[en] Graphical abstract: Magnetization curve of TMT-MRGO composite. - Highlights: • A novel magnetic composite TET-MRGO is prepared. • TET-MRGO is highly magnetic and can be easily separated from aqueous solution. • TET-MRGO shows excellent adsorption capacity for Cu(II) (209.1 mg g"−"1). • TET-MRGO shows excellent adsorption selectivity toward Cu(II). • The reusability of TET-MRGO is encouraging and hopeful for practical use. - Abstract: In the present paper a new type of triethylenetetramine-magnetite reduced graphene oxide (TET-MRGO) composite showing a high adsorption capacity (209.1 mg g"−"1) toward Cu(II) ions was prepared. The morphological, structural, and magnetic properties of TET-MRGO were characterized using infrared spectrometer, X-ray diffraction, Scanning Electronic Microscope, nitrogen adsorption–desorption measurement, Raman spectroscopy, and Transmission Electron Microscopy. TET-MRGO exhibits strong saturation magnetization (42.13 emu g"−"1) and can be easily separated from aqueous solution by an external magnetic field. A series of batch adsorption experiments were systematically conducted to study the adsorption property of TET-MRGO. The high adsorption capacity, excellent selectivity, and effective adsorption–desorption results indicated the prepared TET-MRGO composite could be an effective adsorbent for removing Cu(II) ions from aqueous solution.