Calcium Inhibition of Polyacrylamide Gel Hydration Is Partially Reversible by Potassium

Abstract

Hydration of a commercial hydrophilic polyacrylamide gel in 20 meq Ca(NO 3 ) 2 /liter was reduced to <10% of the maximum hydration in deionized water. Repeated soaking with deionized water to remove soluble salts restored hydration to ≈ 30% of maximum. Incorporating KNO 3 at concentrations ranging from 5 to 40 meq·liter -1 with the Ca(NO 3 ) 2 in the hydration solution partially reversed the Ca 2+ inhibition of hydration following repeated soaking. Potential hydrogel hydration increased to 50% of maximum with 40 meq K + /liter. Potassium nitrate supplied separately following hydration in Ca(NO 3 ) 2 was much more effective at reversing Ca 2+ inhibition of hydrogel hydration than joint application. Potential hydrogel hydration (following repeated soaking) was doubled after treatment with 5 meq KNO 3 /liter and reached 77% of maximum at 40 meq KNO 3 /liter.