Counter-current vs co-current flow in carbon-in-pulp adsorption circuits

Carbon-in-pulp (CIP) and carbon-in-leach (CIL) technology is applied successfully to recover gold from cyanided pulps. These plants are operated on a counter-current basis allowing for small concentrations of gold to be recovered at the expense of inefficiencies such as back-mixing, additional carbon breakage by interstage pumps and difficulties in carbon inventory management. In this study, linear regression techniques were utilised in order to study the adsorptive behaviour of carbon in gold bearing solutions with the aim of determining whether a partial co-current mode of operation will be feasible in CIP operations. It has been found that these empirical techniques are able to predict the adsorption rate of gold onto activated carbon and that the point of discontinuity of the constant rate adsorption period can accurately be determined. Thus, the behaviour of a single activated carbon particle can be predicted making use of standard linear regression techniques and using inputs such as, slurry density, rate of agitation, carbon loading and carbon and gold concentration. This information can then be utilised to maximise the use of the constant rate adsorption period by using a partial co-current mode of operation and reducing inefficiencies such as back-mixing and gold loss due to the abrasive action of interstage pumping on the adsorbent.