The mass transfer behavior of a circular rotating array of vertical cylinders was studied using an electrochemical technique which involves measuring the limiting current of the cathodic reduction of potassium ferricyanide. Variables studied were: array rotation speed, cylinder diameter, cylinder separation, and physical properties of the solution. It was found that the rate of mass transfer at the cylinder array increases with increasing rotation speed while increasing cylinder diameter decreased the rate of mass transfer, cylinder spacing within the array was found to have little effect. The data were correlated by a dimensionless equation including all affecting parameters. The reactor was tested in removing copper ions from dilute solutions and found to be promising. Possible applications of the rotating cylinder array in building electrochemical reactors and catalytic reactors e.g., photocatalytic and immobilized cell (or enzyme) biochemical reactions suitable for wastewater treatment were highlighted.