Study On The Parameters Influence And Regeneration Mechanisms Of MFEDI

Membrane-free electrodeionization(MFEDI) is a novel and environment-friendly desalination technique, which originates from EDI and realized the membrane-free regeneration of resins innovatively.MFEDI accomplished an environment-friendly deionization process by alternating with service and electro-regeneration.During service,MFEDI removed ions in aqueous phase by ion exchange resins in column.During electro-regeneration,the shift of ion exchange equilibrium toward regeneration was promoted by high electric field and salt ions desorbed from resins were transferred out of column by high purity water simultaneously.This thesis studied process parameters of MFEDI and investigated the regeneration mechanism of MFEDI.Major research works included three parts:the influence of resin layer parameters,the influence of regeneration parameters,the investigation of regeneration mechanism.Experimental results showed that the mixed weak-acid and strong-base resins(D113-550A) in the lower layer determined the performance of MFEDI.The optimal volume ratio and layer height of D113-550A were determined as 1:2 and 30cm respectively by investigating their influence on the performance of MFEDI.In the same way the optimal regeneration parameters were obtained,which were:duration 20min,flow velocity 25m/h,current density 100A/m2.The energy consumption and water recovery of MFEDI under optimal process parameters were 0.594 kWh/m3 water and 82.4%,respectively.The experimental results of electro-regeneration of different mixed resins showed that there seldom existed the backward electro-migration of cation in D113. The anions mainly migrated in 550A and the electrical conductivity of mixed resins were decided by the counter ions of 550A.Water dissociation mainly existed between D113 and 550A and contributed over 82.4% of the total H+ and OH- ions for regeneration.