At the temperatures of 25 °C, 35 °C and 45 °C, all the obtained adsorption
data were better accorded with the Freundlich isotherm
model (R2 = 0.9946, 0.9939, 0.9966) (Table 2). These facts indicated
that Cu2+ was unevenly adsorbed in the form of monolayer coverage
on the surface of adsorbent. 0 b 1/n b 0.5 indicated that copper ion
was facile to be adsorbed on MgHAp/Fe3O4 [49]. Meantime, the results
also showed that the maximum adsorption capacity could reach to
333 mg/g and augment along with the increase of temperature.
3.5. Adsorption thermodynamics
Adsorption thermodynamics showed the energy effects in the process
of adsorption, which could reflect whether an adsorption process
could take place under certain conditions and temperature. The adsorption
thermodynamics studies were carried out at different temperatures