Synthesis, characterization and sorption behavior of zirconium(IV) antimonotungstate: An inorganic ion exchanger

Present investigation deals with the hydrothermal synthesis and characterization of a new heteropolyacid salt; zirconium(IV) antimonotungstate. Three different analogues of inorganic cation exchanger zirconium(IV) antimonotungstate have been prepared by mixing potassium pyroantimonate and sodium tungstate into aqueous solution of zirconium oxychloride in the ratio of 2:1:1. The molar concentration of these three metal ions and synthesis conditions such as, refluxing temperature and time have been varied. Emphasis has been made on the sorption characteristics of inorganic ion exchangers for Fe(III) and Hg(II) metal removal from aqueous waste. Good thermal and chemical stabilities have also been observed for exchangers. Investigations have been made on the distribution coefficient (Kd) values for various metal ions. Distribution constants obtained for Fe(III) sorption on ZrSbW-III have been used in order to calculate the thermodynamic parameters like Gibb's free energy, change in enthalpy and entropy. This synthesized ZrSbW-III, three component system ion exchanger is proved to be a good sorbent for Fe(III) but shows less sorption for Hg(II). On the basis of sorption data, the Langmuir and Freundlich sorption isotherm models have also been confirmed. The separation factor (RL) revealed the favorable nature of the sorption process of metal ions sorption onto ZrSbW-III.

Research Highlights
► Present study deals with the hydrothermal synthesis and characterization of a new heteropolyacid salt; zirconium(IV) antimonotungstate.
► This work describes the sorption characteristics and stability studies of zirconium compound.
► Zirconium(IV) antimonotungstate seems to be a promising ion exchange material with a significant ion exchange capacity.
► The thermal stability of zirconium(IV) antimonotungstate was compared with that of other zirconium based ion exchangers and it was concluded that it has better resistance to heat.
► The prepared ion exchanger may proved to be the good candidate for the removal of iron metal.