Removal of uranium (VI) from acidic aqueous solutions by ion flotation using colloidal gas aphrons (CGAs)

Treatment of uranium-containing wastewater has become an increasingly important research focus with the exploitation and utilization of uranium resources. The introduction of new technologies and continuous updating of existing technologies are the urgent tasks for the treatment of uranium-containing wastewater. Ion flotation is one technology with the potential to address uranium contamination. In this study, the improved ion flotation technique for removing U(VI) from acidic solutions was established by colloidal gas aphrons (CGAs). The CGAs were produced by stirring cetyltrimethylammonium bromide (CTAB) solutions at high speed. Measurements of half-life, gas hold-up, bubble size distribution and zeta potential of CGAs have been performed in this work. In the batch process, as CGAs continued to be added, the uranium removal increased steeply at first then slowly, and finally leveled off. At pH 6, the final uranium removal can reach the highest 99.3 % at an initial uranium concentration of 2.5 mg/L. The effective removal of U(VI) by the CGAs formed by cationic CTAB indicated that U(VI) existed as anionic species under these conditions. It was found that the concentration of carbonate ions in solution increased with the increase of flotation time, which may be caused by the dissolution of carbon dioxide brought in by bubbles. The calculation results of Visual MINTEQ software show that the concentration of carbonate ions generated at pH 6 is sufficient for anionic uranium-carbonate to dominate. In addition, it was found that the size and zeta potential of CGAs all played a significant role in removing U(VI) from the acidic solution.