How do superabsorbent polymers work?
Water molecules are drawn into the network across a diffusion gradient - formed by the neutralization of the polymer backbone usually with Sodium (NaOH) or Potassium (KOH). The polymer chains want to straighten but cannot due to the cross-linking. Thus, the particles expand as water moves into the network.
The water is held tightly in the network by Hydrogen-bonding.
Superabsorbent Polymer Network
Key Uses for SAPs:
Another benefit of these polymers – when dealing with waste containing metals – is the polycarboxylate (-COOH, -COONa) nature of the polymers. This –COOH group has a very high ion exchange capacity for soluble metal cations. Many wastes containing heavy metals such as Lead, Mercury and Chromium will pass the EPA Toxic Characteristic Leachate Procedure (TCLP) after solidification with Superabsorbent Polymers.
Superabsorbent Polymer is being used at many environmental sites to solidify waste so that it passes Paint Filter Test (EPA 9095). The polymer will absorb many times it weight in water with less than 1% increase in waste volume. By avoiding an increase in the waste volume, significant savings can results with fewer loads to ship and fewer yards of landfill disposal fees.
The advantages of Super absorbent Polymers over mineral or plant-based absorbents include:
- Faster cure time
- Elimination of dust problems
- Little or no increase in waste volume
- Less yards or tons = Lower landfill fees
- Fewer loads to ship = Lower transport costs
- Exchanges and retains soluble (Heavy) metals to pass TCLP
- Non-reactive. Will not generate exothermic reaction like lime.
For more information on the history and basic chemistry of Super Absorbent Polymers visit: