Recycling supercapacitor activated carbons for adsorption of silver (I) and chromium (VI) ions from aqueous solutions

In this study, we reported on the recycling of carbon materials from spent commercial supercapacitors and its application as low-cost adsorbent for high-efficiency removal of Ag(I) and Cr(VI) ions from aqueous solutions. Adsorption kinetics and isotherms, and effects of initial pH were carried out to investigate the adsorption performance of the recycled supercapacitor activated carbon (RSAC), whereas a series of characterizations such as SEM, EDX, BET, XPS, XRD and FTIR were employed to detailedly analyse the adsorption mechanism. The RSAC showed maximal adsorption capacity for Ag(I) and Cr(VI) of 104.0 and 96.3 mg g⁻¹, respectively, with adsorbent dosage of 2 g L⁻¹ and initial ions concentration of ∼2000 mg L⁻¹ at room temperature (23 ± 1 °C), and the adsorption was rapid and influenced by the initial pH value. The outstanding adsorption performance of RSAC was attributed to the high specific surface area (1403 m² g⁻¹) and abundant multifarious oxygenic groups which could participate in the electrostatic attraction and reduction reaction of Ag(I) and Cr(VI) during the adsorption process. Furthermore, the predominate species of the adsorbed toxic Ag(I) and Cr(VI) on the surface of RSAC was metallic silver particle (about 2 μm) and harmless Cr(III), respectively, thus it was possible for further recycling and disposal.