Competitive adsorption of strontium and cobalt onto tin antimonate

Radioactive strontium (90Sr) and cobalt (60Co) are two major contaminants in low-level radioactive wastewaters from nuclear power plants. In this study, a tin antimonate sorbent (SnSb) used to simultaneously remove Sr and Co was prepared via a new and safe method. The as-prepared SnSb consisted of a composite structure of both pyrochlore and rutile microcrystal dispersed homogeneously at the nanometer scale. The sorbent had a good affinity to both Sr(II) ions and Co(II) ions across a wide pH range of 2-12 or in the presence of various non-radioactive ions. The adsorption competition performance of Sr(II) and Co(II) was investigated, with the adsorption isotherms following the extended Freundlich multicomponent isotherm and Sheindorf-Rebuhn-Sheintuch equation. Although Co(II) was more readily adsorbed on the sorbent, Sr(II) clearly inhibited Co adsorption. The kinetic performance of Sr(II) and Co(II) was described well by a pseudo-second order equation. When compared to the single-component adsorption, the adsorption rate of Sr(II) with Co(II) in the binary-component system decreased due to a competitive adsorption process.