Sepiolite/TiO2 and metal ion modified sepiolite/TiO2 nanocomposites: synthesis, characterization and photocatalytic activity in abatement of NOx gases

Un-exchanged and Zn or Cu ion exchanged samples of a newly discovered sepiolite clay from Greece were combined with nanophase anatase titania for the synthesis of sepiolite based nanocomposites and tested for oxidation of NOx gases. The Zn or Cu ion exchanged clay was modified by replacing the exchangeable cations with Zn or Cu ions. Three separate single phase sepiolite samples were prepared, i.e., the sepiolite (S), the one modified with Zn (Zn-S) and the one modified with Cu (Cu-S). Additionally, three nanocomposites were synthesized combining the above three sepiolite samples with TiO2 in weight ratios of 30:70 and named S-TiO2, Zn-S-TiO2 and Cu-S-TiO2, respectively by depositing TiO2 (anatase) on the sepiolite surfaces using titanium isopropoxide as a precursor under hydrothermal treatment at 180 degrees C. The phase composition, particle morphology and physical properties of the sepiolite samples and the nanocomposites were characterized by XRD, ATR-FTIR, TEM, DRS-UV Vis and N-2-sorption/desorption analyses. The photocatalytic activity of all the clay mineral-titania nanocomposites was examined in the decomposition NOx gases. Sepiolite and especially Zn modified sepiolite based nanocomposites showed better photocatalytic activity for the oxidation of NOx gases compared to that of reference photocatalyst titania P25 under UV-light irradiation.