kaolinite and triethanolamine

This work was designed to investigate the sorption equilibrium and kinetics of modified kaolinites of different structural order toward Cr(VI). The key reaction of modification involved an iodomethane quaternization of the mineral previously interlayer grafted with triethanolamine. This induced positively charged centers (PCNs) associated with nitrogens of ammonium salt molecules formed in the interlayer space. The positive charge was compensated by mobile iodide anions which could be ion-exchanged. Results reveal a significant increase in sorption capacity as compared to raw kaolinites and show that the sorption takes place exclusively in the interlayer space which proved to be accessible for the Cr(VI). The amount of sorbed Cr(VI) depends on the PCN content resulting from the kaolinites reactivity influenced by their structural order. An ion-exchange mechanism followed by Cr(VI) to Cr(III) reduction by iodide is proposed. The amount of initially sorbed Cr(VI) and its anionic form is strongly influenced by the pH. Desorption experiments showed that only the Cr(VI) which was not reduced (~30%) was released to the solution.

Topics: Chromium Compounds; Ethanolamines; Hydrocarbons, Iodinated; Hydrogen-Ion Concentration; Kaolin

Raw kaolinite was modified with triethanolamine (TEA), in an attempt to create a new support for the immobilization of metalloporphyrins. Anionic metalloporphyrins containing Fe(3+) or Mn(3+) as metallic centers were immobilized on the prepared support, and the obtained solids were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD), thermal analysis (thermogravimetric and differential thermal analyses--TGA/DTA), and scanning electron microscopy (SEM). The solids were used in heterogeneous oxidation catalysis of cyclooctene and cyclohexane. The yields from the oxidation of cyclooctene depended on the amount of TEA and/or water present in the solids. Good reaction yields were obtained for the oxidation of cyclohexane, with selectivity for the alcohol. In one specific case, a possible co-catalytic activity was verified for TEA during the oxidation of cyclohexane.

Topics: Catalysis; Cyclohexanes; Cyclooctanes; Ethanolamines; Kaolin; Metalloporphyrins; Microscopy, Electron, Scanning; Oxidation-Reduction; Spectroscopy, Fourier Transform Infrared; Thermogravimetry; X-Ray Diffraction