Key Factors Affecting Electrical Regeneration Efficacy Of Membrane-free Electrodeionization

Membrane-free electrodeionization(MFEDI)is a novel deep desalination technology.Because of the advantages of membrane free electrodegeneration,it has a better application prospect than EDI in the field of high purity water preparation.In previous studies,MFEDI has achieved long-term stable operation at a low flow rate,but there will also be some cases of poor resin regeneration effect,such as cationic difficult regeneration.For better industrial application,this paper takes second-level RO outlet simulated water as MFEDI inlet water and systematically studies the influence of three key factors,namely resin layer structure,regeneration parameters and polarity reversal,on electrical regeneration efficacy under the condition of high flow rate.The experimental results show that the structure of resin layer can significantly affect the efficacy of electrical regeneration.In the operation of more than 50 cycles,the addition of anion resin isolation layer can effectively inhibit cationic reverse migration,improve the resin regeneration efficacy,and the more isolation layer,the better the efficacy.The weak-acid and strong-base resin layer at the bottom plays a crucial role in the absorption and regeneration of high valence cations in the water.Without the weak-acid and strong-base resin layer,the phenomenon of continuous accumulation of high valence cations,continuous increase of regeneration voltage and deterioration of water quality will occurs in the system.In addition,the lower proportion of weak-acid resin in the weak-acid strong-base layer,the worse regeneration efficacy.When the weak acid resin:strong base resin is 1:2,the regeneration efficacy is the best.The experimental results show that the regeneration parameters can also significantly affect the efficay of electrical regeneration.In the study of regeneration parameters,it is found that the regeneration time,regeneration voltage and regeneration velocity are all conducive to resin regeneration,but there is a marginal effect.To sum up,the regeneration time of 20min,regeneration current density of 175A/m2,and regeneration flow velocity of 55m/h are appropriate.The experimental results also show that polarity reversal has a significant effect on the efficacy of electrical regeneration.In the study of electrical regeneration with polarity reversal,it is found that polarity reversal can effectively solve the problem of unbalanced regeneration of cations and anions and improve the regeneration efficacy.When the frequency of polarity reversal is 2:1,the balance of cations and anions regeneration is the best.In the continuous 50-cycle operation,the electrical regeneration with polarity reversal makes the effluent quality of MFEDI stable at 0.056?0.060 ?S/cm,and the regeneration voltage stays at 393?411V,indicating that the system has good regeneration efficacy.