Synthesis of high growth rate SWCNTs and their magnetite cobalt sulfide nanohybrid as super-adsorbent for mercury removal

Water assisted synthesis of high quality and high yield single walled carbon nanotubes (SWCNTs) was performed over Co-Mo/MgO catalyst by chemical vapor deposition (CVD) method. The effect of varying the water amount on the yield and quality of SWCNTs was studied. The as-synthesized SWCMTs were employed for mercury adsorption from aqueous solution. Also, in order to improve the adsorption process, the two magnetite SWCNTs (MSWCNTs) and magnetite SWCNTs-CoS (MSWCNTs-CoS) nanohybrids were prepared. The XRD, TGA, FE-SEM, TEM, Raman, VSM and EDX analysis were carried out to study the effects of water vapor on quality, growth rate and yield of SWCNTs as well as to verify the nanohybrids structures. It was found that with increasing the water/methane up to 8% volume ratio, the quality and yield of nanotubes were reached to their maximum levels. However, more increasing the water vapor up to 20% caused dramatic decreases in the yield and quality. Mercury adsorption properties of SWCNTs, MSWCNTs and MSWCNTs-CoS were studied with the aid of response surface methodology (RSM). Kinetic, isotherm and thermodynamic studies revealed that MSWCNTs-CoS had a very high efficiency for mercury adsorption with a very much low equilibrium time (7 min) indicating its super-adsorbent property. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.