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(396b) Removal of Congo Red Dyes from Aqueous Solutions By Porous ?-Al2O3 Nanoshells

Al-Salihi, S. - Presenter, University of Missouri
Jasim, A. M., University of Missouri
Fidalgo, M. M., University of Missouri
Xing, Y., University of Missouri
Alumina coating on carbon black (alumina/CB) was prepared by a condensed layer deposition (CLD) coating process to enable nanoscale structure with high surface areas. Al2O3 nanoshells were derived after burning the alumina/CB under oxygen gas at 500 ⁰C, with a high specific surface area. Both Al2O3 nanoshells and alumina/CB were used as adsorbents to remove Congo Red dye from aqueous solutions in batch adsorption processes. The adsorbents were characterized using various techniques, such as N2 adsorption-desorption isotherms (BET), X-ray diffraction (XRD), thermo-gravimetric analysis and differential thermal analysis (TGA - DTA), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and zeta potential. Characterization results indicated that the alumina/CB and Al2O3 nanoshells yield high surface area of 290 and 217 m2/g, respectively. While wide angle XRD and FTIR studies confirmed the phase transformation of γ- Al2O3 after the removal of CB at 500 ⁰C. A series of parameters were investigated in adsorption experiments, including contact time, initial dye concentrations, ionic strength and pH of the solutions. It was found that equilibrium for Congo red adsorption can be reached within 30 min, much faster than reported by other studies in the literature on similar adsorbents. The adsorption mechanism for both samples followed the Langmuir isotherm with a pseudo second order reaction. The adsorption isotherm studies showed that Al2O3 nanoshells achieved a 44.8 % higher adsorption capacity than that of alumina/CB. The Al2O3 nanoshells have a maximum adsorption capacity of 370.4 mg/g(25 ⁰C; pH 7; no salt added), better than or comparable to those previously reported adsorbents. The adsorption capacity of Al2O3 nanoshells was more favorable at lower pH, and the optimal adsorption ability was achieved at pH 4.0 with a removal efficiency at 98.6%. The adsorption process was associated with the H-bonding and electrostatic attraction between the Congo red dye and Al2O3 nanoshells surface. Overall, these results suggest that the low cost Al2O3 nanoshells is a very efficient adsorbent for anionic Congo red dye removal from contaminated water due to their fast kinetics along with high adsorption capacity.