Enhanced adsorption of phenols from liquids by aluminum oxide/carbon nanotubes: Comprehensive study from synthesis to surface properties

In the present work, alumina/carbon nanotube nanocomposite was synthesized and characterized using field emission scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface analyzer. The nanocomposite was evaluated for the 4-chlorophenol and phenol removal from aqueous solution with comparison to the pristine carbon nanotubes. Batch adsorption experiments were carried out to evaluate the effect of pH, agitation speed, contact time, adsorbent dosage, and initial concentration on the 4-chlorophenol and phenol removal efficiency. Experimental result showed the adsorption of 4-chlorophenol and phenol by nanocomposite to be pH dependent with the highest removal achieved at pH 6. CNTs showed better adsorption efficiency than CNT-Al₂O₃ which could be assigned to the increase in the surface area from 155.5 m²/g of CNT to 227.5 m²/g of CNT-Al₂O₃. Langmuir and Freundlich isotherm models were applied for analyzing adsorption equilibrium data of 4-chlorophenol removal on the as-prepared nanocomposite and pristine carbon nanotubes, which suggested that the Langmuir model provides better correlation of the experimental data with R² of 0.994 and 0.999 respectively. While for phenol, correlation coefficients of Langmuir adsorption isotherm model were 95% and 99.4% for CNT and CNT-Al₂O₃ respectively.