The negatively charged functional groups on the resin beads attract and bind to positively charged ions (cations) in solution. These cations are then exchanged for other, generally less problematic cations already bound to the resin, such as sodium (Na+) or chloride (H+) ions. This process effectively removes unwanted cations from solution.
Cation exchange resins are commonly used in water softeners to remove hardness-causing calcium and magnesium ions and replace them with sodium ions.
Cation exchange resins can also be used to remove all cations in water by exchanging them for hydrogen ions (H+), which then combine with anions to form water.
