<p>This study examines the impact of the composition, texture and structure of sodium- and calcium-rich bentonite clays further exchanged with cobalt cations and then combined with a polyaniline-type polymer, with the aim of obtaining an efficient photocatalyst for the degradation of methyl orange azo dye in wastewater under natural sunlight irradiation. The structural, textural and optical properties, as well as the differences between the resulting nanostructures were evaluated using X-ray diffraction, UV–Visible and infrared spectroscopy, scanning electron microscopy coupled to energy-dispersive spectroscopy, and nitrogen physisorption. The photocatalytic activity enhancement observed on the nanocomposites has been attributed mainly to their lower band gap energy (<i>E</i>_g = 2.31&#xa0;eV for polyaniline/cobalt-modified purified calcium bentonite clay (PAn/Co-PBC-c) and <i>E</i>_g = 2.14&#xa0;eV for polyaniline/cobalt-modified purified sodium bentonite clay (PAn/Co-PBC-s)), enhancement of visible light absorption, less recombination of electron–hole induced by incorporation of bentonite modified with cobalt cations, surface heterogeneity and more open porosity, resulting in methyl orange photodegradation rates of 31.5% and 27.6%. The kinetic studies revealed distinct photodegradation kinetic behavior with a pseudo-first&#xa0;order characterized PAn/Co-PBC-c, whereas PAn/Co-PBC-s agrees with second order kinetics. Such differences have been explained through the comparison of their texture and structure which led to the conclusion that the improved interface obtained on the first catalyst can be the result of enhanced exfoliation process during the composite’s preparation leading to more uniform physicochemical properties and improved interface between PAn and Co-PBC that would promote electron transport to form reactive intermediate species in the photocatalytic process degradation.</p> Graphical abstract <p></p>