Synthesized and characterization of organobentonites for anionic dye removal: application to real textile effluent.

Clays have been considered as potential alternative adsorbents due to their high adsorptive property, abundance and non-toxic compounds. Adsorption of cationic dyes by natural clays has been studied and appreciable results have been reported, but few researchers have been interested in anionic dyes. Anionic dyes are widely used by the textile industries, yet they are toxic, non-biodegradable and hardly adsorbable on natural clay; modified clay (e.g. organoclay) has emerged as an alternative adsorbent. In this study, organobentonites were prepared with hexadecyltrimethylammonium bromide at three cation exchange capacity levels and used as adsorbents for the removal of, reactive blue II - an anionic dye used in Tunisian textile industry to dye jeans. Obtained organobentonite-labelled Hi-bent (I = 1, 2 and 3) was characterized by several techniques in order to study the effect of a surfactant on texture and structure of the initial clay. H3-bent and purified bentonite (Na-bent) were then tested as adsorbents. The amount of dye removal by H3-bent (98%) was found to be around five times higher than that of Na-bent (19%). Adsorption process was well described by Freundlich, Dubinin-Radushkevic and Elovich isotherms model. Kinetic data were fitted by both pseudo-second-order and pseudo-first-order models. The use of Na-bent, as adsorbent, for real textile effluent treatment was tested, and significant results related to two other clay minerals were obtained.

Antioxidant activities, anticancer activity and polyphenolics profile, of leaf, fruit and stem extracts of Pistacia lentiscus from Tunisia.

Plant derived compounds have played an important role in the development of several clinically useful anticancer drugs. The aim of the present study was 1) to evaluate for the first time the anti-proliferative activity of a polyphenol enriched extract obtained from leaf, fruit and stem of Tunisian variety of Pistacia lentiscus against two cultured cancer cells, and 2) to carry out a phytochemical analysis of vegetable extracts particularly by determining the chemical composition of phenolics (total polyphenols, flavonoids and condensed tannins content in solvents with varying polarities), 3) to  evaluate the antioxidant activity and identify the major compounds by RP-HPLC. Leaf extract using methanol/water (8:2) showed the highest polyphenol content (124.1 mg GAE/g DW). Moreover, total antioxidant capacity, reducing power and antiradical capacities against DPPH were maximal in leaf extracts with IC50 significantly lower than that standard (BHT). In MTT assay, methanol (8:2) extract exerted the most potent cytotoxic effect. The leaf extract exhibited an important antiproliferative activity (IC50: 135.67 ± 2.5 and 250.45 ± 1.96 µg/ml in CaCo2 and AGS cells respectively) but the infusion extracts of fruit stems and leaves were inactive. The RP-HPLC analysis revealed the presence of several phenolic compounds in P. lentiscus leaf, fruit and stem including tannic acid, gallic acid, digalloyl quinic acid derivative, quercetin and   p-coumaric acid as major phenolics. The high phenolic content and the important antioxidant activities of P. lentiscus extract could be a useful source of natural products and may be increasingly important for human consumption, prevention of damages caused by oxygen free as well as for the agro-food, cosmetic and pharmaceutical industries.

Adsorption of lead onto smectite from aqueous solution.

The purpose of this research is to study the effect of a new method of adsorption using membrane filtration to determine the maximum amount of lead adsorbed by clay and investigate the behavior of the clay after adsorption of the said metal. Treatment of wastewater contaminated with heavy metals depends on the characteristics of the effluent, the amount of final discharge, the cost of treatment, and the compatibility of the treatment process. The process of adsorption of heavy metals by clays may be a simple, selective, and economically viable alternative to the conventional physical-chemical treatment. This is justified by the importance of the surface developed by this material, the presence of negative charges on the said surface, the possibility of ion exchange taking place, and its wide availability in nature. The removal of lead from wastewater was studied by using the adsorption technique and using clay as the adsorbent. A method was optimized for adsorption through a membrane approaching natural adsorption. This new method is simple, selective, and the lead adsorption time is about 3 days. The various properties of clay were determined. It was observed that the cation exchange capacity of the clay was 56 meq/100 g of hydrated clay for the raw sample and 82 meq/100 g for the purified sample. The total surface area determined by the methylene blue method was equal to 556 and 783 m(2)/g for the raw and purified samples, respectively. The adsorption kinetics depends on several parameters. The Pb(II) clay, obeys the Langmuir, Freundlich, and the Elovich adsorption isotherms with high regression coefficients. The use of this adsorbent notably decreases the cost of treatment. It was concluded that clay shows a strong adsorption capacity on Pb(II), the maximum interaction occurring with purified clay treated at high concentration of lead. It is proposed that this adsorption through a membrane be extended for the treatment of effluents containing other metals.

Structural and luminescent properties of new Pb(2+)-doped calcium chlorapatites Ca(10-x)Pb(x)(PO(4))(6) Cl(2) (0≤x≤10).

Excitation and emission spectra of Pb(2+) ions in Ca(10-x)Pb(x)(PO(4))(6)Cl(2) (0≤x≤10) compounds are investigated for various activator concentrations at different temperatures. A calcium-lead chlorapatite system shows a common apatitic structure and occurs as a continuous solid solution. An attempt to identify the pure electronic transitions between the ground and the excited levels of Pb(2+) is made. As a consequence of the two different sites in the apatite, two emission bands due to the [Formula: see text] (at room temperature) and [Formula: see text] (at low temperature) transitions of the Pb(2+) ions are observed. Decay times of Pb(2+) emission have been measured. Experimental data point out thermalization between (3)P(1) and (3)P(0) levels, for example, at very low temperature, the forbidden transition [Formula: see text] is the most intense. The overlap between the emission band of one site and the excitation band of the other site corresponds to an energy transfer phenomenon. Correlations between the luminescence results and the structural data are discussed.