Ion-Exchange-Assisted Electrochemical Removal of Heavy Metals from Dilute Solutions in a Stirred-Tank Electrochemical Reactor: A Mass-Transfer Study

The rate of diffusion-controlled removal of Cu2+ from a dilute solution containing a fluidized bed of ion-exchange resin in a batch stirred parallel-plate electrochemical reactor was investigated. The variables studied were the concentration of ion-exchange resin, impeller rotation speed, and impeller geometry. The rate of mass transfer of Cu2+ removal was measured in three cases, namely, (i) ion exchange without electrolysis, (ii) electrolysis without ion exchange, and (iii) combined electrolysis and ion exchange. The presence of ion-exchange resin during electrolysis was found to increase the rate of Cu2+ removal by a factor ranging from 1.18 to 1.78 compared to that obtained by electrolysis alone. A simple mathematical model was developed to account for the enhancing effect of ion-exchange particles. The electrical energy consumption decreased in the presence of ion-exchange resin by an amount ranging from 3.6% to 53%. The radial-flow impeller was found to give higher rates of removal than the axial-flow impeller.