Green Synthesis of Persimmon Tannin Modified With CoFe2O4@SiO2 Nanoparticles for Au(III) Ions Adsorbent: Synthesis Optimization and Characterization

Abstract

Persimmon tannin (PT) was immobilized onto CoFe₂O₄@SiO₂ microspheres to create a novel core–shell nanostructured magnetic bioadsorbent. The as-designed CoFe₂O₄@SiO₂@PT was used to recover Au(III) ions. The bioadsorbent synthesis was performed with different reaction times of 2, 4, 6, 12, and 24 h with a PT to magnetic core weight ratio of 0.8, 1.0, 1.2, 1.5, and 2.0. The profile of Au(III) adsorption by the material in aqueous medium was investigated in a batch system. XRD, FTIR, TEM, thermal analysis, and VSM were used to analyze the materials. The adsorption experiments were conducted in a pH 5 medium, with an adsorbent weight of 5.0 mg and an Au(III) ion concentration of 200 mg/L. The XRD shows that the material is crystalline and retains its structure during the modification. The FTIR data suggest that the material contained expected functional groups. As indicated by the VSM data, it maintains magnetic properties with a range of 12.76 to 17.45 emu/g. The Au(III) adsorption mechanism by the CoFe₂O₄@SiO₂@PT adsorbent was realized by electrostatic interaction and complex formation followed by the reduction of the ions. The maximum Au(III) adsorption capacity was recorded to be 393.34 mg/g.