Recovery of copper from industrial waste solution by cementation on reciprocating horizontal perforated zinc disc

Rates of Cu++ removal from waste solutions by cementation on a perforated reciprocating zinc disc were studied under different conditions of frequency and amplitude of oscillation. Disc pulsation was found to increase the rate of cementation by a factor ranging from 2.8 to 5.5 compared to cementation on stagnant disc, initial Cu++ concentration, temperature, disc diameter and hole diameter. The effect of temperature was found to fit Arrhenius equation with an activation energy of 2.95 kcal/mole which confirms the diffusion controlled nature of the reaction. Mass transfer study of the process has revealed that the data fit the dimensionless equation Sh = 89 Sc0.33.Re0.537(d/dh)-0.496. The importance of using the above equation in the design and operation of high productivity cementation reactor was pointed out.

The results obtained show that copper ions could be effectively removed from waste water effluent stream by cementation using oscillating perforated zinc discs. The present study has revealed that higher rates of mass transfer could be obtained by oscillating perforated discs. The degree of mass transfer enhancement was found to depend mainly on the vibration intensity, disc perforations diameter and disc diameter. The larger the disc diameter the lower the mass transfer coefficient, the higher the vibration intensity the higher the mass transfer coefficient. Also higher temperatures and higher initial concentrations give higher values of mass transfer coefficient. Disc pulsation was found to increase the rate of mass transfer and the rate of cementation by a factor ranging from 2.8 to 5.5 depending on the operating conditions. The dimensionless equation obtained in the present work can be used in the design and operation of batch cementation reactors as well as continuous reactors operated at low feed rate. The high residence time arising from the low feed rate and the high mass transfer coefficient caused by plate oscillation would lead to a high degree of conversion per pass. Work is underway to improve the performance of the present reactor by increasing its effective area through using a multiple oscillating plate column operated in a continuous manner.