Influence of ɣ and ultrasonic irradiations on the physicochemical properties of CeO 2 -Fe 2 O 3 -Al 2 O 3 for textile dyes removal applications

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 °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.

Synthesis of γ-alumina (Al2O3) nanoparticles and their potential for use as an adsorbent in the removal of methylene blue dye from industrial wastewater

Non-toxic nanomaterials have gained significant importance recently in the treatment of industrial wastewater that sometimes contains organic dyes such as methylene blue. We report here an easy approach for the synthesis of γ-alumina (Al₂O₃) nanoparticles via a method that incorporates the use of formamide and the non-ionic surfactant Tween-80. Together, formamide and Tween-80 serve as an effective precipitating agent and a convenient synthetic template, respectively, in directing the growth of the alumina nanoparticles. The morphology and structure of the nanoparticles were investigated by FT-IR, XRD, TGA, SEM, EDX, elemental mapping and TEM methods. The sizes of the nanoparticles are in the 30-50 nm range. The maximum pore size is 4.13 nm and the surface area is 112.9 m² g^-1 as determined by the Brunauer-Emmett-Teller (BET) method. The nanomaterials are excellent adsorbents for the cationic methylene blue dye from aqueous solution. The effects of pH, time, temperature and concentration on the adsorption have been examined and the adsorption capacity increased from 490 to 2210 mg g^-1 as the initial concentration was increased from 50 to 400 mg L^-1 under the following conditions: pH 9, 10 min reaction time, and 60 °C. The adsorption mechanism is considered to encompass electrostatic interactions in water between the Al₂O₃ nanoparticles and the cationic methylene blue dye. These readily made nanoparticles may well prove useful in both wastewater treatment and industrial catalysis.