Fabrication of uniform porous CNTs/activated carbon composite spheres by oil-drop method in stratified oils and their adsorption of VB12

Abstract

Presented is a flexible route to prepare uniform porous carbon nanotubes/activated carbon (CNTs/AC) composite spheres with high adsorption capacity. In this work, CNTs were firstly dispersed in ethanol aqueous solution of phenolic formaldehyde (PF) resin and then the transitional CNTs/PF composite spheres were synthesized by an oil-drop method. Meanwhile the CNT suspension drops were gradually cured in stratified oils with different densities. Subsequently, after being carbonized at 600 °C, steam activated at 800 °C and followed by alkali and deionized water wash, the resultant porous CNTs/AC composite spheres were acquired with CNTs of more than 65 wt%. Remarkably, the adsorption of VB₁₂ by the CNTs/AC composite spheres was as high as 60.36 mg g⁻¹, which was 4.32 and 3.96 times that of activated carbon beads and macroporous resin beads, respectively. Observations and microstructure analyses indicated that the good sphericity of the CNTs/AC spheres could be attributed to the suspended state of the CNTs/PF drops during curing which was supported by the stratified oils, and that the interconnected porous structure should be developed synergistically by ethanol and water evaporation during curing, carbonization of PF resin and activation of CNTs/AC spheres.