Magnetic beads for cadmium removal from human plasma in magnetically stabilized fluized bed (MSFB)

The aim of this study is to prepare ion-imprinted magnetic beads which can be used for the selective removal of Cd2+ ions from Cd2+-overdosed human plasma. N-methacryloyl-(L)-cysteinemethylester (MAC) was chosen as the complexing monomer. In the first step, Cd2+ was complexed with MAC and the Cd2+-imprinted magnetic poly(HEMA-MAC) (mMIP) beads were produced by suspension polymerization in the presence of magnetite Fe3O4 nano-powder. After that, the template ions (i.e., Cd2+) were removed from the polymer matrix using 0.1 M thiourea solution. The specific surface area of the mMIP beads was found to be 24.7 m2/g with a size range of 63-140 µm in diameter and the swelling ratio was 70 %. The average Fe3O4 content of the resulting mMIP beads was 8.2 %. According to the elemental analysis results, the beads contained 41.8 µmol MAC/g polymer. The Cd2+ adsorption capacity decreased drastically from 48.8 µmol/g to 20.0 µmol/g with the increase of the flow rate from 0.50 ml/min to 3.0 ml/min. The maximum adsorption capacity was 48.8 µmol Cd2+/g beads. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherm and isotherm constants. Equilibrium data fitted very well to the Langmuir model in the entire concentration range (5-200 mg/L). The pseudo-first order and pseudo second order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The results showed that adsorption process of Cd2+ ions onto mMIP beads followed the pseudo second-order kinetic model. The relative selectivity coefficients of mMIP beads for Cd2+/Pb2+ and Cd2+/Zn2+ were 22.6 and 160.7 times greater than non-imprinted (mNIP) beads, respectively. The mMIP beads could be used many times without decreasing their adsorption capacities significantly.