The Modification of Carboxylated Multi-Walled Carbon Nanotube Using Titanium Dioxide for Surface Adsorption of Indigo Carmine Dye From Aqueous Environment (Thermodynamics and Kinetics Study)

In this study, the doping effect of TiO2 on carboxylated multi-walled carbon nanotube (FMWCNT) on adsorption of Indigo carmine dye, an acidic dye, form aqueous enviroment has been Investigated. TiO2 was doped on FMWCNT surface and it was checked by fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and scanning electron microscope (SEM). The dye adsorption experiments were carried out by using a batch procedure. The effects of contact time, pH, dye concentration, adsorbent dose and temperature on adsorption of indigo carmine by TiO2 doped and undoped adsorbents (FMWCNT /TiO2 and FMWCNT) were evaluated. Pseudo first order, pseudo second order and intra-particle kinetic models were used to describe adsorption kinetics. Furthermore, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms were used to describe equilibrium adsorption of the indigo carmine dye on adsorbents. The obtained data were then analyzed using linear regression method. Experimental results have shown that acidic pH (3.0), favored the adsorption for both adsorbents. The dye adsorption equilibrium was attained after 90 minute of contact time. The capacity of adsorption of indigo carmine increases with doping of TiO2 on FMWCNT. Pseudo second order kinetic model is best fitted with experimental data for both adsorbents. The equilibrium data of dye adsorption on both adsorbents are best fitted with Langmuir isotherm at 25, 35 and 45 ºC. Thermodynamic study of dye adsorption on FMWCNT and Fmwcnt /TiO2 adsorbents showed that the adsorption process is exothermic and chemisorption.