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An organic–inorganic polypyrrole/titanium(IV) biphosphate hybrid, PPy/Ti(HPO 4 ) 2 , was successfully synthesized by oxidative polymerization and applied to remove Cr(VI) from aqueous solutions. The as-prepared organic–inorganic hybrid was characterized by scanning electron microscope, X-ray diffraction, zeta potential analysis and X-ray photoelectron spectroscopy. The adsorption conditions, such as contact time, pH value and ionic strength, were investigated, indicating a pH and ionic strength dependent adsorption process. The adsorption kinetics fitted well with the pseudo-second-order kinetic model and the equilibrium data can be described by the Langmuir isotherm with a maximum adsorption capacity of 1.67 mmol/g at pH = 3.5 ± 0.1 and T = 288.15 K. Thermodynamic parameters calculated from the temperature-dependent adsorption isotherms suggested that the adsorption of Cr(VI) on PPy/Ti(HPO 4 ) 2 hybrid was an endothermic and spontaneous process. These results suggested that the PPy/Ti(HPO 4 ) 2 hybrid might be a potential candidate for the separation of Cr(VI) from aqueous solution. [ABSTRACT FROM AUTHOR]

Highlights: [•] Amidoxime-functionalized silica coated Fe3O4 was synthesized and characterized. [•] Fe3O4@SiO2-AO exhibited fast and efficient sorption for U(VI). [•] Fe3O4@SiO2-AO could be easily separated from aqueous solutions with a magnet. [•] Fe3O4@SiO2-AO was resistant to acid corrosion. [•] U(VI)-loaded Fe3O4@SiO2-AO could be efficiently regenerated and reused. [Copyright &y& Elsevier]