Chemical Used to Remove Hardness of Water

Chemicals for removing water hardness mainly include sodium carbonate, phosphates, ion exchange resins, reverse osmosis, and chelating agents.

Sodium carbonate (Na2CO3, commonly known as soda): Sodium carbonate can be used to soften temporary hard water (carbonate hardness). It reacts with calcium and magnesium ions in water to form calcium carbonate (CaCO3) and magnesium carbonate (MgCO3), which are precipitates that are insoluble in water and can therefore be removed by filtration. This method is suitable for removing some temporary hardness and permanent hardness in water. 

Phosphates: Phosphates, such as sodium tripolyphosphate (Na5P3O10), can form insoluble complexes with calcium and magnesium ions in water, thereby reducing hardness. This method is often used in industrial water treatment. 

Ion exchange resins: Ion exchange resins can effectively replace calcium and magnesium ions in water. The resin contains sodium or potassium ions, and when hard water passes through the resin, the calcium and magnesium ions are replaced by the sodium or potassium ions on the resin. This method can continuously adjust the hardness of water. 

Ion exchange resins are usually composed of polymers with charge sites, which can reversibly exchange ions with cations and anions in water to achieve the purpose of removing ionic pollutants. In practical applications, commonly used cation exchange resins include strong acid cation resins and weak acid cation resins. For example, Comcess™ 001*7 resin is a high-performance Weak Acid Cation Exchange Resin suitable for industrial water desalination, softening and dealkalization applications. It can also remove all hardness in high-salinity water and can be used in combination with strong acid cation exchange resins to improve desalination efficiency and cycle water production.

Reverse Osmosis: Although reverse osmosis is not a chemical, it is a physical method that removes most ions from water, including calcium and magnesium, through a semipermeable membrane. This method can be very effective in reducing water hardness. 

Chelating agents: Chelating agents such as EDTA can form stable complexes with metal ions (including calcium and magnesium), thereby helping to reduce water hardness. This method is suitable for situations where precise control of water quality is required. 

When using these chemical agents, the appropriate method and dosage should be selected according to the specific water quality situation and the required water quality standards.