CALCIUM INHIBITION OF POLYACRYLAMIDE-GEL HYDRATION IS PARTIALLY REVERSIBLE BY POTASSIUM

Hydration of a commercial hydrophilic polyacrylamide gel in 20 meq Ca(NO3)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 almost-equal-to 30% of maximum. Incorporating KNO3 at concentrations ranging from 5 to 40 meq.liter-1 with the Ca(NO3)2 in the hydration solution partially reversed the Ca2+ 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(NO3)2 was much more effective at reversing Ca2+ inhibition of hydrogel hydration than joint application. Potential hydrogel hydration (following repeated soaking) was doubled after treatment with 5 meq KNO3/liter and reached 77% of maximum at 40 meq KNO3/liter.