Biosorption of mercury by M. pyrifera and Undaria pinnatifida from the south coast of Argentina

PLAZA CAZON J.; GUIBAL E.; VIERA M.; DONATI E.

BARILOCHE, ARGENTINA

Simposio; 18th International Biohydrometallurgical Symposium; 2009

Macrocystis pyrifera and Undaria pinnatifida are brown algae which belong to Phaeophyta family. The alginate component present in cell wall of these algae is the responsible for the success in biosorption process. Methylmercury could be accumulated through the food chain and produce toxic effects on human health. The objective of this work was to evaluate the mercury adsorption capacities of M. pyrifera and U. pinnatifida. The studies consisted in: the stabilization of the biomaterial, kinetic studies, equilibrium studies in monosystem of mercury and, bimetallic system (mercury – zinc and mercury-cadmium) and the analysis and characterization of the cell wall before and after the biosorption process in monometallic system and bimetallic systems by SEM – EDAX. The stabilization of the two biomaterials was reached by treating with 0.2 M CaCl2. Four different pH values (3, 4, 5 and 6) and different contact times between mercury ion and biomass were considered in order to determinate the optimum pH and the time to reach the equilibrium. Mercury biosorption studies were carried out using different mercury concentrations (10 ppm to 180 ppm) at initial pH of 5. It was also studied the mercury adsorption in the presence of zinc or cadmium in two fixed concentration values (10 ppm and 180 ppm) and in systems with same concentration of mercury and zinc or mercury and cadmium. The results fitted very well to Langmuir model. The values of qmax obtained were 0.49 mmol/g and 0.75 mmol/g for M. pyrifera and U. pinnatifida respectively. The adsorption capacities of mercury decreased in the presence of zinc or cadmium in bimetallic systems. SEM EDAX analysis showed morphology differences and the presence of C, O, Al, Ca, Hg, Zn and Cd in the cell wall of both algae.