Highly ordered macroporous γ-alumina prepared by a modified sol-gel method with a PMMA microsphere template for enhanced Pb2+, Ni2+ and Cd2+ removal

The adsorption performance of three-dimensionally ordered macroporous (3DOM) γ-alumina was investigated for enhanced Pb2+, Ni2+ and Cd2+ removal. The synthesis was based on a modified sol-gel method using a colloidal crystal template (CCT) method based on PMMA microspheres. The structure was characterized by means of FTIR spectroscopy and XRD analysis. The three-dimensional structure was examined by scanning electron microscopy, which enabled image analysis that showed significantly low shrinkage (8.77%) after calcination at 800 °C. The influential parameters, including contact time and adsorbent dosage, were investigated in a batch adsorption study. The adsorption equilibrium and kinetic data were found to be in agreement with the Freundlich isotherm for Pb2+ removal and the Dubinin-Radushkevich isotherm for Ni2+ and Cd2+ removal. The time-dependent adsorption was best described by a pseudo-second-order kinetic model and the Weber-Morris model. High adsorption capacities: 95.39, 23.32 and 25.39 mg/g were obtained for Pb2+, Cd2+ and Ni2+ removal at 45 °C, respectively. The existence of interconnected macroporous and mesoporous structures of highly ordered γ-alumina enabled a higher adsorption capacity in comparison with literature data for others alumina-based adsorbents.