Nano-titania-crosslinked chitosan composite as a superior sorbent for antimony (III) and (V)

• First report on antimony sorption by nano-TiO2 impregnated chitosan beads.
• The synthesised beads are better sorbents for both Sb5+ and Sb3+ than neat nano-TiO2.
• Stable under wide solution pH values and typical column operation conditions.
• Stable to irradiation and sorbs antimony from strong complexing medium.
• Sorbs ppb level Sb ions from typical nuclear reactor decontamination formulation.

Removal of radioactive antimony, especially at low levels, is a difficult problem faced by nuclear power plants all over the world. Further, antimony is classified as a pollutant of priority importance by the United States and the European environmental protection agencies. Chitosan, a biopolymer well known for its sorption properties, can also serve as a stable matrix for inorganic sorbents such as titania on crosslinking. A robust high performing sorbent for antimony, in the form of stable beads, has been prepared using nano-TiO2 and chitosan. Raman spectra of the beads confirmed the incorporation of nano-TiO2 in the chitosan matrix. The sorbent exhibited complete sorption of antimony from aqueous solutions with antimony concentrations ranging from as low as 150 ppb to as high as 120 ppm. The sorption dependence on equilibrium pH has been investigated. The beads have been shown to be effective sorbent of antimony in both +3 and +5 oxidation states. The sorption properties of the beads were attributed to the TiO2 component present in the beads, while the crosslinked chitosan provided strong matrix and influenced the formation of much needed stable spherical beads suitable for real life large scale applications. The beads exhibited high sorption efficiency in the column mode, and were found to be physically stable at a flow rate of one bed volume per minute.