Preparation of a polyelectrolyte-coated magnetic attapulgite composite for the adsorption of precious metals

By the layer-by-layer self-assembly of chitosan and cysteine modified beta-cyclodextrin on the surface of Fe3O4 nanoparticle-decorated attapulgite, the polyelectrolyte-coated magnetic attapulgite composite (Fe3O4/ATP@(CS/Cys-beta-CD)(8)) was prepared for the adsorption of precious metals. The as-synthesized Fe3O4/ATP@(CS/Cys-beta-CD)(8) composite was characterized by zeta potential measurements, Fourier transform infrared spectroscopy, X-ray diffraction and vibrating sample magnetometry. The Fe3O4/ATP@(CS/Cys-beta-CD)(8) composite has an adsorption yield of about 90% for Ag+, 90% for Pd2+ and 60% for Pt4+. Moreover, it was found that the adsorption of Ag+ and Pd2+ was preferential to that of Pt4+. The results of X-ray photoelectron spectroscopy indicated that the precious metals accept electrons provided by the N, O or S atoms of the Fe3O4/ATP@(CS/Cys-beta-CD)(8) composite during the process of adsorption. Therefore, the Fe3O4/ATP@(CS/Cys-beta-CD)(8) composite is a promising recyclable and low-cost adsorbent for the adsorption of trace precious metal ions.