The quantification of shifting adsorption equilibria of gold and base metals in CIP plants

Most dynamic models for the carbon-in-pulp (CIP) process incorporate single and constant isotherms without taking fouling, variation in cyanide levels and competition from base metals into account. In contrast with these simplified models, the fundamental dynamic multicomponent CIP adsorption model proposed here incorporates a shifting equilibrium isotherm. Also, an empirical model was developed for predicting the degradation of cyanide down the adsorption cascade as a function of the feed pH and feed cyanide concentration. The effect of fouling was represented by introducing an additional theoretical component which competes with gold for adsorption onto activated carbon. A shifting isotherm could have an important effect on model predictions and this was highlighted by the prediction of copper adsorption. The copper loading profile was highly dependent on changing cyanide levels and gradual displacement of copper cyanide complexes by competing species.