Chitosan Gel Beads as a New Biosorbent for Molybdate Removal

Abstract

Metal ion sorption on chitosan is controlled by intraparticle mass transfer. This paper examines the suggestions of producing gel beads to enhance these diffusion properties. This technique consisted of two stages: firstly dissolving chitosan in acetic acid solution followed by dropping the resulting viscous solution through a thin nozzle into a casting alkaline solution (NaOH). This sorbent was tested for molybdate removal. The optimum pH range corresponded to an acid medium. A cross-linking stage in glutaraldehyde solution increases resistance to acid preventing gel beads dissolving. Metal ion concentration, particle size, chitosan conditioning and competitor ions were studied in terms of equilibrium and kinetic performances. The intraparticuiar diffusion coefficients were evaluated and sorption capacities as high as 750 mg (dry)g−1 were obtained. Dynamic removal of molybdate in a fixed-bed reactor was also studied in terms of flow rate and column size effects.