Research Of Phosphonic Acid Ion Exchange Resin For Preparation Of High Purity Water For RO/MFEDI

Membrane-free electrodeionization(MFEDI) is a technology to achieve high purity water by ion exchange resin adsorption and regeneration of electric power. It has the advantage of acid and no acid-base which lead to environmental pollution, and no ion exchange membrane which lead to membrane pollution. MFEDI include two parts:treatment and regeneration. In the treatment progress, ion exchange resin adsorb impurity ion in solution; in the regeneration progress, under the action of direct current, ions remove from resin phase to liquid phase, and are washed away by water. It can be seen that ion exchange resin plays a decisive role in the whole MFEDI progress.At present, MFEDI is often filled with weak acid resin-strong base resin in the inlet to adsorb ions, and filled with strong acid resin-strong base resin in the outlet to ensure water quality. The former has strong electric regeneration and weak adsorption capability, so the water quality is poor and does not meet the quality of high purity water. The latter has strong adsorption and weak electric regeneration, so it is suitable to remove small amount of impurity ions, and to ensure the water qualityIn this paper, the performance of phosphonic acid resin was studied systematically due to the shortage of weak acid resin-strong base resin and strong acid resin-strong base resin. The phosphonic acid resin was used for the running of RO/MFEDI to explore the possibility of phosohonic acid resin applied to MFEDI. The study include three parts: the study of resin properties, comparison of effect in process for selecting resin, and the optimization of operating parameters.It was shown that the trend of electrical conductivity of macroporous phosphonic acid resin and gel-type phosphonic acid resin are same as that of weak acid resin. The order is R-H< R-Ca< R-Na. the treatment and regeneration effect of gel-type phosphonic acid resin(GPAR) is better than macroporous phosphonic acid resin(MPAR) and weak acid resin. The optimal operating parameters were:treatment flow rate of 30m/h, treatment time of 160min, regeneration current density of 75A/m2, regeneration flow rate of 30m/h, regeneration time of 20min. The result reveals that gel-type phosphonic acid resin(GPAR) could successfully apply to MFEDI to achieve high purity water, and provides a strong support for subsequent research.