Magnetic nanoparticles coated with mixtures of sodium oleate and saponified 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester were prepared as a kind of adsorbent for magnetically assisted chemical separation of copper ions. The extraction behavior was investigated using equilibrium batch experiment. The results demonstrated that mixtures of sodium oleate and saponified 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester had an evident synergistic effect on the copper extraction. The adsorption isotherm followed the Langmuir model, and the maximum sorption capacity of Cu(H) was 24.2 mg/g. The sorbent was highly selective toward Cu(II) at equilibrium pH 6.5, while the extraction of other metal ions was quite low in the binary solution systems. Artificial wastewater was prepared for selective removal of Cu(II) at the optimal experiment conditions. Desorption could be achieved using a 0.01 mol/L HCl eluent. The synergistic extraction mechanism of copper was confirmed to be ion exchange and surface complexation through pH analysis, Fourier transform infrared (FUR), and X-ray photoelectron spectroscopy (XPS) techniques.