The purpose of this project was to fabricate the 1-dimensional nanocomposite materials with high aspect ratios and specific surface areas for the coupled degradation of refractory organic compounds and heavy metals. The 1-dimensional nanomaterials were composed of various ratios of carbon nanotubes (CNT) and titanate nanotubes (TNT) (CNT/TNT) ranging from 2.5 and 20 wt %, and alkaline hydrothermal method was used to fabricate TNT under different hydrothermal conditions. Three different TiO2 raw materials, Degussa P-25, ST-01 and sol-gel-derived TiO2 particles, serving as the starting materials, were added in 3-10 M NaOH solution at hydrothermal temperature of 60-230 C for 1-3 d using pressure bomb system. The morphology changed from nanoparticles/nanosheets, nanotubes, nanowires and then to nanoribbon as the hydrothermal temperatures increased from 60 to 230 C. ST-01 has a relatively high reactivity than those of P-25 and sol-gel-derived TiO2 nanoparticles to form high specific surface area (> 350 m2/g) nanostructured materials at 120 C for 72 h in 10 M NaOH solutions. Post heat treatment at 300 C for 4 h would produce anatase phase of TiO2, and subsequently enhanced the photoactivity of TNT. In addition, the combination of CNT with TNT at 2.5-20 wt% would increase the carboxylic and carbonyl functional groups on surfaces, resulting in the change in surface acidity and hydrophobilicity of composite nanomaterials. The composite CNT/TNT nanomaterials have a good capability toward heavy metal adsorption and the adsorption followed the order Pb2+ > Cu2+ ~ Cd2+ > As5+. The Langmurian maximum adsorption capabilities of nanomaterials were in the range 83-204 mg/g for Cu2+ and 192-588 mg/g for Pb2+, which is superior to that of CNT. The CNT/TNT ratios at 7.5 and 20 wt% have high ability towards heavy metal adsorption, presumably due to the higher amounts of carboxylic and carbonyl functional groups on surfaces. In addition, the adsorption ability of azo dye and estrone using post-heat-treated TNT or acidified CNT is better than those of composite CNT/TNT materials. Good photodegradation efficiencies of MX5B and estrone by TNT were observed, and the pseudo-first-order rate constants for MX5B and estrone photodegradation using TNT were 0.088 and 0.0818 min-1, respective, which are better than those of P-25 and ST-01 TiO2. The aquatic chemistry has a great effect on the coupled removal of pollutants as well as the stability of nanomaterials in solution. The adsorption of MX5B using 7.5 wt% CNT/TNT was inhibited by the addition of Pb2+. In the presence of Cu2+, however, the adsorbed amount of MX5B increased, presumably mainly due to the formation of complex between azo dye and Cu ion. In addition, the photocatalytic ability of TNT towards MX5B also enhanced when solution contained 2-10 mg/L Cu2+. Addition of humic acid stabilized the nanomaterials in solution, while decreased the adsorption and photodegradation efficiency of pollutants. The zeta potentials and hydrodynamic radii of nanomaterials changed significantly when the solution pH is close to the isoelectric points of nanomaterials. Results obtained in the study showed that the developed 1-D CNT/TNT nanomaterials have high specific surface areas and functional groups on surfaces, which can be adsorption heavy metals as well as organic pollutants under suitable conditions, and the adsorbed pollutants will be removed under illumination of UV-Vis light at a time.

Functionalized 1-dimensional nanomaterials, titanate nanotubes (TNT), carbon nanotubes (CNT), refractory organics, heavy metals, coupled removal