Spray pyrolysis synthesis of mesoporous γ-AlOOH and γ-Al₂O₃ microspheres and their properties for Cr (VI) adsorption

In this work, mesoporous spherical γ-AlOOH and γ-Al2O3 particles were rapidly prepared by spray pyrolysis (SP) at different temperatures (400°C–700°C) without the use of template materials. A sol-gel-derived colloidal solution boehmite was ultrasonicated to generate fine droplets, which continuously transferred into a quartz reactor heated specific temperature constant flow N2 gas. Under ultrasonication-assisted conditions, phase change from γ-alumina occurred 500°C, leading decrease in surface area hydroxyl group density products. At 400°C, produced microspheres exhibited highest values ca. ~ 510 m2/g 2.92 mmol/g, surpassing those commercial boehmite. The Cr (VI) removal experiments revealed that have good adsorption performance towards Cr6+. optimal spheres Cr(VI) capacity ca.~ 44.5 mg/g (~74%) 27 °C pH = 5.5. After five adsorption-desorption cycles, synthesised powder remained Cr6+ adsorbing 78%. Notably, fabricated SP-γ-AlOOH capable simultaneously removing textile dye solution. This study provides facile, rapid, scalable approach for producing with improved properties adsorption.