Microfluidic generation of 3D graphene microspheres for high-efficiency adsorption

The three-dimensional graphene microspheres with well-defined shape and size were prepared successfully by a novel approach, i.e., a combination of microfluidic device and freeze-drying. In the synthetic process, a pragmatic and facile device has been designed for the controllable generation of uniform-sized droplets. Followed by freeze-drying, highly porous spherical graphene microballs were obtained for further research. It is worth noting that the size of the droplets can also be controlled by adjusting the flow rate ratio of each phase. Afterward, the morphology, structure and character of the three-dimensional graphene particles are characterized by scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Due to their highly porous structure, the as-prepared 3D graphene microspheres were employed as adsorbent. The adsorption capacity of acid orange 7 and Pb(II) was about 71.9 and 147.7 mg g−1, respectively. The results showed that the porous 3D graphene microspheres as adsorbent possessed excellent adsorption ability for organic and inorganic contaminants in this work, showing their potential applications in environmental pollutant treatment.