Two different methods were employed to synthesis NiO/C composite from agricultural waste. The mesoporous composite was successfully synthesized via a novel precipitation method in the presence of dissolved gases. The morphology of the composites were differentiated by characterisation techniques such asx-ray Diffraction (XRD), the point of zero charge (pHpzc), field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive x-ray analysis (EDAX) and vibrating sample magnetometer (VSM). Then, the mechanism of synthesis was elucidated using the above experimental characterisation data. FESEM and EDAX report of Ni(OH)2-carbon composite clearly showed the role of dissolved gases on synthesis. Both the composites were subjected as the adsorbent to eliminate/remove the toxic Pb(II) ions from the wastewater. Batch adsorption experiments were carried out to compare the Pb(II) ions removal capability of both the composite materials. The parameters such as the effect of pH, the dosage of the adsorbents and initial concentration were studied. At the optimized conditions, isotherm studies for each of the adsorbents were also carried out. The isotherm results revealed that the maximum removal capacity qe (mg/g) was 30.78 for PJNC and 43.48 for PJGNC. The VSM analysis confirmed that both the adsorbents were soft magnetic materials. Hence, they could be competently separated from salted/treated water using the magnetic field.