Designing a stable and efficient adsorbent for removal of pollutants such as dyes is of serious concern nowadays. In view of that, magnetic cobalt oxide nanoparticles (CONP) were synthesized in a multigram scale using a modified self-propagator combustion method triggered by sucrose as the fuel. The material was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetism (VSM), scanning electron microscopy (SEM)-energy-dispersive system, high-resolution transmission electron (HRTEM), pH(ZPC), and Brunauer-Emmet-Teller surface area. SEM and HRTEM images confirm the presence of distinct pore channels. Room temperature VSM reveals weak hysteresis, indicating that the CONP is a soft but robust magnetic material. pH(ZPC) was found to be 6.45. Removal of malachite green from simulated water was tested in a batch mode and found to be promising. Physiochemical parameters such as pH, contact time, dose, and temperature were optimized. The maximum Langmuir adsorption capacity was found to be 238.10 mg/g. Adsorption is best described by the Langmuir isotherm model (R-2 = 0.999) and pseudo-second order kinetics (R-2 = 0.999). Regeneration (83%) with dilute acid enables its successive use. Its magnetic nature facilitates the rapid separation of the CONP after adsorption using a hand-held magnet. Easy synthetic protocols, robustness, high removal efficiency, and reusability make the material an ideal future choice for dye detoxification.