Cementation of copper onto brass particles in a packed bed

Abstract

The process of copper ion cementation from dilute solution was investigated using a packed bed column filled with brass particles. The influence of initial pH value of the treated solution, particle size and the solution flow rate on the cementation process was determined. It was observed that, in general, the process rate passes through an initial period of particle surface activation; a period of constant rate and a period of decreasing rate. Increasing the initial pH value of treated solution, the rate of cementation has significantly been slowed down and, at pH > 2.6, the process becomes very slow due to an H+-ions consumption and consequently measurable change of pH during the process. Using a packed bed of brass particles, it is possible to remove copper ions from feeding stream to a degree higher than 95% for about 20 - 30 minutes, i.e. an initial copper concentration of about 250 mg/dm3can be reduced to less than 10 mg/dm3. For an hour of the process time the initial level of Cu2+ can reach a value less than 1 ppm, meaning the investigated process is highly efficient. The concentration of zinc in the solution after cementation is about twice higher than the initial copper concentration in the feeding solution. The method of packed bed cementation, using brass particles, which are usually a secondary material for re-melting, could particularly be favorable instead of the conventional one, because zinc dust is being substituted with some less valuable starting material that could be upgraded on copper before its re-melting.