Sorption isotherm model for binary component sorption of copper, cadmium, and lead ions using dried green macroalga, Caulerpa lentillifera

The sorption of Cu2+, Cd2+, and Pb2+ by a dried green macroalga Caulerpa lentillifera in binary components systems was investigated. The partial competitive binary isotherm model was proven to be effective in describing the experimental data. The model and experimental data of each binary component system demonstrated that the presence of the secondary metal ion always reduced the total sorption capacity of the biomass. This implied that there existed the same pooled binding sites for the sorption of all of these heavy metal ions. Pb2+ was demonstrated to be the most uptaken species, followed by Cu2+ and Cd2+. The presence of Pb2+ more significantly decreased the sorptions of Cu2+ and Cd2+ than vice versa. Similarly the sorption of Cd2+ was more disturbed by the presence of Cu2+, than that of Cu2+ by Cd2+. The effect of pH on metal sorption could also be described using similar fundamentals with the sorption of binary metal component, and the partial competitive model could also be applied to predict the effect of pH on the sorption of these metals. It was demonstrated that a decrease in pH resulted in a reduction in the sorption capacity and sorption affinity. Finally, carboxyl, hydroxyl, sulfonate, amine, and amide functional groups in the alga could be responsible for the sorption of all heavy metals in this work.