Adsorption of metal cations from aqueous solution onto a natural and a model biocomposite

Batch adsorption studies have shown that a solid material (CACMM) extracted from a cactus was able to sorb Cu2+, Cd2+, Cr3+, CrO42−, Fe3+, Ni2+, Pb2+ and Zn2+ from aqueous solutions in the concentration range 100–1000 mg l−1. Fractions of CACMM with different particle diameter presented different sorption patterns upon the studied metal cations. Copper retention was much greater than that of other cations for all the fractions under identical experimental conditions with a maximum efficiency of 84% for 1000 mg l−1 Cu2+ solutions. Adsorption magnitude onto large particles of CACMM1 (450 (μm) decreased in the series Cu2+>Ni2+>Cr3+>Pb2+>Zn2+>Cd2+>Fe3+ that correlates with the stability constants of the respective oxalate complexes indicating that the interaction of the metal cations follows a surface adsorption–complexation mechanism. The composition of a model composite, which simulates the sorption capacity of the natural cactus powders upon copper, was found.