Currently, there is great interest in the use of TiO for photocatalytic remediation of wastewater. Doping, heterojunction, and immobilization on porous materials are effective methods to improve the photocatalytic efficiency of this semiconductor oxide. In this study, ZnTiO/TiO (ZTO) and ZnTiO/TiO/La (ZTO/La) nanocomposites were successfully prepared and immobilized on diatomaceous earth (DE). The composition and texture of the composites prepared were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM-EDX), and specific surface area (SSA). The adsorption capacity and photocatalytic activity of the composites were determined via degradation of methylene blue (MB) in batch reactors. The materials evaluated were prepared in the shape of 0.2 cm (diameter) and 1.0 cm (length) cylindrical extrudates. The results indicate that the ZTO/La-DE composite exhibited higher efficiency for the removal of MB under solar irradiation than both ZTO-DE and DE. The pseudo-second-order model and the Langmuir isotherm model were better suited to explain the adsorption process. The highest degradation percentage of MB obtained was 96% after 150 min of irradiation. The results indicate that synthesized composite could be used for the removal of cationic dyes in wastewater.