Display omitted •The structural and photo-electrochemical properties of the new heterostructure of NiAl2O4 supported on Kaolin (10:90) prepared by the impregnation method were studied.•The adsorption was carried for methyl green dye solution (C0 = 50 mg/L) and the process was well described by Langmuir isotherm model.•The photocatalytic activity under the solar light irradiation was successfully tested for the degradation of methyl green dye.•The photocatalytic reaction mechanism of NiAl2O4/Kaolin was established regarding to the different characterizations carried out. Nanosized spinel NiAl2O4 was successfully supported on kaolin, natural support, by impregnation method; then tested as photocatalyst towards organic pollutant. The catalyst was characterized by IR spectroscopy, XR diffraction, BET, reflectance and XPS techniques. The photocatalytic tests were followed by UV–Vis spectroscopy for degradation of Methyl Green (MG) solution (C0 = 50 mg/L) under sunlight irradiation. The maximum adsorption (91.56 mg/g) of MG dye solution was observed for NiAl2O4 at an equilibrium time of 240 min; nevertheless, for NiAl2O4/kaolin, the equilibrium time was only 150 min for an adsorbed quantity equal to 45.78 mg/g. Some parameters influencing the dye adsorption were optimized. The fitting of the adsorption data for the Methyl green follows the Langmuir isotherm model. This new nanocomposite of NiAl2O4/kaolin exhibited excellent photocatalytic activity, which can degrade MG dye; mainly after adding the hole sensors (H2O2), within 90 min under sunlight irradiation.