Kinetic and thermodynamic effects during the adsorption of heavy metals on ETS-4 and ETS-10 microporous materials

摘要

ETS-10 and ETS-4 microporous materials were synthesized in presence of tetralkylammonium (TAA) ions from gels of molar composition w Na2O-0.10 TAABr-1 SiO2-z TiO2-0.6 KF-1.28 w HCl-39.5 H2O with TAA = tetramethyl-, tetraethyl-, tetrapropyl- and tetrabutyl-ammonium in hydrothermal conditions at 190 A degrees C. The TAA ions enter the microporous channel of ETS-10, while they cannot penetrate the void spaces of ETS-4. The ETS-10 microcrystals are all cubic, while the ETS-4 crystals are laminar and irregular. The microporous volume of ETS-10 is equal to 0.11-0.13 cm(3) g(-1), the microporous volume of ETS-4 is very small, 0.002-0.008 cm(3) g(-1). The ion exchange of Cs+, Cd++, Pb++ and Hg++ ions using their corresponding nitrates show kinetic effects, i.e. the efficiency of ion exchange is higher at 1 than 2 h, the thermodynamic equilibrium. For ETS-10, partially dehydrated cations intervene in the ion exchange, while for ETS-4 well dehydrated ions can only penetrate the available pores.