This book describes the removal of Malachite Green (MG) dye by Bentonite and Bentonite-Lanthanum Oxide nanocomposites were investigated. Lanthanum oxide nanoparticles were prepared by Precipitation method and Bentonite-Lanthanum oxide nanocomposites were prepared by impregnation method. Bentonite and synthesized Bentonite-Lanthanum Oxide nanoparticles composites were characterized by FTIR spectroscopy, X-ray diffraction (XRD), Field emission gun scanning electron microscopy (FEG-SEM)with EDS spectra and High-resolution transmission electron microscopy (HR-TEM) for surface morphological and crystalline size determination. This explains the photocatalytic degradation of Malachite Green dye was measured by visible absorption spectroscopy using Bentonite and Bentonite-Lanthanum oxide nanocomposites. To obtain the optimal conditions for the dye degradation, the effect of various experimental parameters, like the amount of adsorbents, pH, concentration of dye, contact time and light intensity on the rate of reaction was studied.