Amine Khelifa

Cu(II) adsorption by halloysites intercalated with sodium acetate

Intercalated halloysites with sodium acetate at various contact time were prepared. The resulting materials were characterised by X-ray powder diffraction, Fourier transformed infrared spectroscopy, scanning electronic microscopy, and specific surface area evaluation. The modified halloysites were employed as Cu(II) adsorbents from aqueous solutions. Various parameters were studied through the batch method. Kinetic data, equilibrium isotherms, and thermodynamic parameters were evaluated by considering several models. The fraction of halloysite intercalated with sodium acetate remained low, up to 7 days, then linearly increased with contact time. Thirty days were required to achieve a ratio of 91%. For this sample, a proliferation of small tubes (nanotubes) was evidenced. The best results were achieved with the pseudo-second-order kinetic model associated with intraparticle diffusion and with the Redlich-Peterson isotherm, for the equilibrium data. The thermodynamic data show that adsorption would be spontaneous at low temperatures, of exothermic nature, resulting in an adsorbate-adsorbent system much more ordered. The insertion of CH(3)COONa into halloysite significantly affects the Cu(II) adsorption. The magnitude in enhancement of copper adsorption on solid phase thus depends on the content of the carboxylic functional groups, which increases with the insertion of CH(3)COONa into the halloysitic matrix. The involved mechanism is quite complex. It implies electrostatic considerations and a cationic exchange process. The most intercalated sample was found to be very effective as adsorbent of copper(II) from aqueous solutions.

The Adsorption of Pentachlorophenol from Aqueous Solutions onto Exchanged Al-MCM-41 Materials

The ability of a mesoporous molecular sieve to adsorb chlorinated phenols was studied experimentally. Thus, the adsorption isotherms of pentachlorophenol (PCP) from aqueous solutions were measured on (M)Al-MCM-41 (M = Na+, K+, Cu2+, Cr3+) at intervals of 10 K between 303 K and 323 K. The experimental isotherms obtained were of the S-type in terms of the classification of Giles and co-workers. The best fit of the adsorption isotherm data was obtained using the Freundlich model. The adsorption affinity of PCP increased in the order (K)Al-MCM-41 < (Cr)Al-MCM-41 < (Na)Al-MCM-41 < (Cu)Al-MCM-41. At the same temperature, the adsorption of PCP on (Cu)Al-MCM-41 was more pronounced compared to its adsorption on alumina-pillared montmorillonite and mesoporous alumina aluminium phosphates. Analysis of the isosteric curves showed that (Cu)Al-MCM-41 and (Na)Al-MCM-41 presented a heterogeneous profile. In contrast, (K)Al-MCM-41 and (Cr)Al-MCM-41 did not exhibit energetic heterogeneity throughout the entire range of coverage.

Adsorption de CO2 par des zeolithes X echangees par des cations bivalents

Abstract Adsorption of carbon dioxide by X zeolites exchanged with bivalent cations. The adsorption of carbon dioxide by X zeolites exchanged by Mg 2+ , Sr 2+ , Zn 2+ and Cu 2+ cations was studied by thermogravimetry. The corresponding isosteric heats of adsorption decrease with the filling of pore volume, except for Cu(63)X. This evolution of the heat indicates a specific interaction between cations present within supercages and CO 2 molecules. Several models have been used in order to describe the experimental isotherms. The best fit of sorption isotherm data was obtained with the Sips model.

Improving of the adsorption capacity of halloysite nanotubes intercalated with dimethyl sulfoxide

Algerian halloysite intercalated with dimethyl sulfoxide (DMSO) was prepared. The starting (H) and resulting (H-DMSO) materials were characterized by X-ray powder diffraction, Fourier transformed infrared spectroscopy, thermal analysis, transmission electron microscopy, pore-size distribution analysis, and employed as crystal violet (CV+) adsorbents from aqueous solutions. Intercalation reaches a rate of 95% and increases the basal spacing to 11.2 Å. (CH3)2SO interacts with the inner surface hydroxyls of halloysite through new hydrogen bonds with the S=O groups. The release of DMSO occurs in two phases: a partial elimination at 195 °C and a second part due to the DMSO combustion at 277 °C. The TEM image of H-DMSO reveals halloysite nanotubes (HNTs) polydisperse in length and diameter. A heterogeneous distribution in the nanotube size was highlighted with pore diameters of 10–11, 20.6, 28.6, and 37.0 nm, in correlation with transmission electron microscopy. The Redlich–Peterson equation describes efficiently the CV+ adsorption onto the modified sample. H-DMSO adsorbs 93.6 against 50.9 mg g−1 for the starting material. This improving of the adsorption capacity of DMSO-intercalated HNTs, was explained via the behavior of the intercalated DMSO molecules. Intercalation constitutes a key procedure for developing new nanocomposites, attractive in technological applications, such as effective adsorbents.

Removal of a reactive textile azo dye by dolomitic solids: kinetic, equilibrium, thermodynamic, and FTIR studies

AbstractAlgerian dolomite was treated at different temperatures in the 600–1000°C range and characterized by XRD and SEM. The obtained samples, named dolomitic solids, were used in the removal of Reactive Black 5 (RB5) from aqueous solutions. A literature survey shows that the data about the dye adsorption by dolomites are almost non-existent. Kinetic data, equilibrium isotherms, thermodynamic parameters, pH influence, and FTIR study were considered. The kinetic mechanism is enough complex, involving different models such as those of pseudo-second-order, intraparticle diffusion, and Elovich. For all dolomitic solids, the capacity in RB5, at equilibrium, strongly increases with increasing adsorption temperature. The affinity sequence is D900 (dolomite treated at 900°C) > D800 > D1000 > D600 > raw dolomite. Knowing that D900 adsorbs 125.9 mg g−1, it appears very effective for removing reactive dyes from wastewaters. The isotherms are found to be overall well represented by the Redlich–Peterson equation. The...

Removal of catechol from water by modified dolomite: performance, spectroscopy, and mechanism

Dolomite was treated at 800 °C (D800), characterized, and used in the adsorptive removal of catechol (1,2-dihydroxybenzene) from aqueous solutions. The performances of the D800 sample, named dolomitic solid, were compared with those of the raw material. A bibliographic review shows that the data on the adsorption of phenolic compounds by dolomites are non-existent. Kinetic data, equilibrium isotherms, thermodynamic parameters, and pH influence were reported. Special attention was paid to the spectroscopic study, before and after adsorption. The purpose was to understand the mechanism of catechol uptake on dolomitic materials. Kinetics follows the pseudo-second order model. The Redlich-Peterson isotherm provides the best correlation of our isotherms. Affinity follows the sequence: D800 ≫ raw dolomite. The process is spontaneous at low temperatures and exothermic. After catechol adsorption, the shape of the band in the 3,600-3,000 cm-1 range and its red shift towards 3,429 cm-1 reflect a deep involvement of OH groups both of D800 and catechol, which confirm hydrogen bonding via their respective OH. On this basis, a schematic illustration was proposed. The understanding of the phenolic compound-dolomitic solid interactions constitutes a fundamental approach to developing the application of these materials in wastewater treatment.

Kinetics and Isotherms Adsorption of Reactive Dye by Thermally Treated Dolomite

Kinetic and equilibrium data of the adsorption of reactive black 5 (RB5) from synthetic solutions on Algerian dolomite were determined experimentally. The obtained samples, i.e., raw dolomite and its form heated at 900 °C (D900), were characterized by XRD and SEM. The kinetic mechanism is enough complex, involving different models such as those of pseudo-second order, intraparticle diffusion, and Elovich. The adsorption of RB5 at equilibrium increases strongly with increasing adsorption temperature. The affinity sequence is D900 >> raw dolomite with amounts adsorbed of 125.9 and 38.20 mg g−1, respectively. This difference would be correlated with the weight loss percentage and crystallographic properties. The kinetic mechanism involving different models such as those of pseudo-second-order, intraparticle diffusion, and Elovich. The isotherms are found to be suitably fitted by the Redlich-Peterson equation, a model including three adjustable parameters and requiring nonlinear least-square analysis. A close agreement exists between the evolution of kinetic, thermodynamic and equilibrium, parameters, indicate chemisorption process. The fact that maximum adsorption occurs at isoelectric point emphasizes the prevalence of the non-electrostatic interaction. The process reflects for D900 a weak chemical interaction via a mechanism of surface complexation. In view of its adsorbed amount, D900 appears very effective for removing reactive dyes from wastewaters.