Facile synthesis of magnetic Fe3O4/CeCO3OH composites with excellent adsorption capability for small cationic dyes

Abstract

Magnetic Fe₃O₄/CeCO₃OH composites were prepared through a one-step hydrothermal route and their applications as adsorbents for removal of dyes were investigated. The as-prepared Fe₃O₄/CeCO₃OH composites as well as single component Fe₃O₄ and CeCO₃OH were characterized by XRD, TEM, FTIR, TG, XPS, EDX, Ar physisorption, and zeta potential analysis. Results showed that the composite of Fe₃O₄ with CeCO₃OH significantly improved the adsorption ability compared to both Fe₃O₄ and CeCO₃OH, and Fe/Ce dosage ratio was the key to control the adsorption properties of the adsorbents. The adsorption amount of the adsorbent was closely related to the amount of surface carboxylate groups, which exhibited surface negative charge and thus superior ability to adsorb cationic dyes. The weight percentages of surface carboxylate groups for the adsorbents with Fe/Ce dosage ratios of 5 : 0, 4 : 1, 1 : 1, 1 : 4 and 0 : 5 were 7.6%, 18.3%, 15.1%, 12.0% and 5.9%, respectively. The maximum adsorption capacity reached 666.2 mg g⁻¹ for methylene blue (MB) at the Fe/Ce dosage ratio of 4 : 1, much higher than other magnetic adsorbents. The kinetic adsorption data fitted the pseudo-second-order model and the isotherm data followed the Langmuir model. Besides, the magnetic property of the Fe–Ce composite made solid–liquid separation easily achievable. These results demonstrated that this composite material could be used as a good adsorbent for selective removal of small cationic dyes from wastewater, and this facile synthesis method can be used to prepare other high performance adsorbents.