<p>There are serious concerns for the environment and public health when there is an excessive amount of nitrate in water sources due to industrial effluents and agricultural runoff. This work examines the possibility of biochar nanoparticles as an effective and sustainable material for nitrate removal from polluted water. In the current study, the metal-doped nanoparticles supported biochar were synthesized in order to remove nitrate from contaminated water. The biochar was synthesized through pyrolytic treatment at 600˚C for 2&#xa0;h. The nanoparticles were synthesized using a bottom-up approach and further doped with biochar to prepare BC@RHCoNps, BC@RHFeNps, and BC@RHMnNps. The surface morphology of BC@RHCoNps was studied using FESEM, and the surface functionality was also observed using Fourier Transform Infrared Spectroscopy (FTIR) before and after the adsorption of nitrate. The particle size of nanoparticles was analysed using Dynamic Light Scattering (DLS). Moreover, comparative observation of X-Ray diffraction (XRD) of the above nanoparticles doped biochar was used to study the physical properties of the material. The impact of different parameters such as catalyst dosage, initial concentration, contact time, and pH was compared in all the three synthesized biochars. The cobalt nanoparticle has a smaller particle size as compared to iron and manganese nanoparticles, as a result, BC@RHCoNps showed maximum removal efficiency. The BC@RHCoNps showed the best removal efficiency of 92.51%, followed by BC@RHFeNps at 91.13% and BC@RHMnNps of 89.21%, with the initial concentration of 100&#xa0;mg L ⁻¹, catalyst dosage of 100&#xa0;mg, at pH = 6.28 with a reaction time of 60&#xa0;min at 25&#xa0;°C under 180&#xa0;rpm of rotation. The above findings showed that BC@RHCoNps proved to be the best adsorbent for the removal of nitrate from contaminated water.</p>