Ammonia Borane Promoted Synthesis of Graphene Aerogels as High Efficient Dye Adsorbent.

Graphene aerogels (GA) hold great promise as a practical adsorbent to remove contaminants from water thanks to their high specific surface area and stable chemical properties. In this work, we demonstrated a strategy by introducing ferrous ions-ammonia borane as a synergistic reducing agent for hydrothermal reduction of graphene oxide to synthesize high-performance graphene aerogel adsorbents. Reducing agent system features four aspects: (1) Ferrous ions themselves as reducing agent, (2) Ferrous ions as catalyst for ammonia borane decomposition to release hydrogen, (3) Released hydrogen as a secondary reducing agent, (4) Involved hydrogen gas bubbles facilitating the formation of pores in GA. As-synthesized GAs exhibited larger specific surface area and smaller pore diameter than only using ferrous ions as reducing agent, which benefit a lot to the adsorption and water cleaning. Adsorption experiments showed that as-synthesized GAs was high efficient in the adsorption of both cationic dye (Rhodamine B) and anionic dye (Orange G) with adsorption capacity as high as 103.6 mg·g-1 and 87.4 mg ·g-1, respectively, which is comparable to the most of state-of-the-art sorbents. The adsorption rate was greatly improved. Besides, the great adsorption performance was not limited to a certain kind of dye which is different from that of most dye adsorbents. Furthermore, kinetic investigations showed the adsorption followed a pseudo-second-order kinetics model, indicating a chemical adsorption. The adsorption isothermal studies revealed that the adsorption process was more likely took place in a monolayer manner. Thanks to the facile synthesis and excellent adsorption performance, the as-prepared GAs can be potentially applied to the practical water treatment.