Purolite 502E question.

[steve b]

Dear colleagues,
These kind of Purolite adsorbents are strong anion exchangers. They are not specific, but selective, which means they do not only remove the main target (NO3-), but also other anions. These are SO4--, Cl-, HCO3-, and even PO4---, among others. These adsorbents exchange the mentioned anions with Cl-. Thats why they are intended to be regenerated with NaCl: Na+ will pass the sorbent during regeneration, Cl- will be exchange by NO3- (and other anions) -> NaNO3 (in solution) is flushed out of the sorbent during regeneration (as well as Na2SO4, NaCl, etc.).
If you use NaOH for regeneration, OH- instead of Cl- will be realeased into the tank which will 1) raise the pH in your tank and 2) lead to an asymmetry between H+ and OH- and access OH- will raise the conductivity AND THE pH! Thats not what you intend, is it?

Since also HCO3- is exchanged, it is clear that you register a drop in KH.

You should keep in mind that the use of nitrate sorbents "contaminate" your tank with Cl-, which is just the lesser evil than nitrate. Dont forget about the regular water exchange in order to reduce the Cl- concentration
and to keep your water as natural as possible.


Recommended reading:
T. Nur, M.A.H. Johir, P. Loganathan, S. Vigneswaran, J. Kandasamy: Effectiveness of purolite A500PS and A520E ion exchange resins on the removal of nitrate and phosphate from synthetic water. Journal: Desalination and Water Treatment. 47 (2012) 50–58 (Sept).

Regards,
Jens (working with adsorption in biomedicine for 25 years)

That's great info, thanks and nice to have your experience on the Forum and welcome.

[Tschens]

Thanks a lot for the warm welcome! To avoid off-topic discussions in this thread, I introduced myself here:
https://forum.simplydiscus.com/showt...-and-biologist