Understanding the high adsorption-reduction performance of triethanolamine modified graphene oxide for silver ions

Abstract Graphene oxide (GO) and its derivatives have attracted much attention for metal ions removal in aqueous solution. Here, the adsorption-reduction performance and mechanism of triethanolamine (TEOA) modified GO towards silver ions (Ag + ) were investigated. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) characterizations indicated that TEOA molecules were tightly anchored on GO surface through two types of interactions including chemical interaction and electrostatic interaction. The adsorption performance results showed that the electrostatic interaction TEOA on GO contributed to a high initial adsorption capacity towards Ag + , while chemical interaction TEOA on GO led to a constant rising of the adsorption capacity with increase of Ag + concentration. Theoretical calculation, XPS and transmission electron microscopy (TEM) characterization further revealed the chemical interaction TEOA produced pyridine N species which exhibited strong reducibility, so that Ag + was adsorbed and reduced to Ag metal thereon, and further aggregated into larger particles. Integrating the results of instrument characterizations, adsorption performance, and theoretical calculation, we proposed that the adsorption-reduction-aggregation-regeneration circulation led to the constant rising of adsorption capacity of Ag + on GO with chemical-bonded TEOA. The conclusions in this paper provide us a new insight into the adsorption mechanism of Ag + on TEOA modified GO and rendered an efficient alternative for the recovery and removal of metal ions in aqueous solution.