where qe is the amount of Cu2+ adsorbed per unit amount of adsorbents
when the adsorption reached equilibrium (mg/g), C0 and Ce
are the Cu2+ concentration in solution before and after adsorption,
respectively (mg/L), V is the bulk of the medium (mL) and m is the
dosage of MgHAp/Fe3O4 used in the reaction mixture (g).