Extraction and determination of trace amounts of gold(III), palladium(II), platinum(II) and silver(I) with the aid of a magnetic nanosorbent made from Fe3O4-decorated and silica-coated graphene oxide modified with a polypyrrole-polythiophene copolymer

The authors describe the synthesis of a nanosorbent for fast magnetic solid phase extraction of trace levels of Ag(I), Au(III), Pd(II) and Pt(II). It consists of graphene oxide sheets modified with magnetite nanoparticles (mGO) coated with silica. This material was further modified with a polypyrrole-polythiophene copolymer via oxidative polymerization to end up with a material of the type mGO@SiO2@PPy-PTh. Successful synthesis of the nanocomposite and its components was corroborated by FT-IR, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and thermogravimetric analysis. The presence of nitrogen- and sulfur-containing functional groups on both sides of the nanocomposite sheets facilitates the formation of strong complexes between target (i.e. noble metal ions) and the surface of the sorbent. Following elution with thiourea-HCl, the ions were quantified by FAAS. Under optimized conditions, the lower limits of detection range from 0.1 to 1.0 mu g L-1. The maximum sorption capacities are 49, 50, 45, and 50 mg g(-1) for Ag(I), Au(III), Pd(II) and Pt(II), respectively. The method was successfully applied to the extraction and determination of the analytes in wastewater (electroplating, radiological and photographical wastewater), sea water, and road dust.