Mineral salts removal and lithium traces determination in highly concentrated solutions and natural brines

The usual methods, of lithium traces determination, refer in particular to the aqueous solutions whose dry residues do not exceed 7 g L⁻¹. Flame spectrometry or atomic absorption is used for the determination of the considered element.In the case of natural brines, the total dissolved salt ranges from 250 to 350 g L⁻¹. Consequently the determination of lithium traces in this kind of solutions, by the above mentioned spectroscopic methods, may be disturbed due to interferences phenomena. So, a preparatory processing step of the samples is needed.In order to prevent the mentioned phenomena, the total or partial removal of mineral salts, by adding appropriate organic solvent, is carried out. Accordingly, it is significant to make sure that the total quantity of lithium remains in the solution.Therefore, the experimental conditions (sulfate ion removal, solvent ratio and solid-liquid contact time) are optimized. After that the different experimental steps are arranged to make sure the lithium determination, by flame spectrometry, practicable.Finally, the established method is applied firstly to determine Li⁺ in some natural brines and secondly to estimate the lithium reserves in the Tunisian natural brines deposits.     

Crystal packing,vibrational studies,DFT calculations of a new hybrid nickel (II)‐complex and its application in Heck and Sonogashira cross‐ coupling reactions

We particularly investigate a new material [Ni(C₁₂H₁₂N₂)(H₂O)₄]SO₄ that it was hydrothermally synthesized by reaction of 5,5’‐dimethyl‐2,2’‐bipyridne, denoted (dmbpy), metal salt and sulfuric acid. The large crystals are characterized by X‐ray single crystal diffraction, infrared, Raman spectroscopy and DFT calculation. The thermogravimetric analysis indicated that the dehydration occurs in two steps, leading to an anhydrous compound. At room temperature, the complex crystallises in the centrosymmetric space group P2₁/c with the following parameters a = 9.492 (7) Å, b = 9.539 (7) Å, c = 18.411 (1) Å, β =102.616 (1)°, V = 1626.8 (2) ų and Z = 4. The asymmetric unit contains one free SO₄^2‐counter‐ion and [Ni(dmbpy)(H₂O)₄]²⁺ complex cation. The crystal structure of the complex is built up from infinite parallel two‐dimensional planes, containing all the components of the structure and perpendicular to the axis b. The aqua ligands are connected to the sulfate anion via O‐H…O hydrogen bonds that stabilize the three‐dimensional network. The catalytic activity of the complex was examined in the coupling reactions of Heck and Sonogashira in the presence of different bases in various organic solvents under ultrasonic irradiation. The obtained results show that this type of complex can be considered as an effective catalyst for these coupling reactions. The ultrasonic activation results the encouraging yields for a short period of time: 30‐45 min.     

Second structure relation for semiclassical orthogonal polynomials

Classical orthogonal polynomials are characterized from their orthogonality and by a first or second structure relation. For the semiclassical orthogonal polynomials (a generalization of the classical ones), we find only the first structure relation in the literature. In this paper, we establish a second structure relation. In particular, we deduce it by means of a general finite-type relation between a semiclassical polynomial sequence and the sequence of its monic derivatives.     

Chevalley Cohomology for linear graphs

The space of linear polyvector fields on is a Lie subalgebra of the (graded) Lie algebra , equipped with the Schouten bracket. In this paper, we compute the cohomology of this subalgebra for the adjoint representation in , restricting ourselves to the case of cochains defined with purely aerial Kontsevich’s graphs, as in Pac. J. Math. 218(2):201–239, 2005. We find a result which is very similar to the cohomology for the vector case Pac. J. Math. 229(2):257–292, 2007. This work was supported by the CMCU contract 06 S 1502. W. Aloulou and R. Chatbouri thank the Université de Bourgogne and D. Arnal the Faculté des Sciences de Monastir for their kind hospitalities during their stay.     

Hydrogen bonding interactions of pyridine*+ with water: stepwise solvation of distonic cations

The solvation energies of the pyridine*+ radical cation by 1-4 H2O molecules were determined by equilibrium measurements in a drift cell. The binding energies of the pyridine*+(H2O)n clusters are similar to the binding energies of protonated pyridine-water clusters, (C5H5NH+)(H2O)n, which involve NH+..OH2 bonds and different from those of the solvated benzene radical cation-water clusters, C6H6*+(H2O)n, which involve CHdelta+..OH2 bonds. These relations indicate that the observed pyridine*+ ions have the distonic *C5H4NH+ structures that can form NH+..OH2 bonds. The observed thermochemistry and ab initio calculations show that these bonds are not affected significantly by an unpaired electron at another site of the ion. Similar observations also identify the 2-fluoropyridine*+ distonic ion. The distonic structure is also consistent with the reactivity of pyridine*+ in H atom transfer, intra-cluster proton transfer and deprotonation reactions. The results present the first measured stepwise solvation energies of distonic ions, and demonstrate that cluster thermochemistry can identify distonic structures.     

On an unconditional basis of generalized eigenvectors of an analytic operator and application to a problem of radiation of a vibrating structure in a light fluid

In this paper, we prove that the system of generalized eigenvectors of the perturbed operator

T(ε):=T₀+εT₁+ε²T₂+?+εkTk+?,