A Novel Bio-adsorbent of CoFe2O4@SiO2 Core-Shell Nanoparticles Modified with Persimmon Tannin for Simultaneous Au(III) Ions Adsorption and Reduction

A novel bio-adsorbent was synthesized by the reaction between persimmon tannin (PT) and cobalt ferrite (CoFe2O4) with glutaraldehyde crosslinking, assigned as CoFe2O4@SiO2@PT. The product structure was confirmed by FTIR, XRD, TEM, DSC/TGA, and VSM. The results confirmed that the adsorbent had been successfully prepared and its surface had hydroxyl groups, which gave a great active site for Au(III) adsorption. As tested by batch system results, the kinetic data were consistent with the pseudo-second-order equation, while the adsorption equilibrium data fit well with the Langmuir model. The competitive adsorption test indicated that the adsorbent had a good preference to adsorb Au(III) over other coexisting ions. The Au(III) adsorption capacity of the adsorbent was 881.91 mg/g. It is greater than that of the reported adsorbents. The characterization by XRD, EDX, and SAED suggested that the adsorbed Au(III) was reduced to Au(0) particles as facilitated by the available functional groups. This adsorbent may be one of the good choices for the preconcentration and recovery of Au(III) from e-waste.