb2+][Cl-]^2 by definition.

You are given the KSP and Pb2+ values, simply find the concentration of Cl-. You will notice that you will need a LOT of salt to do this, and creating highly saline environments in water sources kills a lot of plants and wildlife.

Wow, so it is that easy. Thank you very much gravenewworld!:smile:
 
sveioen said:
Wow, so it is that easy. Thank you very much gravenewworld!:smile:
Ok, however don't do it with hot water, or you'll kill people (PbCl2 is quite soluble in hot water).
Furthermore, precipitating Pb with Cl- obviously take in solution the anion and this one can be not appropriate itself for a drinking water: NO3- for example.
 
Last edited:
This sounds more like Chemistry 101 homework than somebody with bad well water. But, you never know.
 
jim mcnamara said:
This sounds more like Chemistry 101 homework than somebody with bad well water. But, you never know.
Agree :approve:
 

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