Abstract Separation of zirconium from uranium in carbonate media was undertaken by ion flotation. The collector chosen was octylhydroxamic acid (HOHX). It gave a well-flocculated precipitate with zirconium which floated in less than 5 min. The stoichiometry of the reaction is HOHX/Zr = 3.9/1, and the selectivity in the presence of uranium is very high. In fact, for a ratio ϕ [HOHX],M/(Zr),M, which is just stoichiometric and is close to 4, the zirconium removal rate reaches 99%, even in industrial media. The loss of uranium is only 0.5% although its concentration is 37.4g/L. Mechanisms of separation are not affected by a variation of pH between 6.7 and 9.8, of temperature up to 60°C, and of carbonate concentration within the 15 to 60 g/L Na2CO3 range.