In this work, the single and multi-metal ion exchange, Na+/H+/Cd2+, Na+/H+/Pb2+, Na+/H+/Cu2+, Na+/H+/Zn2+ and Na+/H+/Cd2+/Pb2+/Cu2+/Zn2+, has been studied in a continuous mode using a fixed-bed column packed with Na-loaded macroalgae Pelvetia canaliculata as the cation exchanger. The breakthrough curves for all the systems studied were obtained using initial metal concentrations of 20 mg/L. A mass transfer model, including the mass balances to the packed bed column and to the thin plates of algae particles, assuming a LDF model, and complementary equations (as mass action law equilibrium relations, initial and boundary equations), was able to fit well the experimental data. An overshoot in the outlet of Cd and Zn concentrations was observed and explained by competitive uptake with Pb and Cu ions. Desorption using 0.1M HNO3 as eluent was fast and effective. Finally, an ion-exchange pilot plant was tested for the treatment of a multi-metal synthetic solution using the natural macroalgae.