Scale formation potentials of seawater at the membrane surface of a desalination process can be eliminated by changing the chemistry of the feed water through a reversible cation exchange step before the membrane desalination process. The scale-forming cations like calcium, barium, strontium are exchanged for non-scale forming magnesium ions when contacted with a bed of cation exchanger pre-loaded with magnesium ions. The concentrate from the membrane process is used for regeneration of the ion exchanger. Elimination of scaling potential enables to achieve a higher product water recovery compared to the conventional reverse osmosis process. As osmotic pressure of a solution depends on the total molar concentration of ions, a partial replacement of monovalent sodium ions by equivalent amount of divalent magnesium ions also reduces the osmotic pressure of the feed water to the membrane. A better energy economy is possible while achieving higher degree of permeate recovery as well.

Reversible cation exchange-membrane (RCIX-MEM) process for scaling free, energy efficient desalination of seawater

240th National Meeting (2010)

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