Difference Between Ion Exchange Resin & Antiscalant

When insoluble salts in the membrane element are constantly concentrated and exceed their solubility limit, they will occur in the RO membrane surface scaling phenomenon, and the higher the recovery rate, the greater the risk of scaling. Formulating a reasonable program in advance to prevent insoluble salts from exceeding their solubility and triggering precipitation and scaling is particularly important. Common methods used in the water treatment field are anion and cation exchange resins and chemical antiscalants. Both of them stop the water from producing scale to clog the RO membrane.

Ion Exchange Resin

Na-type cation exchange resin with a large number of sodium ions has a stronger affinity with Ca²⁺, Mg²⁺, and can release Na⁺ to combine with Ca²⁺, and Mg²⁺. Na⁺ in the resin is continuously replaced by Ca²⁺ and Mg²⁺ until saturation, so that the content of calcium ions and magnesium ions in the water is reduced, and the hardness of the water decreases. The replacement and regeneration process of anion and cation exchange resin specifically can learn from softening & regeneration of ion exchange resin.

Ion exchange resin

A softening unit consisting of a water tank and a salt tank

Ion exchange resin softening equipment

Chemical Antiscalant

Antiscalant can form stable soluble chelates with calcium ions and magnesium ions in water, increasing the solubility of calcium and magnesium salts, inhibiting scale generation; antiscalant dissolved in water will also produce ions with negative electrode, adsorbed on the surface of the microcrystalline formation of a double layer of negatively charged, double layer of static repulsive force between the particles can be prevented from further collision with each other to grow up, hindering the generation of scale. As for the specific process, you can learn from antiscalant introduction.

Antiscalant

Dosing equipment consists of 3 dosing tanks and metering dosing pumps

Antiscalant dosing equipment

Differences between ion exchange resins & antiscalants:

Ion Exchange Resin	Antiscalant
Complete removal of ions	Prevent ions from crystallizing and precipitating, ions do not disappear.
No new impurities introduced	Residual chemicals
Applied in more scenarios	Antiscalants are not recommended for pure water systems because it is not easy to prove whether the chemical can completely remove ions.
Better results, but higher cost	Since there is no ion removal, the effect is not as good as resin softening, but it is better for a lower price.
Renewable with salt	Non-renewable, add new chemicals