Electrosorption of Toxic Heavy Metal Ions by Mono S- or N-Doped and S, N-Codoped 3D Graphene Aerogels

Abstract

S-doped three-dimensional (3D) graphene aerogels (S-3DGA) were fabricated using dithiothreitol as the sulfur source and reductant, and the obtained S-3DGA were used for the electrosorption of toxic heavy metal ions including Cu2+, Cd2+, Hg2+ and Pb2+, showing excellent removal efficiency and recyclable electrosorption. Also, S,N-codoped 3DGA (S,N-3DGA) using L-cysteine as the sources of sulfur and nitrogen as well as mono N-doped 3DGA (N-3DGA) using urea as the nitrogen source were fabricated and applied for the electrosorption of these heavy toxic metal ions. According to the concept of Hard-Soft-Acid-Base (HSAB), S-3DGA exhibit the best electrosorption performances among the three 3D graphene aerogels (3DGA) since compared with N atom, S of higher softness is favorable to the interactions with soft metal ions. Among the four tested heavy metal ions, Cu2+ of the smallest radius shows the highest removal efficiency due to the strongest electrostatic attractions.