how to make a constant pH in lead nitrate solution of varying concentration without precipitation?

[Jayalak]

Hello all,

I'm doing sorption studies of certain heavy metals (Pb, Cu, Zn, Ni, Cd, Cr) in soil (natural clay and kaolinite) with ph as a variable (2,4,7,10,12).On adjusting pH to reach a constant value using NaOH and HCl, my heavy metals in nitrate salts form are getting precipitated. thus unable to maintain the concern concentration (50ppm, 250ppm, 500ppm, 750ppm, 1000ppm).

help me out please..

thanks in advance.

 

[John Cuthber]

Because most of those metals at those concentrations will precipitate at pH10 and 12 there is no meaning to a sorption experiment in those conditions.

You might be able to stop them precipitating by adding something like EDTA, but what would be the point? In the real world, there wouldn't be EDTA present.

[studiot]

I don't usually refer to Brittanica, but clay minerals have a special chemistry due to their structure.

 

https://www.britannica.com/science/clay-mineral/Chemical-and-physical-properties