L-Lysine-grafted graphene oxide as an effective adsorbent for the removal of methylene blue and metal ions

In this paper, novel L-lysine-modified graphene oxide (Lys-GO) was synthesized through amidation. The morphological and structural properties of Lys-GO were characterized using infrared spectrometry, scanning electronic microscopy and X-ray photoelectron spectroscopy. The as-prepared Lys-GO material was systematically investigated in a series of batch adsorption experiments for the removal of methylene blue (MB) and copper ions (Cu(2+)) from wastewater. These results showed that Lys-GO is a bifunctional adsorbent for the removal of dyes and metal ions, and excellent adsorption efficiency was obtained. The maximum adsorption capacities for MB dye and Cu(2+) were 1679.1 mg/g and 186.9 mg/g at 35 °C, respectively. The kinetics of adsorption followed well the linear pseudo-second-kinetic model. The isotherm results indicated that MB adsorption can be described with the Langmuir isotherm model, while the adsorption of Cu(2+) can be described with the Freundlich model. The excellent adsorption capacity indicated that the Lys-GO may be a promising adsorption material for the removal of environmental pollutants.