Shape-controlled synthesis of α-Fe2O3 nanocrystals for efficient adsorptive removal of Congo red

Abstract

A facile solvothermal reaction was developed to synthesize α-Fe₂O₃ nanocrystals at relatively low temperature in the presence of small organic compound 2,4,6-tris(pyrazol-1-yl)-1,3,5-triazine (Tptz) as template. α-Fe₂O₃ nanocrystals with three different morphologies were obtained by simply changing the volume ratio of the reaction solvents, N,N-dimethylformamide (DMF) and H₂O. The purities and morphologies of these samples were characterized by powder X-ray diffraction (PXRD), infrared spectrum (IR), high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). It is remarkable that both the template Tptz ligand and the volume ratios of the mixture solvents are playing very significant roles for the formation and the morphological control of the products in this work. Furthermore, Congo red adsorption experiment showed that the adsorption capacities increased in an order of the samples with morphologies of nanopolyhedra, nanorods and rice-shaped. And the determined maximum adsorption capacity is up to 161 mg g⁻¹ for the rice-shaped α-Fe₂O₃, which has the biggest BET surface area of 110.2 m² g⁻¹. These α-Fe₂O₃ nanocrystals reported here may have the potential to use as low-cost and efficient adsorbent materials to remove organic pollutants from water.