“…While for pH below 8.58 and 7.84 the surface is positively charged. The adsorption of phenol is more important in the case of surfaces with positive charges, for this we worked in pH < pH pcn [32] for the phenol adsorption onto RCG and CCG.Fig. 5pH pzc of RCG (a) and CCG(b).…”
Section: Resultsmentioning
confidence: 99%
“…This could be explained by the fact that in the basic state (pH > pH pcn ), the dominant charge of the surface of the adsorbents are negative, which decreases the adsorption of phenolates carrying the same charge. In the acidic state, the positive charges are dominant at the surface of the adsorbent and so there is a substantially high electrostatic attraction between the positive charges of the surface of the adsorbent and the negative charges of the formed phenolates which promote the adsorption [32]. Indeed, the value of pH is fixed at 4 for adsorption process giving to the fact that, for pH > 9 the phenol exists in the form of phenolates C 6 H 5 O − (pKA = 9.95) and in molecular form at acid state [49].…”
Section: Resultsmentioning
confidence: 99%
“…After fixing the initial pH i , 20 mg of the clay is added to each solution and stirred for 24 h at room temperature, and then the final pH f is measured to plot the pH f = f (pH i ) curve. The pH pzc is determined atpH f = pH i [32].…”
In this work, the phenols removal of phenol from water by raw clay (RCG) and calcined one at 1000 °C (CCG) of Goulmima city (Morocco) was investigated. The kinetics and isotherms experiments were also studied at pH = 4. The results indicated that the phenol adsorption reached equilibrium within 3 h, and the removal of phenol was enhanced at the same temperature by CCG (2.932 mg/g) adsorbent, compared to RCG (1.640 mg/g) due to the removal of organic matter by heat treatment, and an increase in adsorption temperature, indicating the endothermic process. The adsorbents were characterized by means of X-ray fluorescence, FTIR, XRD, B.E.T, and TGA/DTA analysis and showed that the clay consists essentially of silica and alumina. The experimental data were examined by using linear and nonlinear forms of the kinetics and the isotherms models. Based on the errors of the calculated values of R
2
(Coefficient of determination), χ
2
(Chi-square) and standard deviation (Δq (%)), it was found that the nonlinear forms of second-order kinetic model and Freundlich and Redlich-Peterson (R–P) isotherm models are best fit the experimental data for both adsorbents. However, the enthalpy ΔH° is less than 20 kJ/mol and the free energy ΔG° has a negative value, which shows that the adsorption is done physically and spontaneously on heterogeneous sites. The interest of this study is the use of FTIR and XRD to determine the effect of calcination on the phenol adsorption mechanism. However, the analysis of both adsorbents, before and after adsorption of phenol, shows that the adsorption mechanism of phenol is provided by the hydrogen bonding of the water molecules.
“…While for pH below 8.58 and 7.84 the surface is positively charged. The adsorption of phenol is more important in the case of surfaces with positive charges, for this we worked in pH < pH pcn [32] for the phenol adsorption onto RCG and CCG.Fig. 5pH pzc of RCG (a) and CCG(b).…”
Section: Resultsmentioning
confidence: 99%
“…This could be explained by the fact that in the basic state (pH > pH pcn ), the dominant charge of the surface of the adsorbents are negative, which decreases the adsorption of phenolates carrying the same charge. In the acidic state, the positive charges are dominant at the surface of the adsorbent and so there is a substantially high electrostatic attraction between the positive charges of the surface of the adsorbent and the negative charges of the formed phenolates which promote the adsorption [32]. Indeed, the value of pH is fixed at 4 for adsorption process giving to the fact that, for pH > 9 the phenol exists in the form of phenolates C 6 H 5 O − (pKA = 9.95) and in molecular form at acid state [49].…”
Section: Resultsmentioning
confidence: 99%
“…After fixing the initial pH i , 20 mg of the clay is added to each solution and stirred for 24 h at room temperature, and then the final pH f is measured to plot the pH f = f (pH i ) curve. The pH pzc is determined atpH f = pH i [32].…”
In this work, the phenols removal of phenol from water by raw clay (RCG) and calcined one at 1000 °C (CCG) of Goulmima city (Morocco) was investigated. The kinetics and isotherms experiments were also studied at pH = 4. The results indicated that the phenol adsorption reached equilibrium within 3 h, and the removal of phenol was enhanced at the same temperature by CCG (2.932 mg/g) adsorbent, compared to RCG (1.640 mg/g) due to the removal of organic matter by heat treatment, and an increase in adsorption temperature, indicating the endothermic process. The adsorbents were characterized by means of X-ray fluorescence, FTIR, XRD, B.E.T, and TGA/DTA analysis and showed that the clay consists essentially of silica and alumina. The experimental data were examined by using linear and nonlinear forms of the kinetics and the isotherms models. Based on the errors of the calculated values of R
2
(Coefficient of determination), χ
2
(Chi-square) and standard deviation (Δq (%)), it was found that the nonlinear forms of second-order kinetic model and Freundlich and Redlich-Peterson (R–P) isotherm models are best fit the experimental data for both adsorbents. However, the enthalpy ΔH° is less than 20 kJ/mol and the free energy ΔG° has a negative value, which shows that the adsorption is done physically and spontaneously on heterogeneous sites. The interest of this study is the use of FTIR and XRD to determine the effect of calcination on the phenol adsorption mechanism. However, the analysis of both adsorbents, before and after adsorption of phenol, shows that the adsorption mechanism of phenol is provided by the hydrogen bonding of the water molecules.
“…X-ray diffraction (XRD) patterns were recorded using an X'PERT MPD-PRO wide angle X-ray powder diffractometer provided with a diffracted beam monochromator and Ni filtered CuKɑ radiation (λ ¼ 1.5406 Å). The 2θ angle was scanned between 4 and 30 range with a counting time of 2.0 s at steps of 0.02 [16].…”
Oil mill wastewater (OMW) is the main liquid discharge from oil mills, it is considered as a dangerous pollutant due to its toxic chemical compounds which are unloaded directly in the environment without any treatment. The aims of this study were to evaluate the effectiveness of OMW adsorption on clay as a good method for the elimination of toxic chemical compounds and to study the application of treated OMW as an irrigation source in agricultural field. For this, Clay was collected from the city of Agourai (Meknes region, Morocco) and characterized by X-ray diffraction, X-ray fluorescence spectrometry, BET and FTIR analysis. Moreover, the treated OMW was analyzed using UHPLC-ESI-MS and the determination of total phenolic content (TPC) was also performed. However, the application of the treated OMW in agricultural field was performed by the determination of its effect on the germination of Lepidium sativum seeds (in vitro) and as a source of irrigation of Vicia faba plants (in situ). The results of this study showed that OMW had the following physicochemical characteristics: average pH of 4.88, TPC of 4.75 g/l, COD of 80 g/l, BOD5 of 18.72 g/l, conductivity of 16.05 cm-1, dry matter of 135.7 g/l and volatile matter of 58.7 g/l. The adsorption on clay had increased the pH from 4.88 to 6.14 and reduced significantly the organic matter (42% of COD and 57.4% of phenolic compounds). UHPLC-ESI-MS analysis showed the presence of a wide variety of organic compounds in OMW, with the appearance of new compounds after adsorption. Moreover, the use of treated OMW as a source of irrigation showed a significant effect on the germination of Lepidium sativum seeds and the growth of Vicia faba plants. From this study, we can conclude that the adsorption on clay is a good method for the treatment of OMW, which became non-toxic for environment and can be used as a source of irrigation in agricultural field.
“…The adsorption is probably the main driving force behind the apparent electrocatalysis. Literature data [32] report that the adsorption of nitrophenol on the alumina surface does not occur through electrostatic interactions via −OH 2 + groups. The adsorption proceeds through the donor/acceptor complexes, where the nitrophenol acts as the acceptor and alumina oxygen as the strong donor.…”
Nickel-alumina composites with various content of nickel were synthetized by
sol-gel method. The characterization of samples was performed by diffuse
reflectance spectroscopy and electrochemical impedance spectroscopy using
the Mott-Schottky analysis. Glassy carbon electrode modified by synthesized
composites was investigated for reduction of 4-nitrophenol. Modification of
glassy carbon electrode with composite sample led to the strong apparent
electrocatalysis. Principal component analysis was used to establish
correlation between structural, textural and electrochemical data of
investigated composites.
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