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 (Al2O3) 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+/Al2O3 adsorbents have a greater affinity toward p-NP than Al2O3 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 Al2O3, HDTMA+-Br- and HDTMA+/Al2O3 were evaluated against Listeria monocytogenes and Salmonella spp. strains using both disc diffusion and broth microdilution methods. The HDTMA+-Br- and HDTMA+/Al2O3 displayed a bacteriostatic effect against all tested strains of Listeria monocytogenes and Salmonella spp., while Al2O3 exhibited no bacterial effect against all bacterial strains tested.

Characterization of Ziziphus lotus' Activated Carbon and Evaluation of Its Adsorption Potential.

This study aims to prepare activated carbon from an interesting biomaterial, corresponding to the cores of Ziziphus lotus, for the first time to the best of our knowledge, according to a manufacturing process based on its chemical and thermal activation. These cores were chemically activated by sulfuric acid for 24 h and then carbonized at 500°C for 2 hours. The obtained activated carbon was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller (BET) analysis. The adsorption of methylene blue (MB) on the activated carbon was evaluated, by Langmuir and Freundlich models examination, in order to explain the adsorption efficiency in a systematic and scientific way. Moreover, pseudo-first-order and pseudo-second-order kinetic models were used to identify the mechanisms of this adsorption process. The characterization results showed an important porosity (pore sizes ranging from 10 to 45 µm), a surface structure having acid groups and carboxylic functions, and a specific surface of 749.6 m2/g. Results of the MB adsorption showed that this process is very fast as more than 80% of MB is adsorbed during the first 20 minutes. In addition, increasing the contact time and temperature improves the MB removal process efficiency. Moreover, this adsorption's kinetic modeling follows the pseudo-second-order model. Furthermore, data on the adsorption isotherm showed a maximum adsorption capacity of 14.493 mg/g and fit better with the Langmuir model. The thermodynamic parameters (∆G0, ∆S0, and ∆H0) indicate that the adsorption process is endothermic and spontaneous. Therefore, Ziziphus lotus can be used as a low-cost available material to prepare a high-quality activated carbon having a promising potential in the wastewater treatment.

Interfacial electrochemical properties of natural Moroccan Ghassoul (stevensite) clay in aqueous suspension.

A raw Moroccan clay locally named "Ghassoul" (Gh) was characterized using several techniques such as Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Brunauer, Emmett and Teller method (BET), Scanning Electron Microscopy (SEM) and simultaneous Thermo-Gravimetric and Differential Thermal Analysis (TGA/DTA). These techniques indicate that the Gh consists essentially of steveniste, calcite, dolomite and quartz. The study of the interfacial electrochemical properties of Gh in different solutions of electrolyte salts (NaCl, CsCl, NaF, NaBr and LiCl) was carried out using the potentiometric and conductometric titrations It was shown that the Gh particles were stable in aqueous phase within the pH range (3-12) and the point of zero charge (PZC) was located at pH = 10.7. The adsorption sequence, carried out at various ionic strengths, showed that the adsorption mechanism onto the Gh particles is both electrostatic and specific at pH below the pHpzc, while at a pH range greater than the pHpzc the mechanism is electrostatic in nature. The total number of surface sites, determined using the graphical extrapolation method, was 11OH/nm2. Ionization constants ( p K int + and p K int - ) in the presence of various electrolytes have also been determined and their values are 10.08 and 12.38, respectively.

Performances of local chitosan and its nanocomposite 5%Bentonite/Chitosan in the removal of chromium ions (Cr(VI)) from wastewater.

The present work focuses on the study of the application of abundant and less expensive materials such as chitosan (CS) and bentonite/chitosan nanobiocomposite (nano 5%Bt/CS) in the removal of hexavalent chromium. The adsorption behavior of the prepared materials (CS and nano 5%Bt/CS) was tested for the removal of chromium (VI) ions in a synthetic solution and wastewater from a tanning industry. Spectroscopic analysis like techniques FTIR, XRD and SEM/EDX have been used to characterise the adsorbents before and after their contact with chromium ions. The experimental data indicate that the adsorption of chromium proceeds kinetically according to a pseudo-second order model on both adsorbents and the apparent activation energy (Ea) have been measured to be 4.11kJmol-1 and 15.98kJmol-1 for chitosan and nano 5%Bt/CS, respectively. It was found that the non-linear modelling of experimental isotherms was well adapted to the Langmuir and Redlich-Peterson models. Thermodynamic parameters (i.e., change in the free energy (ΔG°), the enthalpy (ΔH°), and the entropy (ΔS°)) have been also, evaluated and the results revealed that the removal of chromium ions on both solids was done via physical adsorption. The adsorption test on a real rejection of the tanning industry shows that the CS and nano 5%Bt/CS can substitute other more expensive adsorbents.

Adsorption studies of Cu(II) onto biopolymer chitosan and its nanocomposite 5%bentonite/chitosan.

Chitosan (CS) and nanocomposite 5%bentonite/chitosan (5%Bt/CS) prepared from the natural biopolymer CS were tested to remove Cu(II) ions using a batch adsorption experiment at various temperatures (25, 35 and 45°C). X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis/differential thermal analysis (TGA/DTA) were used in CS and the nanocomposite characterisation. This confirmed the exfoliation of bentonite (Bt) to form the nanocomposite. The adsorption kinetics of copper on both solids was found to follow a pseudo-second-order law at each studied temperature. The Cu(II) adsorption capacity increased as the temperature increased from 25 to 45°C for nanocomposite adsorbent but slightly increased for CS. The data were confronted to the nonlinear Langmuir, Freundlich and Redlich-Peterson models. It was found that the experimental data fitted very well the Langmuir isotherm over the whole temperature and concentration ranges. The maximum monolayer adsorption capacity for the Cu(II) was 404-422 mg/g for CS and 282-337 mg/g for 5%Bt/CS at 25-45°C. The thermodynamic study showed that the adsorption process was spontaneous and endothermic. The complexation of Cu(II) with NH(2) and C = O groups as active sites was found to be the main mechanism in the adsorption processes.