Influence of Hydrolysis Mechanisms on Molybdate Sorption Isotherms Using Chitosan

Abstract

Molybdate sorption using chitosan sorbents has proved to be strictly controlled by the pH of the solution. Sorption isotherms exhibit a sigmoid trend, which has been correlated to the appearance of polynuclear hydrolyzed species, the most favorable species for sorption on chitosan. Sorption capacity exceeds 7 mmol·g−1, which corresponds to a molar ratio between Mo and the amine group significantly higher than 1. The formation of complexes in a pendant fashion and/or the ion-exchange mechanism of polynuclear metal ions are suspected to occur between polynuclear molybdate species and protonated amine groups, though several amine groups can interact with the same polynuclear molybdate group.