Modification of CoFe2O4 Magnetic Nanoparticles by Dopamine and Ascorbic Acid as Anchors

CoFe2O4 magnetic nanoparticles were modified by dopamine (DA) and ascorbic acid (AA) as anchors. Separation of the DA and AA using CoFe2O4 magnetic nanoparticles have been studied by investigating the effects of pH, concentration of the DA and AA, amount of adsorbents, contact time, ionic strength and temperature. The mechanism of adsorption was also studied. The adsorption of DA and AA to the CoFe2O4 magnetic nanoparticles could be described by Langmuir-type adsorption isotherms. The effective surface area of the CoFe2O4 nanoparticles was 53.55 m2/g and 109.81 m2/g, respectively, for DA and AA. The maximum adsorption capacities were 28.98 and 72.99 mg of enediol per gram of adsorbent for DA and AA, respectively. With the help of adsorption isotherm, thermodynamic parameters such as free energy, enthalpy, and entropy have been calculated. The adsorption of DA onto CoFe2O4 is exothermic, but the temperature effect was negligible for adsorption of AA. On the basis of pseudo-first-order and pseudo-second-order kinetic equations different kinetic parameters have been obtained. DA and AA can be desorbed from the CoFe2O4 using concentrated imidazole as an eluent.