EDI electric desalination equipment achieves continuous resin regeneration during seawater desalination through the deep integration of electrodialysis and ion exchange technologies. This mechanism has a decisive impact on the quality of the produced water. Its core principle lies in using a DC electric field to drive water molecules to dissociate, generating hydrogen ions (H⁺) and hydroxide ions (OH⁻). These ions act as natural regenerators, dynamically restoring the adsorption capacity of the ion exchange resin, thus avoiding water quality fluctuations and environmental pollution caused by traditional chemical regeneration.
In EDI equipment, the resin regeneration mechanism is achieved through electrochemical action. When seawater flows through the desalination chamber, the cations and anions are adsorbed by the resin. Simultaneously, the electric field drives water molecules to polarize at the resin interface, dissociating H⁺ and OH⁻. These ions migrate to the active sites of the cation and anion resins, respectively, neutralizing the adsorbed ions and releasing pure water molecules. For example, H⁺ exchanges with sodium ions (Na⁺) adsorbed by the cation exchange resin, restoring the resin to its hydrogen form; OH⁻ exchanges with chloride ions (Cl⁻) adsorbed by the anion exchange resin, restoring the resin to its hydroxyl form. This process requires no addition of acid or alkali chemicals, fundamentally eliminating impurities that may be introduced by chemical regeneration, providing a basic guarantee for the quality of the produced water.
The continuity of the resin regeneration mechanism is key to the stable quality of the produced water from EDI equipment. Traditional ion exchange equipment requires periodic shutdowns for chemical regeneration, during which the quality of the produced water declines due to resin saturation. EDI equipment, however, continuously drives water dissociation through an electric field, keeping the resin in a dynamic regeneration state and ensuring the continuous stability of the resistivity of the produced water. Even when the influent ion concentration fluctuates, the electric field strength can be automatically adjusted to maintain sufficient H⁺ and OH⁻ generation, thus ensuring that the resin regeneration efficiency and the quality of the produced water are not affected. This continuous operation mode is particularly suitable for scenarios with stringent water quality requirements, such as the preparation of ultrapure water in the electronics industry or the production of pharmaceutical injection water.
The regeneration mechanism significantly improves the removal of weak electrolytes from the product water. Weak electrolytes such as carbon dioxide (CO₂) and silicon (SiO₂) in seawater are difficult to remove completely using traditional ion exchange technologies due to their low degree of dissociation. However, in EDI equipment, the electric field-driven H⁺ and OH⁻ not only regenerate the resin but also react with the weak electrolytes: H⁺ combines with CO₂ to form carbonic acid (H₂CO₃), which then decomposes into water and carbon dioxide gas; OH⁻ reacts with silicic acid (H₂SiO₃) to form silicates, which are adsorbed by the resin and discharged through the concentrate. This process significantly reduces the content of weak electrolytes in the product water, achieving a resistivity of over 18 MΩ·cm, meeting high-purity water standards.
The resin regeneration mechanism also ensures product water quality by inhibiting ion back-diffusion. In traditional electrodialysis, the ion concentration difference between the concentrate and desalination chambers can cause separated ions to redisperse into the desalination chamber, reducing product water purity. In EDI equipment, the H⁺ and OH⁻ generated during regeneration preferentially fill the resin pores, forming an ion barrier that effectively prevents ions from reverse osmosis into the concentrate chamber. Simultaneously, the electric field-driven directional migration further enhances ion separation, reducing ion leakage in the product water to extremely low levels.
The contribution of the regeneration mechanism to the long-term operational stability of the equipment is also significant. Chemically regenerated resin is prone to performance degradation due to acid and alkali residues, while EDI's electrochemical regeneration completely avoids this problem, extending resin lifespan. Furthermore, the H⁺ and OH⁻ generated during regeneration neutralize adsorbed organic matter on the resin, reducing the risk of resin contamination and maintaining long-term efficient operation. This stability directly translates into consistently reliable product water quality, reducing the risk of water quality fluctuations due to equipment failure.
The resin regeneration mechanism in EDI electric desalination equipment comprehensively ensures product water quality through multiple pathways, including electrochemical action, continuous operation mode, deep removal of weak electrolytes, suppression of ion back-diffusion, and improved equipment stability. Its core advantage lies in the seamless integration of resin regeneration and ion separation processes, realizing a technological leap from "intermittent treatment" to "continuous purification" in seawater desalination, and providing a revolutionary solution for the field of high-purity water preparation.
