Synthesis of an organic-inorganic polypyrrole/titanium(IV) biphosphate hybrid for Cr(VI) removal

•Successful synthesis of an organic-inorganic hybrid material PPy/Ti(HPO4)2 by oxidative polymerization reaction•High adsorption performance (1.67 mmol/g) of PPy/Ti(HPO4)2 for Cr(VI) removal•pH and ion strength dependent adsorption process•Endothermic and spontaneous adsorption process

An organic-inorganic polypyrrole/titanium(IV) biphosphate hybrid, PPy/Ti(HPO4)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(HPO4)2 hybrid was an endothermic and spontaneous process. These results suggested that the PPy/Ti(HPO4)2 hybrid might be a potential candidate for the separation of Cr(VI) from aqueous solution.

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