Hello, thank you for taking the time to post your question!
The relationship here would be an inverse relationship … meaning that the more dissolved solids there are in the water, the less water sodium polyacrylate will absorb. You see this inverse relationship show up in a lot of different applications where absorbent polymers are used …. Places like diapers, agriculture, and wastewater treatment.
Hopefully that gets you moving in the right direction! Feel free to reach out if you have any questions beyond that on how the process works :)
