ioninvaihtokapasiteettina

Ioninvaihtokapasiteettina (Finnish for "ion exchange capacity") refers to the ability of a material, typically a solid adsorbent such as activated carbon, ion exchange resins, or clays, to exchange ions with a surrounding fluid. It quantifies how many milliequivalents of charge a gram of the material can accept or release under specified conditions, typically expressed in milliequivalents per gram (meq g⁻¹).

The capacity depends on the surface area, pore structure, and the nature of functional groups present on the adsorbent. In cation exchange resins, for example, quaternary ammonium groups provide positive charge sites that can capture negatively charged ions like chloride or sulfate. In anion exchange resins, sulfonic acid or carboxyl groups carry negative charges and bind cations such as sodium or calcium. Clays such as montmorillonite exhibit high ion exchange due to their layered silicate structure and exchangeable cations between sheets.

Measurement of ion exchange capacity is commonly performed by titration or by equilibrium adsorption experiments. A standard procedure involves saturating the resin with a known ion (e.g., sodium) and then exchanging it with another ion (e.g., hydrogen) through acid treatment. The amount of displaced ion is determined by titration, allowing calculation of capacity. Alternative analytical techniques include conductivity measurements and spectroscopic methods.

Ioninvaihtokapasiteettina is critical in many applications. Water treatment employs anion and cation exchange resins to soften water, remove heavy metals, and purify drinking water. In biochemistry, ion exchange chromatography separates proteins based on charge properties. Agricultural soil amendments use ion exchange resins to control nutrient release. The term also appears in environmental engineering for assessing soil contaminant retention and in pharmaceutical science for drug formulation.