Facile self-assembly of Au nanoparticles on a magnetic attapulgite/Fe3O4 composite for fast catalytic decoloration of dye

Abstract

In this paper, we employed a simple and efficient electrostatic self-assembly strategy to fabricate superparamagnetic attapulgite/Fe₃O₄/Au nanoparticles (APT/Fe₃O₄/AuNPs) nanocomposites with a well-dispersed distribution of AuNPs using natural chitosan (CTS) as a “bridge”. The “toruloid” APT/Fe₃O₄ composite with negative surface charges was firstly prepared by a one-step solvent-thermal reaction between APT, FeCl₃ and ethylene glycol, and then the positively charged CTS was used as a “double sided tape” to tightly adhere APT/Fe₃O₄ and AuNPs through electrostatic interaction. UV-vis, XRD and TEM analyses proved that the “toruloid” structure was formed, and AuNPs were successfully attached on the APT surface with good dispersion. The formation of the “toruloid” composite structure can not only bring stronger magnetism, but also facilitate the attachment of AuNPs. The APT/Fe₃O₄/AuNPs nanocomposite shows excellent catalytic activity, which can rapidly catalytically decolor a solution of Congo red (20 mg L⁻¹) within 2 min at a low dosage of 0.3 g L⁻¹. In addition, the nanocomposite shows strong magnetism with a maximum magnetization rate of 33.6 emu g⁻¹. This makes the nanocomposite prone to be magnetically separated and recycled.