- Antiscalants are a family of chemicals designed to inhibit the formation and precipitation of crystallized
mineral salts that form scale.
- Reverse osmosis water purifiers will reduce the pH of drinking water. Because
reverse osmosis removes the minerals in water the water will then react with carbon dioxide upon exposure
to air to form carbolic acids, thus lowering the pH
- Antiscalants have to be non-toxic, or they would not be approved by NSF for potable water applications.
- Both phosphonate and polymer based antiscalants are biodegradable over time.
- Cleaning should generally occur when the normalized flux has decreased 10% to 15%, the normalized salt content of the permeate has increased by 10%.
- There are also certain membrane-based systems that
actually counter act fouling and scaling.
- Calcium carbonate scale that has been detected early can be removed by lowering the feed water pH to
between 3.0 and 5.0 for one or two hours.
- Longer resident accumulations of calcium carbonate scale can
be removed by recycling of 2% citric acid and pH not less than 4.0 through the membrane elements.
- Silica can be removed from water by precipitation with multivalent metal hydroxides, such as Fe(OH) 3 ,
Al(OH) 3 and Mg(OH) 2 .
- This treatment removes both soluble and colloidal silica [3], [7], [8].
ou can dissolve silica with hot *concentrated* sodium or potassium hydroxide solution.This will dissolve
alumina as well, as HF does too.
