A novel magnetic nano-composite was synthesized by a simple method of coprecipitation through embedding
ferroferric oxide into magnesium hydroxyapatite (MgHAp/Fe3O4) to remove Cu2+ from aqueous solution. The obtained
adsorbent was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS),
Brunauer–Emmett–Teller (BET) surface area measurement and Fourier transform infrared spectroscopy (FTIR).
Mg2+ and Cu2+ possess the same electrical charge and similar ionic radius, which is especially beneficial to their
exchange in hydroxyapatites. Static adsorption experiments indicated that the maximal immobilization capacity
of Cu2+ reached to 305 mg/g on the optimum adsorption conditions (dosage of 0.32 mg/mL, contact time for
90 min, pH at 5.9 and temperature at 25 °C). Adsorption kinetics including the pseudo-first order and pseudosecond
order kinetic models were researched and the data fitted better with the pseudo-second order kinetic
model (R2 = 0.99). For adsorption isotherms, Freundlich isotherm was proved to be the best correlation (R2
N 0.99) compared with the Henry and Langmuir isotherms. The thermodynamic parameters (ΔG b 0, ΔS =
43.38 J/mol/K, ΔH = 7.006 kJ/mol) indicated that it was a spontaneously endothermic reaction. Furthermore,
the well anti-interference and stability properties of the MgHAp/Fe3O4 adsorbent were confirmed through the
interference experiment of coexistent metal cations and desorption experiment, respectively.