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

Abstract

By the layer-by-layer self-assembly of chitosan and cysteine modified β-cyclodextrin on the surface of Fe₃O₄ nanoparticle-decorated attapulgite, the polyelectrolyte-coated magnetic attapulgite composite (Fe₃O₄/ATP@(CS/Cys-β-CD)₈) was prepared for the adsorption of precious metals. The as-synthesized Fe₃O₄/ATP@(CS/Cys-β-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-β-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-β-CD)₈ composite during the process of adsorption. Therefore, the Fe₃O₄/ATP@(CS/Cys-β-CD)₈ composite is a promising recyclable and low-cost adsorbent for the adsorption of trace precious metal ions.