Use of a low-cost biosorbent to remove pesticides from wastewater.

A lignocellulosic substrate (LS) obtained from our local agroindustry was used as a low-cost and effective adsorbent for the removal of pesticides from wastewaters. The studied pesticides were terbumeton (N-(1,1-dimethyl)-Nethyl-6-methoxy-1,3,5-triazine-2,4-diamine), desethyl terbumeton (N-(1,1-dimethylethyl)-6-methoxy-1,3,5-triazine-2,4-diamine), dimetomorph (4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)acryloyl]morpholine), and isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea). Batch and column experiments were conducted as a function of pH and pesticide concentration under laboratory and industrial conditions. The concentration range studied for the pesticides varied from 2 x 10(-7) to 3 x 10(-4) mol L(-1). The influence of organic and inorganic pollutants was assessed by studying the retention of pesticide in the presence of copper(II) and a surfactant. These experiments indicated that LS is an efficient adsorbent toward the investigated pesticides and has little influence of the other pollutants. The kinetic adsorptions are fast, and the amounts of adsorbed pesticide varied from 1 to 8 g kg(-1) of LS. These retention capacities show that LS can provide a simple, effective, and cheap method for removing pesticides from contaminated waters. Thus, this biomaterial may be useful for cleaning up polluted waters.

Sorption of Cu(II) onto vineyard soils: macroscopic and spectroscopic investigations.

The sorption of Cu on five vineyard soils was examined via macroscopic and spectroscopic investigations. The composition of the soils was previously determined using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). X-ray absorption spectroscopy (XAS) was employed to determine the metal environment with regard to the identity and interaction of the nearest atomic neighbors, the bond distances, and the coordination numbers. The five soils present similar sorption properties and there is no XAS evidence that the nature of the soil samples affects the local chemical environment of Cu(II). The kinetics of the Cu sorption reactions is rapid, with the equilibrium loading of Cu on the surface achieving approximately 200 mumol g(-1), i.e., 12.7 mg g(-1). The XAS data indicate that Cu is adsorbed in the form of inner-sphere complexes with first shell CuO parameters of four equatorial CuO bonds equal to 1.93 A and two axial CuO bonds at 2.43 A. This is in accordance with a Jahn-Teller distorted octahedron environment around copper. Our results provide evidence of the complexation of Cu(II) onto soil organic matter coated with an inorganic surface (quartz, clay, and goethite).

Synthesis, iron(III) complexation properties, molecular dynamics simulations and P. aeruginosa siderophore-like activity of two pyoverdine analogs.

P. aeruginosa ranks among the top five organisms causing nosocomial infections. Among the many novel strategies for developing new therapeutics against infection, targeting iron uptake mechanism seems promising as P. aeruginosa needs iron for its growth and survival. To scavenge iron, the bacterium produces siderophores possessing a very high affinity towards Fe(III) ions such as pyoverdines. In this work, we decided to study two pyoverdine analogs, aPvd2 and aPvd3, structurally close to the endogen pyoverdine. The pFe constants calculated with the values of formation showed a high affinity of aPvd3 towards Fe(III). Molecular dynamics calculations demonstrated that aPvd3-Fe forms with Fe(III) stable 1:1 complexes in water, whereas aPvd2 does not. Only aPvd3 is able to increase the bacterial growth and represents thus an alternative to pyoverdine for iron acquisition by the bacterium. The aPvd2-3 interaction studies with a lipid membrane indicated that they were unable to interact and to cross the plasma membrane of bacteria by passive diffusion. Consequently, the penetration of aPvd3 is ruled by a transport membrane protein. These results showed that aPvd3 may be used to inhibit pyoverdine uptake or to promote the accumulation and release of antibiotics into the cell following a Trojan horse strategy.

Sorption of europium on a goethite surface: influence of background electrolyte.

An experimental and theoretical study of Eu(III) sorption on goethite surface was performed in the presence of different background electrolytes (NaCl, NaNO3, KNO3). Results were described using a simple surface complexation, the double-layer model (DLM), and calculations were performed using either Fiteql3.2 or Jchess codes. The surface acidity constants and sites density were first determined by potentiometric titrations. The influence of electrolyte ions on the value of point of zero charge was studied by both potentiometric and electrokinetic measurements in order to assess their possible retention on goethite. The sorption of Eu(III) was then investigated by the batch method, in the three background electrolytes, as a function of pH. The presence of electrolyte ions was found to decrease the immobilization of Eu on goethite. Sorption results were modelled considering ternary surface complexes (goethite surface/europium/electrolyte ions).

Synthesis, Physicochemical Studies, Molecular Dynamics Simulations, and Metal-Ion-Dependent Antiproliferative and Antiangiogenic Properties of Cone ICL670-Substituted Calix[4]arenes.

Iron chelators, through their capacity to modulate the iron concentration in cells, are promising molecules for cancer chemotherapy. Chelators with high lipophilicity easily enter into cells and deplete the iron intracellular pool. Consequently, iron-dependent enzymes, such as ribonucleotide reductase, which is over-expressed in cancer cells, become nonfunctional. A series of calix[4]arene derivatives substituted at the lower rim by ICL670, a strong FeIII chelator, have been synthesized. Physicochemical properties and antiproliferative, angiogenesis, and tumorigenesis effects of two calix[4]arenes mono- (5a) or disubstituted (5b) with ICL670 have been studied. These compounds form metal complexes in a ratio of one to two ligands per FeIII atom as shown by combined analyses of the protometric titration curves and ESIMS spectra. The grafting of an ICL670 group on a calix[4]arene core does not significantly alter the acid-base properties, but improves the iron-chelating and lipophilicity properties. The best antiproliferative and anti-angiogenic results were obtained with calix[4]arene ligand 5a, which possesses the highest corresponding properties. Analyses of molecular dynamics simulations performed on the two calix[4]arenes provide three-dimensional structures of the complexes and proved 5a to be the most stable upon complexation.

Copper(II) influence on flumequine retention in soils: macroscopic and molecular investigations.

The coadsorption of flumequine (fluoroquinolone antibiotic) and copper(II) on a alkaline soil sample (collected from the Champagne-Ardenne region, France) was studied at macroscopic and molecular scales by means of batch experiments and X-ray absorption spectroscopy. The retained antibiotic amount onto the soil surface increases (from 2- to >20-fold) with the copper concentration due to the formation of a Cu(II)-flumequine ternary surface complex, which leads to the accumulation of flumequine into soils. Flumequine can be classified at environmentally relevant pH values as a slow-mobile compound in soils and a very slow-mobile compound in the presence of copper, even at relatively low concentrations.

Thermodynamic and spectroscopic studies of Cu(II) and Ni(II) complexes with a new proline-threonine dipeptide ligand.

The interactions between a new proline-threonine dipeptide ligand with two metallic cations were investigated in aqueous solution. The metallic cations studied were the copper(II) and the nickel(II), which are involved in many biological processes. The combination of potentiometry, UV-visible spectrophotometry, EPR, and mass spectrometry was used to determine the formation constants of the complexes and their structure in solution. The complexation sites were identified using electronic absorption and EPR spectroscopies. Copper complexes were obtained as square planar or square pyramidal mononuclear species, whereas nickel complexes were obtained as dinuclear species with an octahedral geometry.