Removal of Congo red dyes from aqueous solutions by porous γ-alumina nanoshells

Porous alumina has been shown to be an excellent adsorbent for Congo Red (CR) dye. In this work, highly porous g-Al2O3 nanoshells were synthesized from alumina coated carbon black (CB) obtained from a new deposition technique and used for removal of CR dye from aqueous solutions. Adsorption experiments were conducted in a batch mode and a series of parameters were investigated, including contact time, initial dye concentrations, ionic strength and pH of the solutions. It was found that equilibrium for CR adsorption can be reached within 30 min, much faster than reported by other studies in the literature on similar adsorbents. It was also found that the adsorption capacity of Al2O3 nanoshells is 44.8 % higher than that of alumina/CB. 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 Al2O3 nanoshells have a maximum adsorption capacity of 370.4 mg g(-1) (25 degrees C; pH 7; no salt added), better than or comparable to those reported in the literature. A pseudo-second-order kinetics model can best fit the kinetics of CR adsorption, which follows the Langmuir isotherm. The high adsorption capacity is attributed to the strong hydrogen-bonding interactions between the anionic dye and Al2O3 nanoshells surface as well as to the electrostatic interactions between CR dye and the Al2O3 nanoshells.

Automated summary

The highly porous g-Al2O3 nanoshells synthesized from alumina coated carbon black demonstrated excellent adsorption capacity for the removal of Congo Red dye from aqueous solutions. The adsorption equilibrium could be reached within 30 minutes, with a high removal efficiency of 98.6% achieved at pH 4.0. The adsorption capacity of the Al2O3 nanoshells was significantly higher than that of alumina/CB, showing superior performance in dye removal.