Mass transfer characteristics of reciprocating screen stack electrochemical reactor in relation to heavy metal removal from dilute solutions

Rates of mass transfer were measured for copper deposition from dilute acidified copper sulphate solution on reciprocating arrays of separated and closely packed screens by the limiting current technique under different conditions of amplitude, frequency of oscillation and copper ion concentration. The mass transfer data for the diffusion controlled copper deposition at the limiting current from a solution of constant concentration were correlated by the equations:jD=0.732Rev−0.35for the closely packed screen array, andjD=0.98Rev−0.38for the separated screen array.A mathematical model based on the surface renewal theory was found to agree fairly with the above equations. Study of the removal of copper by constant current electrolysis at the limiting current using an insoluble lead anode has shown that the reactor is capable of reducing copper ion concentration below the maximum permissible value in a time which depends on the operating conditions.The potential of using the present reactor for processing sparingly soluble reactants such as immiscible organic liquids, organic solids and gases which need to be dispersed prior to reacting at the electrode was highlighted. Also the possibility of using oscillating screen array as a catalytic reactor suitable for conducting liquid–solid diffusion controlled catalytic reactions such as removal of organic pollutants from industrial effluents by wet oxidation was noted.