The mechanism of cobalt biosorption

Abstract

Nonliving biomass of the common seaweed Ascophyllum nodosum is capable of accumulating cobalt from aqueous solutions to the extent of 160 mg Co²⁺/g. Successful desorption of cobalt from the biomass by acidic CaCl₂ solutions revealed that the metal uptake phenomenon is reversible, implying physical sorption of cobalt. Chemical and instrumental analysis including electron microscopy, infrared (IR) spectroscopy, X-ray dispersion and diffraction analysis provided supporting evidence that the biosorption mechanism involves predominantly ion exchange. Alginates of the cell wall (-COOH groups) play an important role in cobalt binding. Coordination and sorption in the cell wall structure occur simultaneously and rapidly whereas penetration of cobalt into the cell occurs at a lower rate.