Synthesis and characterization of hierarchical γ-AlOOH and γ-Al2O3 microspheres with high adsorption performance for organic dyes

Abstract

A segmented heating process with hexadecyl trimethyl ammonium bromide (CTAB) as a surfactant and pore forming agent has been successfully developed to synthesize hierarchical γ-AlOOH and γ-Al₂O₃ microspheres with ultra-excellent adsorption performance for Congo red (CR). The effects of raw material proportion, heating system and reaction time on the structure, morphology and crystal phase of the hierarchical structures were systematically investigated by XRD, SEM, TEM, BET, NMR and FT-IR. A possible formation mechanism of the flower-like microsphere was proposed and discussed according to the time dependent experiments. The adsorption properties, adsorption isotherms and kinetics for Congo red onto the fabricated samples were also investigated. Morphologies of the products obtained by this process were more uniform and complete. The surfactant (CTAB), removed by calcination at 700 °C, increased the surface area and porosity of the samples, and resulted in ultra-excellent adsorption properties for Congo red. The adsorption isotherms of the hierarchical γ-AlOOH and γ-Al₂O₃ microspheres both fitted the Langmuir model well with maximum adsorption capacities of 214.59 mg g⁻¹ and 416.05 mg g⁻¹, respectively, which suggested the possibility that they could be applied as a candidates for highly efficient adsorbents.