Goal
Produce potable fresh water from seawater in a low-cost, low-energy manner.
Problem
Global scarcity of clean drinking water and the high cost/energy demand of conventional desalination technologies.
Concept Summary
A highly absorbent hydrogel made from saponified starch grafted polyacrylamide selectively binds the ~90 % of seawater that is not ionically bonded to salt. The hydrogel separates fresh water from brine without external thermal or electrical energy, yielding drinkable water and a calcium-sulfate by-product.
Detailed Description
The process creates a hydrogel by graft-polymerising acrylamide onto starch (often saponified) to form a superabsorbent polymer. When mixed with seawater at room temperature and pressure, the polymer absorbs the free water while leaving dissolved salts in the brine. The gel is then separated, de-watered (producing an aqueous sulfuric-acid solution), and the fresh water is recovered. Experimental runs showed >70 % water recovery, conductivity ~306 uS/cm (~= distilled water), total dissolved solids 513 mg/L (well below WHO limits), and a gypsum (CaSO_4) by-product. No external thermal or electrical energy is required, making the method potentially scalable for small-scale, low-infrastructure deployment.
Principles
- Selective absorption
- Polymer grafting
- Hydrophilicity
- Ion exclusion
Scientific Domains
Materials
- Starch (renewable carbohydrate)
- Polyacrylamide
- Saponified polyacrylamide
- Glycerol (cross-linker)
- Aluminum ions (ionic cross-linker)
- Sulfuric acid (used in de-watering step)
Mechanisms of Action
- Hydrogel binds free water molecules while rejecting salt ions
- Physical separation of water-laden gel from brine
- De-watering of gel to release fresh water
Applications
- Drinking water supply in remote or disaster-affected areas
- Small-scale community desalination
- Emergency water purification
Claimed Performance
Fresh water yield >70 %; conductivity 306 uS/cm; TDS 513 mg/L (WHO safe drinking water); low-energy (no external heat or electricity) operation.
Experimental Evidence
Conductivity of extracted water 306.32 uS/cm; total dissolved solids 513 mg/L; sodium 25.8 mg/L; chloride 36 mg/L; water recovery >70 % in laboratory tests.
Limitations
- Scale-up and continuous operation not yet demonstrated
- Production cost of grafted hydrogel at industrial scale unknown
- Management of brine waste
