Adsorption removal of Co(II) from waste-water using graphene oxide

- Preparation of porus graphene oxide (GO) by modified Hummer's method
- Well characterized and identified formation of GO by spectroscopic techniques
- Studied sorption characteristics of GO towards removal of Co(II) from water
- Well explained the adsorption mechanism of Co(II) onto GO
- Adsorption of Co(II) onto GO was complexed with rate limiting kinetics.

Graphene oxide (GO), having unique physicochemical properties, is widely used in various applications. GO prepared by a modified Hummer's method was characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and BET surface area analysis. The adsorption properties of the prepared GO towards Co(II) was elucidated by the batch adsorption method, indicating the maximum adsorption of Co(II) in a broad pH range of 5.0 to 8.0. The batch adsorption kinetics results suggest that the adsorption could be described as a rate-limiting pseudo-second-order process. To the adsorption equilibrium data applied the Langmuir, Freundlich and Temkin adsorption isotherm models for an evaluation of adsorption capacity and relevant mechanism. These results revealed that the adsorption was occurring through physical and chemical interactions between Co(II) and oxygen-containing surface functional groups, -C-O and -CO, and the π-π bonds electrons (-CC-, -CO) of GO. XPS (binding energy and shape of O1s and C1s) analysis of the GO material confirmed loading with Co(II). The maximum adsorption capacity was 21.28 mg/g of Co(II) at pH 5.5 and 298 K with 1.0 g/L GO, comparable to the reported adsorbents. Moreover, GO was precipitated upon loading with metal ions. Finally, the obtained results demonstrated the potential of the GO solid adsorbent for pre-concentration of trace heavy metals from waste effluents.