Desalination of water - by electrodialysis with cation exchange resin pre-treatment

摘要

The parent patent describes a process for the desalination of water by electrodialysis with pretreatment of the water with ion exchange resins so that the hardness and/or the alkalinity of the water is wholly or partially removed. In this addn. the process is improved by pretreating the water with a cation exchange resin to replace the hard cations by H+ ions and/or Na+ ions depending on the properties of the water, especially using H+ ions to neutralise HCO3 ions, and regenerating the exhausted ion exchange resin. The pretreatment of the water, resulting in the removal of HCO3 ions with associated Ca++ and Mg++ ions reduces the loading on the electrodialysis unit, giving higher throughputs and reduced power consumption per unit vol. treated.