In this study, quaternary MgY2O5@g-C3N4 nanomaterials were produced using a simplistic ultrasonic power technique in the presence of an organic solvent, and their capability to abolish Cu (II) from an aqueous solution was evaluated. As validated by powder X-ray diffraction, the synthesized nanomaterials possessed excellent crystallinity, purity, and tiny crystalline size. According to BET and TEM, the nanomaterials with high porosity nanosheets and perfect active sites made Cu (II) removal from water treatment feasible. At a pH of 3.0, the MgY2O5@g-C3N4 displayed good Cu (II) adsorption capability. The Cu (II) adsorption adhered to the Langmuir adsorption model, with an estimated theoretical maximum adsorption aptitude of 290 mg/g. According to the kinetics investigation, the adsorption pattern best fitted the pseudo-second-order kinetics model. Depending on the FTIR results of the nanocomposite prior to and after Cu (II) uptake, surface complexation and ion exchange of Cu (II) ions with surface hydroxyl groups dominated the adsorption of Cu (II). The MgY2O5@g-C3N4 nanomaterials have great potential as adsorbents for Cu (II) removal due to their easy manufacturing process and high adsorption capacity. Additionally, the reuse of MgY2O4@g-C3N4 nanomaterials was tested through the succession of four adsorption cycles using HNO3. The result showed the good stability of this material for mineral pollution removal.