Demineralization is a type of water purification. While it can refer to any treatment process that removes minerals from water, the term demineralization is typically reserved specifically for ion exchange (IX) processes used for near total removal of ionic mineral contaminants. Often, the terms demineralization and deionization are used interchangeably.

IX demineralization utilizes both cation and anion exchange resins, sometimes even in the same column or bed. Following demineralization, the treated water will be of a high level of purity comparable to distilled water, but typically at a much lower cost.