Nickel ferrites having different stoichiometry supported on activated carbon (Ni0.25Fe2.75O4-AC, Ni0.5Fe2.5O4-AC, NiFe2O4-AC) were prepared by co-precipitation using nitrate precursors and activated carbon from peach stones and calcination procedure in nitrogen atmosphere. The physicochemical properties of these materials were studied by powder X-ray diffraction analysis (PXRD) and Mössbauer spectroscopy. The presence of spinel ferrite and additional hematite phases was established by PXRD. The photocatalytic properties of the so synthesized nickel ferrite-AC materials were tested and compared in oxidative degradation of Malachite Green (MG) and Reactive Black 5 (RB5) dyes under UV-light irradiation. The photocatalytic tests show that investigated samples lead to much higher degree of degradation of MG (86%-92%) compared with that of RB5 (17%-35%) due to their structure. The results proved that nickel ferrite-AC materials are more efficient photocatalysts for removal of MG as model contaminant from aqueous solution under UV light than RB5.