Solid state synthesis of MgAl2O4 nanomaterials and solar light-induced photocatalytic removal of Malachite Green

Spinel MgAl2O4  nanopowders were synthesized by one-step solid state reactions using Al(NO3)3.9H2O and MgSO4 raw materials at stoichiometric 1 : 2, Mg : Al molar ratio at a constant reaction temperature of 1000 ºC for 8 h (S1), 10 h (S2) and  24 h (S3). 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 MgAl2O4 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 MgAl2O4 powders possessed strong light absorption properties in the ultraviolet-visible region. Direct optical band gap energies were calculated as 3.4, 2.9 and 3.1 eV for S1, S2 and S3, 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 (0.2 mL H2O2, 25 mg catalyst and 40 min catalytic reaction time for the removal of 80 mL of 100 ppm MG solution) were modeled and achieved by the design expert software for S1. The degradation yield in the condition was 100 % for S1.