Ion Exchangers & EDI

Ion Exchange – Flexible, selective, and widely applied

Ion exchange relies on beds of synthetic resins bearing functional groups that exchange their native ions for unwanted ions in the water. Ion exchange is widely applied for softening and desalination, selective removal of contaminants (including heavy metals and PFAS), condensate cleaning, pickling‑bath and hydrochloric acid cleaning, polishing for wastewater recycling, extraction of recyclable materials, and feedwater preparation for electrolysers used to produce green hydrogen. The process is batch oriented: resins eventually become depleted of exchangeable ions and must be regenerated chemically with acid and caustic or be replaced, which requires downtime and handling of chemicals. Ion exchange strengths are its flexibility and selectivity, since different resins and functional groups can be chosen to target specific substances.

Electrodeionization (EDI) – Continuous, chemical-free deionization

EDI combines ion‑exchange resins with ion‑selective membranes and a direct electric field to deionize water continuously and without chemical regenerants. Water flows through compartments filled with mixed‑bed resins separated by selective membranes; the applied DC field forces ions through the resins and across the membranes into concentrated reject streams while simultaneously regenerating the resins in situ. EDI is commonly used as a polishing stage after reverse osmosis to produce ultra‑pure water for demanding applications such as electrolysers. Compared with conventional Ion exchange, EDI eliminates the need for acid and caustic regeneration, provides continuous operation with stable water quality (avoiding the quality swings of batch regeneration), requires less resin and smaller process vessels, and reduces both operating costs and environmental impact.

Choosing the Right Technology – When to use Ion Exchange vs. EDI

In practice, Ion exchange is often chosen when targeted removal of specific substances or larger‑scale bulk treatment is required, and intermittent chemical regeneration is acceptable. EDI is preferred when continuous, chemical‑free production of very high‑purity water is needed—especially downstream of RO—and when reduced footprint, lower chemical handling, and minimal downtime are priorities.