Eliminating the hazardous dyes from the wastewater is essential for the sustainable furtherance of eco-friendly-oriented industrial growth. The untreated effluents containing dyes can damage the ecosystem and cause serious health issues to humans, animals, and aquatic species. In the present work, the multi-wall carbon nanotubes (MWCNTs) were functionalized using the combination of sulphuric acid and nitric acid. These functionalized multi-wall carbon nanotubes (F-MWCNTs) were characterized using Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray analysis (EDAX) to confirm the presence of functional groups. The catalytic dye degradation efficiency of pristine multi-wall carbon nanotubes (P-MWCNTs) and F-MWCNTs was tested for methylene blue (MB), and indigo carmine (IC) dyes under dark and ultraviolet (UV) light exposure conditions. F-MWCNTs have exhibited appreciable degradation efficiency (similar to 90%) under dark and UV light compared to P-MWCNTs. An increment in efficiency was observed for UV-light-aided dye degradation. The impact of pH and temperature on degradation was analyzed in detail. The reaction kinetics was studied to determine the rate constants of the degradation reactions. A substantial quantum efficiency (QE) enhancement was noticed for F-MWCNTs compared to P-MWCNTs for both MB and IC degradation.