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• BiFe 1-x Ni x O 3 were obtained by high-energy ball milling assisted by annealing. • BiFe 1-x Ni x O 3 (x ≤ 0.40) powders show photocatalytic activity under visible light. • The photocatalytic activity of BiFe 1-x Ni x O 3 is higher than TiO 2 under visible light. • BiFe 0.9 Ni 0.1 O 3 shows the highest removal efficiency. • BiFe 1-x Ni x O 3 are novel magnetically recoverable visible-light photocatalysts. In this study, the photocatalytic activity of bismuth ferrite (BiFeO 3) that is modified with Ni2+ to obtain BiFe 1-x Ni x O 3 (0 ≤ x ≤ 0.4 mol) is reported. The powders were synthesized by assisted high-energy ball milling. The X-ray diffraction (XRD) and Rietveld refinement demonstrate that Ni2+ cation is introduced in small quantities into the BiFeO 3 crystal structure and occupies Fe3+ sites. The excess nickel transforms the BiFeO 3 into sillenite (Bi 25 FeO 40) and nickel ferrite (NiFe 2 O 4) phases. The photocatalytic activities of the BiFe 1-x Ni x O 3 samples were compared to that of a commercial titanium dioxide (TiO 2 -P25) photocatalyst. Under irradiation in the UV–vis light spectrum, TiO 2 -P25 showed the highest photonic efficiency. The result was opposite when the samples were irradiated in the visible spectrum, where all the synthesized samples exhibited higher removal of crystal violet dye than those that were treated with the TiO 2 -P25. According to the results, all the modified materials are magnetically recoverable photocatalysts. [ABSTRACT FROM AUTHOR] more...