Cobalt removal is an important step in zinc hydrometallurgy, in which by adding zinc dust and catalyzer, cobalt ion is gradually removed. Reasonable operation of cobalt removal process requires online detection of cobalt ion concentration, which indicates the current state of cobalt removal. The aim of this paper is to build a model capable of predicting cobalt ion concentration online. A kinetic model was built based on a mechanism study. ORP (oxidation-reduction potential), which can be detected online, was introduced into the kinetic model by applying the kinetics of electrode reaction. The kinetic model shows satisfying tracking ability but limited accuracy. To overcome the limitation in accuracy, a data-driven compensation method was proposed and integrated with the kinetic model. Test results show that the proposed integrated model can provide an accurate prediction of outlet cobalt ion concentration in time.