A magnetic graphene oxide nanocomposite modified by the ionic liquid 1-amino-3-methylimidazole chloride (LI-MGO) was prepared by the chemical coprecipitation method as a phenol adsorbent for the treatment of contaminated aqueous environments. The structure of the prepared nanocomposite was investigated using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transient electron microscopy. The prepared nanoparticles exhibited a BET specific surface area of 110.44 m2 g−1 and total pore volume of 0.2839 cm3 g−1. The results revealed that the adsorption process had the highest phenol removal percentage (95.3%) under optimum conditions (pH = 3, nanocomposite concentration = 0.04 g/l at room temperature). Kinetic studies showed a significant fit to the pseudo-second-order kinetic model (R2 > 0.9997) giving an equilibrium rate constant (K2) of 0.000119 gmg−1 min−1 for phenol loaded. The experimental adsorption data were better fitted with the Langmuir isotherm model than with the Freundlich isotherm model. To further investigate the phenol removal optimization process of the modified magnetic nanoparticles, and to determine the effect of each parameter on the adsorption process, the Taguchi optimization approach was used. The adsorption of these synthesized nanocomposites is among the low-cost, high-efficiency processes that can be used for the reduction/elimination of environmental pollutants, especially in aqueous environments.