Optimization of Copper(II) Adsorption onto Novel Magnetic Calcium Alginate/Maghemite Hydrogel Beads Using Response Surface Methodology

Magnetic calcium alginate hydrogel beads (m-CAHBs, 3.4 mm average diameter) composed of maghemite nanoparticles and calcium alginate were prepared and characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX). The response surface methodology was used to model and optimize the adsorption removal of Cu(II) from aqueous solution by m-CAIBs. Adsorption experiments were also carried out to examine the effect of three parameters, such as pH (2.0-6.0), adsorbent dosage (2.0-6.0 g L-1) and initial Cu(II) ion concentration (250-750 mg L-1). Maximum percent removal was attained under the optimum conditions with pH 2.0, 2.0 g L-1 adsorbent dosage for 250 mg L-1 initial Cu(II) ion concentration. The amount of Cu(II) adsorption after 6 h was recorded as high as 159.24 mg g(-1) for 500 mg initial Cu(II) ion concentration. The adsorption kinetics indicated that the adsorption process was better described by the pseudo-second-order kinetic model. Desorption experiments indicated that the adsorption mechanism of Cu(II) occurred preferentially more by chelation than by electrostatic interaction. The percent removal of Cu(II) on m-CAHBs could still be maintained at 73% level at the fifth cycle.