Answer :
Geraldo can add a pollutant with slightly basic nature so he will have a solution of neutral pH of 7.
What is pH?
The pH of a solution is the negative logarithm to base ten of the hydrogen ions concentration of the solution.
The pH of 6.5 means that the solution is acidic.
By adding a pollutant which is slightly basic in nature, Geraldo will have a solution of neutral pH which is a pH of 7.
Learn more about pH at: https://brainly.com/question/24595796
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