The carbon gel and carbon gel doped with 0.5, 1 and 2 wt% of graphite intercalation compound were used for the removal of heavy metals from aqueous solutions. These materials were prepared by a sol-gel process that involves a polycondensation of resorcinol and formaldehyde. Nitrogen adsorption, scanning electron microscopy, energy dispersive spectroscopy and fourier transform infrared spectroscopy were used for a morpho-structural adsorbent investigation. In the present paper, Cu, Co, Pb and Ni ions adsorption experiments were carried out in batch conditions under magnetic stirring. The effect of some parameters such as contact time, metal ions’ concentration and pH were examined. Adsorption data on all sorbents, followed both the Frendlich and Langmuir models. The data better fitted the Langmuir isotherm than the Frendlich one. The highest degree of removal was achieved for Pb ions at the initial concentration of 10 mg/l and for 2 g/l adsorbent dose. Adsorption results expressed as adsorption capacities showed that carbon gel doped with 2 wt% of graphite intercalation compound is the best adsorbent. Graphical Abstract

In this study we report a one-step procedure for the fabrication of Pd–Ag bimetallic nanoparticles on the surface of a graphene oxide (rGO) support. A controlled reduction of Pd²⁺ and Ag⁺ ions on an rGO support was achieved by using a methyl ammonium borane reducing agent. The fabricated Pd–Ag/rGO bimetallic nanocomposites were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FT-IR). A Pd–Ag/rGO based electrochemical sensor was fabricated by immobilizing the as-prepared Pd–Ag/rGO bimetallic nanocomposites on to a bare glassy carbon electrode (GCE). The resulting Pd–Ag/rGO/GCE electrochemical sensor was proved to be ultrasensitive and selective towards the detection of acetaminophen (APAP) in the presence of etilefrine (ET). The linear dynamic range (LDR) for the detection of APAP was found to be 1.2–30 nM with a good limit of detection (LOD) and the limit of quantification (LOQ) of 3.26 nM and 13 nM, respectively. The newly prepared Pd–Ag/rGO/GCE-modified electrode makes a good analytical tool for the accurate determination of APAP either in its pristine conditions or in the presence of both real human samples and pharmaceutical formulations. The convenient fabrication protocol shown here can be extendable to other types of bimetallic configurations for various electrochemical sensing applications.

The present report demonstrates the development of a Pt–Ni/rGO composite electrochemical sensor for the detection of dopamine.