I am looking for a good way to liquefy or extract water from superabsorbent polymer. From what I remember it was salt that can liquefy it. Since salt when dissolved will have sodium cation and therefore naturalize the polymer chain making it contract. Is that true?
This may be true, but I suggest another type of explanation. If a super absorbent polymer absorbs its maximum in distilled water it is called a fully swollen hydrogel. There are two ways of decreasing the amount of water stored without using heat.
The first one is to increase the salt load of additional water and place the hydrogel within this salted water. The salt in the water will decrease the total water absorbed by the hydrogel and the hydrogel will shrink, giving up some of its water.
A more complete and full way to make the hydrogel to give up its water is the addition of an acid. Lowering the pH of the hydrogel to below 3.5 will convert all the sodium carboxylates to the free acid form which does not absorb water. These hydrogels are pH-sensitive, and if you plot pH vs absorbed fluid, you would find a bell curve that starts around 4.5 or 5.0, tops out around 7.5 and decreases as you increase the pH until around 10.5 to 11.0.