Study of the Effectiveness of Alumina and HDTMA/Alumina Composite in the Removal of Para-Nitrophenol and the Deactivation of Bacterial Effect of Listeria monocytogenes and Salmonella spp.

Removal of para-nitrophenol (p-NP) from an aqueous solution was studied under various batch adsorption experiments, using alumina (Al(2)O(3)) and its composite hexadecyltrimethylammonium bromide (HDTMA(+)-Br(−)) as adsorbents. These were later characterized, before and after adsorption of p-NP, by thermal analysis (DSC-TG), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV/Visible spectroscopies. The results show that HDTMA(+)/Al(2)O(3) adsorbents have a greater affinity toward p-NP than Al(2)O(3) alone. Linear and non-linear forms of kinetics and isotherms were used to analyze the experimental data obtained at different concentrations and temperatures. The results indicate that the pseudo-second order kinetic model provided the best fit to the experimental data for the adsorption of p-NP on both adsorbents, and that the intra-particle diffusion was not only the rate controlling step. Both the Langmuir and Redlich-Peterson (R-P) models were found to fit the sorption isotherm data well, but the Langmuir model was better. Physical adsorption of p-NP onto the adsorbents proved to be an endothermic and spontaneous process at high temperatures, which mainly involves a hydrogen bonding mechanism of interactions between p-NP and functional groups of adsorbents. The antibacterial activity of Al(2)O(3,) HDTMA(+)-Br(−) and HDTMA(+)/Al(2)O(3) were evaluated against Listeria monocytogenes and Salmonella spp. strains using both disc diffusion and broth microdilution methods. The HDTMA(+)-Br(−) and HDTMA(+)/Al(2)O(3) displayed a bacteriostatic effect against all tested strains of Listeria monocytogenes and Salmonella spp., while Al(2)O(3) exhibited no bacterial effect against all bacterial strains tested.