Simultaneous adsorption of chromate and arsenate onto ferrihydrite/alginate composite beads: Competition and mechanism.

Ferrihydrite is an effective adsorbent of chromate and arsenate. In order to gain insight into the application of ferrihydrite in water treatment, macroporous alginate/ferrihydrite beads, synthesized using two different methods (internal and encapsulation processes), were used in this work. The properties of the ferrihydrite were assessed using various techniques, including X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) theory, and zetametry. The results showed that the specific surface area of the ferrihydrite was 242 m2/g, and the PZC was pH8. The kinetic and isotherm adsorption properties of the ferrihydrite were evaluated in this study. The results indicate that the pseudo second-order and Freundlich models accurately describe the kinetic and isotherm adsorption properties of chromates and arsenates. For chromate removal, ferrihydrite exhibited a relatively high adsorption capacity (40.7 mgCr/g) compared to other adsorbents. However, the arsenate adsorption capacity of MFHB-SI (140.8 mgAs/g) was shown to be the most optimal. The internal synthesis process was suitable for arsenate retention due to the resulting arsenate precipitation. The competitive adsorption analyses indicated that the presence of chromate does not limit the adsorption of arsenate. However, the presence of arsenate almost completely inhibits the adsorption of chromate when the arsenate concentration is above 50 mg/L, due to the precipitation reaction of arsenate.

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.

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.

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.

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 microm and 700-800 microm). These were prepared by high-shear wet granulation from an Al cetyltrimethylammonium bromide intercalated clay powder (particle diameter < 50 microm). 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.

Copper and nitrophenol pollutants removal by Na-montmorillonite/alginate microcapsules.

The use of renewable bioresources allows the development of low cost adsorbents that are versatile. In the present paper, the affinity and the removal capacity of montmorillonite/alginate microcapsules for a hydrophobic organic pollutant (4-nitrophenol) and an inorganic pollutant (copper) were evaluated. The physicochemical processes through sorption and kinetic experiments under different ratios of montmorillonite vs. alginate and initial contaminant concentrations were investigated. The total weight loss and diameter decrease during the drying process were 90-96% and 64%, respectively. A significant decrease in beads diameter, related to water elimination, has been observed during the first 24h. Structural modifications that occur during the drying process were evaluated using thermal analysis. From correlation coefficients, the second-order equation depicts properly the adsorption of copper by the microbeads adsorption capacity increases to saturation with time; 3 and 6h were needed to reach equilibrium on wet and dry mixed microcapsules. The pseudo-second order model properly depicts the adsorption process of 4-NP onto Na-mont and (Na-mont/SA) mixed microcapsules but failed to reproduce the data observed for the alginate beads. Isotherms data were fitted with good correlation using the Langmuir model; alginate and montmorillonite adsorption capacities (q(m)/wet beads) agree with those obtained by various studies.

Myriophyllum alterniflorum DC., biomonitor of metal pollution and water quality. Sorption/accumulation capacities and photosynthetic pigments composition changes after copper and cadmium exposure.

Watermilfoil genus Myriophyllum could be used in ecological surveys as in-situ biomonitors of metal pollution and water quality due to its ability to accumulate chemicals. The copper and cadmium sorption characteristics of Myriophyllum alterniflorum have been investigated. The Langmuir and Freundlich isotherms were used to model the metal sorption isotherms and the monolayer sorption capacities, as obtained by the Langmuir isotherm, were determined to be 13.9 mg/g and 11.1 mg/g for Cu2+ and Cd2+ respectively. Results have been compared with previous works on watermilfoils and are in accordance with those obtained on Myriophyllum spicatum. The sorption of the two metals was time-dependent and the kinetics fitted the pseudo-second-order equation well. The data were discussed in terms of ionic radii and HSAB concept. The phytotoxic effects assessed by classical (i.e. changes in biomass, node length) and photosynthetic pigments content endpoints have been investigated using chemometric techniques leading to an effect of cadmium onto photosynthetic pigments.

Dietary phytoestrogens: potential selective estrogen enzyme modulators?

Between one-third to one-half of all breast cancers are steroid sensitive. Steroid-pathway enzymes (sulfatase, 17beta-hydroxysteroid dehydrogenases, aromatase and sulfotransferases) are thus prime candidates for therapeutic approaches based on the control of intacrine activity. Some phytoestrogens, ubiquitous in our diet, are inhibitors of these enzymes. Such a therapeutic potential has stimulated research and progress has been achieved during the last years. Complementary to previous reviews on phytoestrogens, this contribution covers the estrogen pathway inhibition effects of these compounds and special attention will be given to isoflavonoids, flavonoids and lignans. Furthermore, the research on structurally-related compounds as therapeutic agents will be discussed briefly.

Pharmacokinetics and metabolism of apigenin in female and male rats after a single oral administration.

The metabolism of apigenin, a weak estrogenic flavonoid phytochemical, was investigated in the rat. After a single oral administration of radiolabeled apigenin, 51.0% of radioactivity was recovered in urine, 12.0% in feces, 1.2% in the blood, 0.4% in the kidneys, 9.4% in the intestine, 1.2% in the liver, and 24.8% in the rest of the body within 10 days. Sex differences appear with regard to the nature of compounds eliminated via the urinary route: immature male and female rats, like mature female rats, excreted a higher percentage of the mono-glucuronoconjugate of apigenin than the mono-sulfoconjugate of apigenin (10.0-31.6% versus 2.0-3.6%, respectively). Mature male rats excreted the same compounds in an inverse ratio (4.9% and 13.9%, respectively). Radioactivity appeared in the blood only 24 h after oral administration. Blood kinetics showed a high elimination half-time (91.8 h), a distribution volume of 259 ml, and a plasmatic clearance of 1.95 ml/h. All of the parameters calculated from these experiments suggested a slow metabolism of apigenin, with a slow absorption and a slow elimination phase. Thus, a possible accumulation of this flavonoid in the body can be hypothesized.

Metabolism of apigenin by rat liver phase I and phase ii enzymes and by isolated perfused rat liver.

The metabolism of apigenin, a low estrogenic flavonoid phytochemical, was investigated in rat using liver models both in vitro (subcellular fractions) and ex vivo (isolated perfused liver). In vitro, phase I metabolism led to the formation of three monohydroxylated derivatives: luteolin which was the major metabolite (K(m) = 22.5 +/- 1.5 microM; V(max) = 5.605 +/- 0.090 nmol/min/mg protein, means +/- S.E.M.), scutellarein, and iso-scutellarein. These oxidative pathways were mediated by cytochrome P450 monooxygenases (P450s). The use of P450 inhibitors and inducers showed that CYP1A1, CYP2B, and CYP2E1 are involved. In vitro studies of phase II metabolism indicated that apigenin underwent conjugation giving three monoglucuronoconjugates and one monosulfoconjugate. Luteolin led to the formation of four monoglucuronoconjugates, two sulfoconjugates, and one methylconjugate identified as diosmetin. Ex vivo during the apigenin perfusion of an isolated rat liver, none of the phase I metabolites could be recovered. In contrast, two monoglucuronoconjugates and one of the sulfoconjugates of apigenin already identified in vitro were recovered. Moreover, two new derivatives were isolated and identified as a diglucuronoconjugate and a glucuronosulfoconjugate. This work provides new data about the metabolism of apigenin and shows the interest value of using various experimental models in metabolic studies.

Design, synthesis and evaluation of 4-imidazolylflavans as new leads for aromatase inhibition.

Two 4-imidazolylflavans were synthesized and their relative stereochemistry was established by 1H and 13C NMR data. These compounds were tested for their activity to inhibit aromatase. It was observed that the introduction of an imidazolyl group at carbon 4 on flavan nucleus led to potent molecules.

Efficient liquid-phase synthesis of 2'-hydroxychalcones.

The condensation of 2'-hydroxyacetophenone (1) with aromatic aldehydes (2) in a well closed vessel using microwave irradiation or classical heating at 132 degrees C, provides a fast and simple method for the liquid-phase synthesis of 2'-hydroxychalcones without formation of by-products. Antiproliferative activity of these compounds were evaluated using MCF-7 cells.

Synthesis and aromatase inhibitory activity of flavanones.

PURPOSE: Aromatase inhibitors are known to prevent the conversion of androgens to estrogens and play a significant role in the treatment of estrogen dependent diseases such as breast cancer. Some flavonoids have been reported as potent aromatase inhibitors; therefore, in an effort to develop novel anti breast cancer agents, B ring substituted flavanones with a 7-methoxy group on A ring were synthesized and tested to assess their ability to inhibit aromatase activity and to determine the optimal B ring substitution pattern. METHODS: A series of flavanones was prepared by cyclisation of 2'-hydroxychalcones previously obtained by Claisen-Schmidt condensation and the aromatase inhibitory activity of these compounds was investigated using human placental microsomes and radiolabeled [1,2,6,7-(3)H]-androstenedione as substrate. RESULTS: Almost all flavanones exhibited inhibitory effect on the aromatase activity but their potency was dependent on their B ring substitution pattern. Hydroxylation at position 3' and/or 4' enhanced the anti-aromatase activity; thus, 3',4'-dihydroxy-7-methoxyflavanone was found to be twice more potent than aminoglutethimide, the first aromatase inhibitor clinically used. CONCLUSIONS: These results indicated that these flavanones could be considered as potential anti breast cancer agents through the inhibition of aromatase activity and allowed us to select some of these compounds as skeleton for the development of flavonoid structurally-related aromatase inhibitors.

New aromatase inhibitors. Synthesis and inhibitory activity of pyridinyl-substituted flavanone derivatives.

Two (E)-pyridinyl-substituted flavanone derivatives were synthesized and UV irradiation of these compounds afforded a Z-enriched mixture. These products were tested for their ability to inhibit the cytochrome P450 aromatase. It was observed that the introduction of a pyridinylmethylene group at carbon 3 on flavanone nucleus led to a significant increase of aromatase inhibitory effect. Moreover, configuration had a substantial influence on the aromatase inhibitory activity since (E)-isomers were found to be more active than (Z)-isomers.