Adsorption of Au(III) by amino-modified monodispersed PGMA microspheres and deposition of gold nanoparticles

Monodispersed poly(glycidyl methacrylate) (PGMA) microspheres with various amounts of amino groups (PGMA-NH₂) were used to adsorb Au(III) from simulated wastewaters. Gold nanoparticle-coated PGMA functional microspheres can be directly obtained via the adsorption process. The adsorption kinetics follows pseudo-second model, and 10 min is enough for reaching at equilibrium. The adsorption isotherm follows Langmuir model, and the adsorption amounts for Au(III) are 8.25 and 21.75 mol·kg⁻¹ at 298 and 328 K, respectively. The relative separation coefficients between Au(III), Pt(VI), Pd(II) and Co(II), Cu(II), Ni(II), Fe(III) are all higher than 100 when 1 < pH < 3. Furthermore, the characterization analysis of X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry (TG–DSC), scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) confirms that AuCl₄ ⁻ has been reduced to Au⁰ nanoparticles and deposited onto the surface of PGMA-NH₂. The current work shows a good prospect for PGMA-NH₂ to be a valid adsorbent for the recovery of gold and the possible fabrication of gold nanoparticles by reduction–deposition process without any reductant.