Anne Boos

Synthesis and Characterization of Mesostructured Silica Doped with Acyl‐Hydroxy‐Pyrazole Derivatives. Sorption Tests of Cu(II) and Eu(III)

Abstract The synthesis and the characterization of mesostructured silica doped with acidic acyl‐hydroxy‐pyrazoles like extractants are described. The extractants have either a single chelating site, 1‐phenyl‐3‐methyl‐4‐stearoyl‐5‐hydroxy‐pyrazole (HPMSP), or two chelating sites, 1,12‐bis(1′‐phenyl‐3′‐methyl‐5′‐hydroxy‐4′‐pyrazolyl)‐dodecane‐1,12‐dione (HL‐10‐LH). The so‐called doped silicas were synthesized in basic medium according to a sol‐gel process beginning with the solubilization of the extractant in a micellar phase followed by the precipitation of silica around micelles. The chemical composition of the synthesized materials, especially the ligand content, was determined. High quantities of ligand loadings (up to 0.69 mol/kg) are reached. The materials obtained were characterized by X‐ray diffraction, laser granulometry, transmission and scanning electron microscopy and, after calcination, by nitrogen physisorption. Un‐doped silica is mesostructured, lamellar, and has high pore diameter as well as high specific surfaces. Doping induces the disorganization of the lamellar structure, the increase of the pore diameter, and a slight decrease of the specific surface. The capacities of extraction of Cu(II) and Eu(III) by the doped materials and the corresponding extraction rate were measured: high values are reached.

Solid‐Liquid Extraction of Lanthanum(III), Europium(III), and Lutetium(III) by Acyl‐Hydroxypyrazoles Entrapped in Mesostructured Silica

Abstract The solid‐liquid extraction of lanthanum(III), europium(III), and lutetium(III) by mesostructured silicas doped with 1‐phenyl‐3‐methyl‐4‐stearoyl‐5‐pyrazolone (HPMSP, bearing one chelating site) or with 1,12‐bis(1′‐phenyl‐3′‐methyl‐5′‐hydroxy‐4′‐pyrazolyl)‐dodecane‐1,12‐dione (HL‐10‐LH, bearing two chelating sites) has been studied and compared to the analogous solvent and micellar extractions in terms of the stoichiometry of the extracted complex and of the extraction efficiency. The solid‐liquid extraction order in the lanthanoid series is La<Eu<Lu; it is the usual liquid‐liquid extraction order obtained with acidic extractants. A theoretical model is used to determine the stoichiometries of the extracted complexes and the extraction yield is measured as a function of the pH, of the extractant/metal ratio (S/M) and of the volume ratio of the two phases (φ). For HPMSP, the extracted complexes involve three ligand molecules for one metal. For HL‐10‐LH, the complex stoichiometries are found to be either Ln(L‐10‐L)(L‐10‐LH) (Ln=La, Eu) or Lu2(L‐10‐L)3 for S/M=25, or Eu2(L‐10‐L)3 for S/M=5. For the first time, the synergistic solid‐liquid extraction is studied after a successful attempt at simultaneously immobilizing both extractants HL‐10‐LH and 2,4,6‐tri(2‐pyridyl)‐1,3,5‐triazine, “TPTZ”, into silica; the complex extracted in this case differs from the one obtained in solvent extraction.

Surfactant-templated silica doped with 1-phenyl-3-methyl-4-stearoylpyrazol-5-one (HPMSP) as a new sorbent

A new sorbent for transition elements was prepared in a one-step synthesis by encapsulation of a pyrazolone ligand in a surfactant-templated silica. This new material was characterized by X-ray diffraction (XRD), nitrogen physisorption and transmission electron microscopy (TEM). The material presents a lamellar symmetry with a pore diameter of 39 A. The use of a cationic surfactant allows a high loading of ligand (0.43 mol kg−1), associated with complete accessibility of the ligand to the aqueous phase. A sorption capacity of 0.2 mol kg−1 was observed for copper ions in a NaNO3 0.01 M medium. Complete elution of copper species is possible with HNO3 1 M.