2.4. Static adsorption studies
All of synthetic solutions were prepared by diluting copper solutions
(1000 ± 1 mg/L) obtained by dissolving Cu(NO3)2 into demonized
water. Fresh dilutions were used in each experiment.
In order to determine the optimum Cu2+ adsorption conditions, batch
adsorption experiments were carried out with a certain amount of
MgHAp/Fe3O4 nanospheres and 25 mL of Cu2+ solutions (100 mg/L) in
a series of 100 mL conical flasks. The effect of dosage (MgHAp/Fe3O4)
was tested in the range of 2–20 mg (natural pH, contact time for 3 h,
temperature at 25 °C). Other adsorption conditions were conducted
like this. The effect of contact time was studied in the time range of 2–
120 min (dosage of 8 mg, natural pH, temperature at 25 °C) and the effect
of pH was investigated at pH in the range of 1–7 (dosage of 8 mg,
contact time for 90 min, temperature at 25 °C). Furthermore, batch
equilibrium isotherms studies on MgHAp/Fe3O4 were conducted with
a range of different concentrations of Cu2+ solutions by contacting a
constant mass (8 mg) of MgHAp/Fe3O4 for 90 min at 25 °C, 35 °C and
45 °C respectively. At the end of the adsorption process, adsorbent
was separated from the solution by magnetic separation and supernatant
was analyzed for surplus Cu2+ concentration by spectrophotometric
method. The adsorption capacity of MgHAp/Fe3O4 and the
removal rate of Cu2+ were computed using the following equations