Mechanochemical method was applied for the synthesis of γ-alumina with incorporated metal oxide (MO) species (M=Fe, Bi, Cu, Zn, and Ni). Various metal percentages (5,10, 20) were used to tune the composition of the resulting hybrid materials obtained from boehmite as alumina precursors and suitable metal salts. The required amount of boehmite and the respective metal salts were milled for 3 hours at 500rpm to obtain the desired composite. Additionally, different milling time was used to find the best procedure to obtain porous alumina with metal oxides. Block copolymer Pluronic P123 was used as a pore generating agent. The synthesized samples were calcined at 600 °C for 4 hours with a heating rate of 1°C/min. Commercial γ−Alumina (SBET = 96 m2/g), and the sample after two hours of initial grinding (SBET = 266 m2/g) were used as references. Another sample of γ Alumina after 3 hours of one-pot milling showed a higher surface area (SBET = 320 m2/g), which did not increase with further increases in milling time. So, three hours of grinding time were optimal for this material. The synthesized samples were characterized by TGA/DTG, XRF, N2 adsorption techniques. With the increase in dopant concentration the intensity of XRF peaks increases. This showed the effective incorporation of different metal oxides in the alumina framework. Similarly, the synthesized sample with the lowest metal content (5%) was tested for selective catalytic reduction (SCR). In the case of all tested samples besides pristine Al2O3 and Gallium modified samples, the increase in reaction temperature, accelerates the NOx conversion. The highest NOx conversion rate was observed for Fe modified sample reached 70% at 450 °C and for the Cu modified sample reaches 71 % at 300 °C but, started decreasing after 300 °C. Additionally, the by-product concentration (N2O) was constantly measured. For all metal oxide modified samples N2O production did not exceed 20 ppm, however, the control pristine alumina showed the highest N2O production, indicating the efficiency of MO doped samples reduces N2O production. Furthermore, the synthesized samples were tested for antimicrobial properties and found that they are active against gram-negative bacteria (P. Aeruginosa). The measured MIC (minimum inhibitory concentration) values for 10% of (Fe, Bi, Cu,) are 4 µg/mL for Zn and Ni are 8 µg/mL, whereas only alumina alone also shows 8 µg/mL.

Mechanochemical synthesis of γ−alumina with incorporated metal oxide species

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