Ion exchange is a reversible chemical process where an ion in solution is exchanged for a similarly charged ion on a solid particle, commonly used for water purification and hazardous waste treatment. This method can effectively remove low concentrations of toxic metals and is applicable in various industries such as pharmaceuticals, food and beverage, and nuclear reprocessing. While ion exchange has advantages in treating inorganic and organic waste, it also has limitations, including chemical waste production and fouling issues with resins.