Modeling and simulation of the paired recovery of metal ions from emulated e-waste solutions in an RCE electrochemical reactor in a continuous mode of operation

This work presents the mathematical modeling, simulation, and experimental validation of a paired metal ions recovery process in a rotating cylinder electrode (RCE) electrochemical reactor in a continuous mode of operation. The process involves the recovery of copper, Cu(II), and silver, Ag(I), ions cathodically with the simultaneous recovery of lead, Pb(II), ions anodically. The experimental process was implemented in a traditional RCE electrochemical reactor, with a stainless-steel cylinder working as a cathode and six-dimensional stable plate anodes (DSA) concentric to the cathode. The experimental scheme consisted of a central composite design (CCD) with three response variables, the Cu(II), Ag(I), and Pb(II) conversion as a function of the rotating speed (rpm), current density (A m(-2)), and flow rate (cm(3) min(-1)). Second-order empirical polynomials were fitted to the Cu(II) and Ag(I) conversion experimental data, while for Pb(II) conversion, a first-order polynomial was fitted. The hydrodynamics and tertiary current distribution phenomena were modeled and simulated numerically using the commercial computational fluid dynamics (CFD) software COMSOL Multiphysics. The CFD models obtained were validated with the experimental information from the experimental design. Low deviation values of the theoretical approximation to the experimental values were obtained. Also, empirical models were developed from the experimental design, which are useful for predicting the response variables in the space design, while the validated CFD models can predict the RCE electrochemical reactor behavior at any operation condition.