Synthesis and characterization of an amphoteric resin for use in membrane-free electrodeionization

Abstract

• A novel amphoteric resin was prepared and characterized. • It has better purification property than weak acid resin. • It is much easier to be electrically regenerated than strong acid resin. • It can replace conventional resins in MFEDI to produce high-purity water. Previously, we invented and investigated membrane-free electrodeionization (MFEDI), a novel deionization technique that uses ion exchange resins as the critical material, for the production of high-purity water. However, the functional materials used in MFEDI are common resins that cannot simultaneously achieve effective adsorption, easy electrical regeneration, and good conductivity. For instance, strong acid resin, a cation exchange resin commonly used in MFEDI, cannot be easily electrically regenerated; weak acid resin can be easily regenerated, but has poor conductivity and adsorption properties. There are currently no available resins that can meet all of the requirements of conductivity, adsorption and regeneration properties. In this study, a novel amphoteric resin was prepared and characterised. This amphoteric resin contained much more cationic functional groups than anionic functional groups, behaving as a medium-strength acid resin due to the introduction of anionic functional groups. The prepared amphoteric resin exhibited better purification property than weak acid resin, and could be electrically regenerated more easily than strong acid resin. When the amphoteric resin was coupled with strong base resin and the conductivity of the purified water was kept below 0.10 µs/cm, the water recovery and energy consumption were 74.60% and 0.84 kWh/m 3 water, respectively. By contrast, the energy consumption and water recovery were 40.74% and 2.65 kWh/m 3 water for strong acid resin, and 64.44% and 1.53 kWh/m 3 water for weak acid resin under similar conditions. Clearly, the developed amphoteric resin significantly improves the MFEDI properties.