What chemical is frequently used to remove hard minerals from water?

The use of sodium or potassium in water treatment is often associated with the process of softening hard water. Hard water contains high concentrations of calcium and magnesium ions, which can lead to scale build-up in pipes and appliances. Sodium or potassium ions are used in ion exchange processes, where they effectively replace these hardness-causing ions. This exchange helps to reduce the overall hardness of the water, making it more suitable for various applications, such as drinking, cooking, and industrial processes.

While chlorine is typically used for disinfection to eliminate pathogens, fluoride is used primarily for dental health, and calcium carbonate is itself a mineral that contributes to water hardness rather than removing it. Thus, sodium or potassium is the appropriate choice as they specifically address the issue of hard minerals in water.