Spectrophotometrical analysis for fabrication of pH-independent nano-sized γ-alumina by dealumination of kaolin and precipitation in the presence of surfactant composites.

The challenge with γ-Al2 O3 is its pH-dependent removal efficiency and relatively low adsorption capacity in recovery of wastewaters contaminated by cationic dyes. Therefore; the objective of present investigation was to fabricate a pH-independent nano-sized alumina powder by dealumination of kaolin for uptake of dye. The dealumination of meta-kaolin was carried out by nitric acid solution and the amorphous aluminum hydroxide was precipitated with ammonia in the presence of combined surfactants containing cetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG) and polyoxyethylene octyl phenyl ether (TX100). The nano-sized gamma alumina particles were fabricated after calcination at 800 °C and then were analyzed based on spectrophotometrical method. The rod-like nano-particles with average width of 5 nm and length of 20 nm were synthesized by precipitation in the presence of admixed surfactant, CTAB-TX100, which improves the removal efficiency due to efficient modification in the interaction of particles. TX100 also showed a significant affinity for increasing the specific surface area because of ability to prevent the particle aggregation which provides a potential for synthesis of alumina adsorbent without foaming, normally observed in the presence of CTAB. Both of mentioned powders indicated relatively pH-independent removal efficiency with higher adsorption capacity. Moreover, adsorption isotherm parameters were determined to verify the improvement of removal efficiency. The presented fabrication technique eventually overcame the pH-dependent recovery problem which is feasible for the development of adsorbents because the starting material is abundant, very low energy is needed, no hazardous waste is generated and applicable in the acidic environments.