Efficient removal of Mo(VI) ions via adsorbing colloid flotation based on the synergic effect of metal salts and CTAB

Abstract

Treatment of molybdenum-containing wastewater is crucial for mitigating the environmental threat of Mo(VI) ions and recovering valuable metals. Compared to conventional separation methods, adsorbing colloid flotation emerges as a viable way to efficiently remove Mo(VI) ions. However, the current colloidal adsorption reagents have constrained the development of adsorbing colloid flotation due to their poor removal efficiency and narrow solution pH range. To overcome these challenges, Zr(IV) salts and La(III) salts were employed as colloidal adsorption reagents for the first time to remove Mo(VI) ions from wastewater in this work. In particular, the differences in removal efficiency of Mo(VI) ions between Zr(IV) salts, La(III) salts and traditional Fe(III) salts were systematically evaluated over a wide solution pH range. Zr(IV) salts demonstrated robust pH stability, displaying a significant removal efficiency of over 70.00% for Mo(VI) ions during the colloidal adsorption stage across a broad solution pH range from 3 to 11. Even more astonishingly, the removal efficiency of Mo(VI) ions was further enhanced through the synergistic effect of cetyltrimethylammonium bromide (CTAB) during the flotation separation stage. Under the optimal conditions of bubble flotation, the solution turbidity decreased rapidly from 164.50 NTU to 3.33 NTU, and the removal efficiency of Mo(VI) ions reached an impressive 99.10% which was enhanced by 23.73% compared to the colloidal adsorption stage. In conclusion, Zr(IV) salts, serving as colloidal adsorption reagents, have overcome the limitations of traditional colloidal adsorption reagents and exhibit significant potential for the removal of Mo(VI) ions from wastewater.