Polyethylenimine‐functionalized multiwalled carbon nanotube for the adsorption of hydrogen sulfide

ABSTRACT Functionalized multiwalled carbon nanotubes (MWCNTs) were synthesized with ethane diamine and polyethylenimine (PEI) with molecular weights of 1800 [MWCNT‐PEI weight‐average molecular weight (Mw) = 1800] and 70,000 (MWCNT‐PEI Mw = 70,000), respectively. The structures and properties of the ethane diamine functionalized MWCNTs and PEI‐functionalized MWCNTs were characterized by Raman spectroscopy, thermogravimetric analysis, X‐ray powder diffraction, and scanning electron microscopy. An increase with the D/G (D, Disorder band; G, Graphite) ratio of the functionalized MWCNTs in the Raman spectra proved that the ethane diamine and PEI were successfully bonded to the surface of the pristine MWCNTs. The results of TGA also confirmed this. In addition, the structure of the functionalized MWCNTs showed no significant changes compared with the pristine MWCNTs; this was confirmed by X‐ray powder diffraction. Hydrogen sulfide (H2S) sorption on the functionalized MWCNTs was studied by UV spectroscopy. As expected, the results of UV spectroscopy shows that the MWCNTs bonded with higher molecular weight PEI had a more excellent H2S adsorption efficiency than those bonded with low‐molecular‐weight PEI and ethane diamine, a micromolecular amine. The effects of the pH and temperature on the adsorption of H2S were also studied. Under the conditions investigated, the maximum first‐time H2S adsorption efficiency of 1.94 mmol/g was observed for MWCNT‐PEI (Mw = 70,000) in the 60 mg/L sodium hydrosulfide (NaHS) aqueous solution. In addition, the H2S reversible adsorption of the functionalized MWCNTs was conducted, and the second‐time H2S adsorption efficiency of MWCNT‐PEI (Mw = 70,000) reached 1.83 mmol/g in the 60 mg/L NaHS aqueous solution. The results demonstrate that the MWCNTs decorated with high‐molecular‐weight PEI were potentially excellent and reversible H2S adsorbents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44742.