Removal of fipronil by advanced oxidative processes using sulfite activated by cobalt immobilized on silica.

Sulfite auto-oxidation catalyzed by cobalt complexed with ammonia deposited on silica (CoNSi) was used to generate sulfate radicals. The material was characterized by ATR-FTIR, suggesting that the silica structure did not change, and SEM-EDS, indicating an uniform dispersion of cobalt across the material surface according with XRD results. BET analysis provided information on a mesoporous material (type IV isotherm) with regular morphology (H1 hysteresis). The DSC analysis showed that CoNSi is thermally stable under the studied conditions. Quantitative analysis of Fipronil (FIP) was performed by HPLC-DAD, where the applied method was selective and linear. The Box-Behnken experimental design (BBD) method was used to define the best condition for removing the analyte in water. It was found that in 60 min, 76% removal of 1.8 mg L-1 of FIP was reached by adding 0.30 g of the material and 0.30 g of the sulfite in a solution under stirring, aeration, pH 8.0, and room temperature and protected from radiation. However, analysis of cobalt leaching into the solution by FAAS showed a small amount of the metal (0.44 mg L-1) informing that the synthesis of the material must be improved.

A layered mixed zirconium phosphate/phosphonate with exposed carboxylic and phosphonic groups: X-ray powder structure and proton conductivity properties.

A novel mixed zirconium phosphate/phosphonate based on glyphosine, of formula Zr2(PO4)H5(L)2·H2O [L = (O3PCH2)2NCH2COO], was synthesized in mild conditions. The compound has a layered structure that was solved ab initio from laboratory PXRD data. It crystallizes in the monoclinic C2/c space group with the following cell parameters: a = 29.925(3), b = 8.4225(5), c = 9.0985(4) Å, and ß = 98.474(6)°. Phosphate groups are placed inside the sheets and connect the zirconium atoms in a tetradentate fashion, while uncoordinated carboxylate and P-OH phosphonate groups are exposed on the layer surface. Due to the presence of these acidic groups, the compound showed remarkable proton conductivity properties, which were studied in a wide range of temperature and relative humidity (RH). The conductivity is strongly dependent on RH and reaches 1 × 10(-3) S cm(-1) at 140 °C and 95% RH. At this RH, the activation energy of conduction is 0.15 eV in the temperature range 80-140 °C. The similarities of this structure with related structures already reported in the literature were also discussed.