Omar Bouras

Cooperative coadsorption of 4-nitrophenol and basic yellow 28 dye onto an iron organo-inorgano pillared montmorillonite clay.

Sorption properties of an iron surfactant-modified pillared montmorillonite (Fe-SMPM) toward two organic pollutants, basic yellow 28 dye (BY28) and 4-nitrophenol (4-NP), were studied at different pH values in both single component and binary pollutant systems. The pseudo-first-order model fits well with the kinetic data obtained in single component studies and sorption capacities of both BY28 and 4-NP increased with the pH value. A sorption synergetic mechanism was observed in binary systems; 4-nitrophenol adsorption was enhanced by the presence of BY28 in the mixture and increased with dye concentrations. Isotherms were described using the Freundlich model in single component systems and the Sheindorf-Rebhun-Sheintuch (SRS) model, an extended Freundlich model, in binary mixtures systems. Hydrophobic interactions between the surfactant-modified pillared clay and the pollutants were suggested to explain the sorption mechanisms.

Using of surfactant modified Fe-pillared bentonite for the removal of pentachlorophenol from aqueous stream.

The first part of this work considers the preparing of the adsorbent type Montm-FeOH-CTAC. After purification of two types Algerian bentonites (Maghnia and Mostaghanem) and preparation of cationic polyhydroxy ferric solution, we have optimized following parameters: CTAC/Montm.-FeOH= 7 mmol.g−1 and pH=3.4, in order to obtain the adsorbent with maximum uptake of PCP. The study of the different experimental equilibrium isotherms showed clearly the high efficiency of these new adsorbents toward PCP, with significant quantities adsorbed especially onto Maghnia samples in acidic environment. Using two mathematical models Langmuir and Freundlich was found to be the Freundlich the best fitted. A comparative study of PCP adsorption onto the two modified clays and an activated carbon in the same conditions has been done.

Fixed-bed column studies of pentachlorophenol removal by use of alginate-encapsulated pillared clay microbeads.

Columns were packed with two alginate/pillared clays microbeads (aluminium-pillared clay and surfactant-modified aluminium-pillared clay). Pentachlorophenol sorption performance was assessed under variable operating conditions: different bed heights, influent pentachlorophenol concentrations and flow rates. These conditions greatly influenced the breakthrough time/volume, the saturation time/volume and the uptake capacity. Higher values of experimental uptake capacities were obtained for the encapsulated surfactant-modified aluminium-pillared clay compared with the encapsulated aluminium-pillared clay, and the values were compared with those obtained with other low-cost sorbents. The experimental breakthrough curves were modelled using Bed Depth Service Time (BDST), Wolborska and Thomas models. Linear relationship was obtained for the BDST model, indicating the suitability of this model; bed capacity increased sharply with the introduction of CTAB in the inorgano-pillared clay. Wolborska model was applied only to the initial part of the curves. Thomas model was no doubt the most suitable description of the adsorption mechanisms for the entire breakthrough curves. Experimental and Thomas model-predicted equilibrium uptake capacities were in accordance.

Removal of sulfacid brilliant pink from an aqueous stream by adsorption onto surfactant-modified Ti-pillared montmorillonite.

A modified hydrophobic and organophilic pillared clay (CTAC-TiH-montm) was prepared by exchanging some Ti polymeric cations into the interlamellar space of one Algerian montmorillonite (montm) and then by co-adsorption of some surfactant molecules such as cetyltrimethylammonium chloride (CTAC). These new materials were used in adsorption of an anionic textile dye: Sulfacid brilliant pink (SAP). According to adsorption isotherms, the organic modification of Ti-montmorillonite clay by CTAC surfactant increases the amount of textile dye fixed to more than 1000 mg g−1. The adsorption experiments showed that a ratio of 3 mmol of CTAC per g of clay and an acidic medium (pH = 4) were the optimal parameters necessary to obtain good adsorption uptake and colourless treated solutions. A comparative study proved the high adsorption capacity of the synthesised adsorbents; they can thus be considered as powerful competitors to activated carbon in the treatment of aqueous textile plants and industry effluents.

Adsorption of basic dyes in single and mixture systems on granular inorganic–organic pillared clays

The adsorption of two basic dyes, CI Basic Yellow 28 and CI Basic Green 4, was studied in single and binary solute systems using two classes of inorganic–organic pillared clay granules as sorbents (300–400 µm and 700–800 µm). These were prepared by high‐shear wet granulation from an Al cetyltrimethylammonium bromide intercalated clay powder (particle diameter < 50 µm). Adsorption rate data indicate that BY 28 adsorbs more rapidly than BG 4 and a pseudo‐first‐order model was found to fit the kinetic curves, with regression coefficients above 0.98. Adsorption isotherms in single solute systems at pH 3 and pH6 were respectively analysed according to the Langmuir and Freundlich models using non‐linear regression. Best fits were obtained with the Langmuir model. In binary dye systems the adsorption at three molar ratios (1:9, 1:1 and 9:1) demonstrated that the adsorption of BG 4 was greater than that of BY 28 on all the sorbents studied; this was in agreement with the results obtained for single solute systems. Increasing the granule size decreased dye adsorption, an effect in accordance with the Sheindorf–Rebuhn–Sheintuch model.

Sorption of basic dyes onto granulated pillared clays: Thermodynamic and kinetic studies

Effect of the granulation process onto the thermodynamic and kinetic sorption parameters of two basic dyes (Basic Yellow 28-BY 28 and Basic Green 4-BG 4) was evaluated in the present work. The charge surface properties of the surfactant-modified aluminium-pillared clay (CTAB-Al-Mont-PILC) particles were not modified, and the isoelectric point remains constant after high shear wet granulation. The Gibbs free energy of both BY 28 and BG 4 sorption was negative and decreased with the granulation; the endothermic nature of the sorption process was confirmed by the positive values of ΔH°. Adsorption kinetics of the two dyes, studied at pH 6 and 150 mg L(-1), follow the pseudo-first order kinetic model with observed rate constants of 2.5-4.2×10(-2) min(-1). The intraparticle diffusion model, proposed by Weber and Morris, was applied, and the intraparticle plots revealed three distinct sections representing external mass transfer, intraparticle diffusion and adsorption/desorption equilibrium. Diffusion coefficients, calculated from the Boyd kinetic equation, increased with the granulation and the particle size. Pseudo-first order kinetic constants, intraparticle diffusion rate constants and diffusion coefficients were determined for two other initial concentrations (50 and 100 mg L(-1)) and include in a statistical study to evaluate the impact of granulation and initial concentration on the kinetic parameters. Kruskal-Wallis tests, Spearmans rank order correlation and factor analysis revealed a correlation between (i) the diffusion coefficients and granulation, and between (ii) the intraparticle diffusion rate constants and initial concentration.

Influence of humic acids on the adsorption of Basic Yellow 28 dye onto an iron organo-inorgano pillared clay and two hydrous ferric oxides.

Effect of humic acids (HAs), macromolecules from natural organic matter, on the adsorption of Basic Yellow 28 is the aim of the present work. Three adsorbents were investigated in this study: an iron organo-inorgano pillared clay and two synthetic Hydrous Iron Oxide (Goethite and HFO). The surface charge was positive in the pH range of this study for the pillared clay; in contrast, it changes from positive to negative when the pH value increased (pH>9) for the two (oxy)hydroxides. Pseudo-first order kinetic rate constants and adsorption capacities increase from humic acid to BY 28. Adsorption isotherms of BY 28 and HA in single component were analysed using the Freundlich equation. Adsorption capacities increased sharply when the pH value of the dye solution was raised from 3 to 9. Increasing the pH medium from 3 to 9 reduces the HA adsorption capacities onto Fe-SMPM and iron oxyhydroxides, respectively. Fitting between measured and predicted sorption capacities of BY 28 and HA in a binary component system indicates that the Sheindorf-Rebuhn-Sheintuch (SRS) model, an extended Freundlich model, is able to describe the simultaneous adsorption of BY 28 and HA. Humic acids favourably affect the adsorption of BY 28, and a cooperative mechanism could be suggested. The synergetic effect existing between BY 28 and HA is shown by the interaction coefficients η12, which are generally high and increase with pH. Some phenomena have been advanced to explain this mechanism.

A modified Sips distribution for use in adsorption isotherms and in fractal kinetic studies

The classical energy distribution introduced by Sips to account for the Langmuir–Freundlich adsorption isotherm is extended to the case when the exponent α of the isotherm is higher than 1. The mean free energy of desorption E0 is estimated from the apparent dissociation constant K by the classical formula E0 = −RT ln K. The dispersion of the energy values, which reflects the heterogeneity of the adsorbing sites, is estimated from the exponent α. The dispersion decreases when the exponent increases. Comparisons are made with the Gaussian approximation and the condensation approximation. The Sips distribution is also applied to activation energies, resulting in a Mittag–Leffler kinetic equation, as used in ‘fractal kinetic’ studies. The adsorption of the dye Basic Yellow 28 onto a surfactant-modified aluminium-pillared clay is studied as an example.

Correction: A modified Sips distribution for use in adsorption isotherms and in fractal kinetic studies

Correction for ‘A modified Sips distribution for use in adsorption isotherms and in fractal kinetic studies’ by Jean Debord et al., RSC Adv., 2016, 6, 66266–66274.