Thesis (M.Sc.)--Chulalongkorn University, 2011

Polyethyleneimine-coated carbon nanotubes modified with methyl thioglycolate (CNTs-PEI-MTG) were prepared and used as adsorbent for Au(III) extraction. Carbon nanotubes (CNTs) were coated with polyethyleneimine (PEI), via physical adsorption. The PEI molecules were attached together using glutaraldehyde as crosslinking agent and subsequently modified with methyl thioglycolate (MTG) to improve the adsorption selectivity toward gold ions. The obtained products were characterized by scanning electron microscope equipped with energy dispersive X-ray analyzer (SEM-EDX), Fourier transforms infrared spectrometer (FTIR), Raman spectrometer (FT-Raman), thermal gravimetric analyzer (TGA), and ninhydrin test. The optimum amounts of PEI and MTG for CNTs coating were 2.00×10-4 and 17.86 mmol/g CNTs, respectively. The effect of certain parameters on Au(III) adsorption by the adsorbents was evaluated. Adsorption equilibrium was reached in 10 minutes. The solution pH in the range of 1.5-7 did not have any effect on the adsorption efficiency. The adsorption behavior followed Langmuir isotherm with the calculated maximum adsorption capacity of 203.7 mg Au/g. The desorption of Au(III) ions from the used adsorbent was achieved using 0.5 M thiourea in 2%(v/v) HCl solution.