Solid state synthesis of MgAl۲O۴ nanomaterials and solar light-induced photocatalytic removal of Malachite Green

Spinel MgAl۲O۴  nanopowders were synthesized by one-step solid state reactions using Al(NO۳)۳.۹H۲O and MgSO۴ raw materials at stoichiometric ۱ : ۲, Mg : Al molar ratio at a constant reaction temperature of ۱۰۰۰ ºC for ۸ h (S۱), ۱۰ h (S۲) and  ۲۴ h (S۳). The synthesized materials were characterized by powder X-ray diffraction (PXRD) technique. Structural analyses were performed by FullProf program making use of profile matching with constant scale factors. The results showed that the patterns had a cubic MgAl۲O۴ structure similar to the space group . Through textural analysis BJH (Barrette Joiner Halenda) and BET (Brunauer Emmett Teller) methods, the obtained materials were evaluated in terms of average pore size, specific surface area and average pore volume .The morphology of the obtained materials was studied by FESEM images. Ultraviolet–visible (UV-Vis) spectra showed that the nanostructured MgAl۲O۴ powders possessed strong light absorption properties in the ultraviolet-visible region. Direct optical band gap energies were calculated as ۳.۴, ۲.۹ and ۳.۱ eV for S۱, S۲ and S۳, respectively. The photocatalytic performance of the synthesized nanomaterials was investigated for the degradation of pollutant Malachite Green (MG) in aqueous solutions under solar light. Optimum conditions (۰.۲ mL H۲O۲, ۲۵ mg catalyst and ۴۰ min catalytic reaction time for the removal of ۸۰ mL of ۱۰۰ ppm MG solution) were modeled and achieved by the design expert software for S۱. The degradation yield in the condition was ۱۰۰ % for S۱.

Keywords:

Bandgap , Dye degradation , Magnesium aluminate spinel , Malachite green , Nano-photocatalyst