[en] Highlights: • Hierarchical structured Fe₂O₃ microspheres were successfully fabricated using acid leachate of ilmenite as precursor. • A possible formation mechanism was proposed for the hierarchical structured Fe₂O₃ microspheres. • Compared with most reported adsorbents, the Fe₂O₃ microspheres exhibited excellent removal performance for dyes. • Removal mechanism mainly included ion exchange, electrostatic adsorption and pore filling. • This work provided a novel approach for “waste eliminates waste, turning waste to treasure”. A facile method using acid leachate of ilmenite as the precursor has been successfully developed to tailor the structure of Fe₂O₃. The morphology and structure of the final product can be controlled from nanoparticles, microcubes, rhombohedrons to microspheres by varying the synthetic parameters. Detailed characterization showed that the microspheres had a hierarchical structure and was actually consisted of nanoblocks subunits. A possible mechanism was proposed for the formation of the hierarchically structured Fe₂O₃ microspheres. Due to its large surface area and abundant functional groups, the Fe₂O₃ microspheres could efficiently remove organic dyes in aqueous solution. The measured maximum adsorption capacities were 723.8, 150.7, and 54.5 mg/g for Congo red, Methyl orange, and Methylene blue, respectively, which were generally higher than those for Fe₂O₃ with other structures reported in literature. This work provides a novel approach to using waste as the resource for the preparation of low-cost and efficient adsorbent materials.

[en] Three different morphologies of FeTiOx materials (microcubes, etched-microcubes and microspheres) were prepared by a facile method using acid leachate of ilmenite as the precursor. The three FeTiOx materials exhibited different adsorption performance for Congo red (CR). Among them, the FeTiOx microspheres showed the highest adsorption capacity (723.8 mg/g) for CR, followed by the FeTiOx etched-microcubes (617.8 mg/g) and the FeTiOx microcubes (296.5 mg/g). Characterization results showed that the three FeTiOx materials had distinctive phase composition, pore structure and surface functional group, which ultimately lead to their difference in adsorption performance. The adsorption mechanism of the three FeTiOx materials mainly includes ion exchange, electrostatic adsorption and mesopore filling, but the contribution of each type is different.

[en] Highlights: • Ni3Al-HTO showed higher activity than Ni3Fe-HTO and Ni3Cr-HTO in COS removal. • The effects of trivalent ions on the phy-chemical property of HTO have been studied. • Precise chemical state of the HTO was studied by Ni K-edge XANES spectra and DFT. • Preferable activity was ascribed to the high reduction of Ni²⁺ on Ni3Al-HTO.