Catalytic role of Ti dopant in boehmite for the photodegradation of rhodamine B

摘要

Ti(IV) ions were introduced into the layered aluminum hydroxides via the precipitation of Al(NO3)(3) solution and Ti(C2H5)(4). Catalyst texture and structure were examined by physical techniques: X-ray diffraction, FTIR, SEM, TEM, nitrogen adsorption. Ti(IV) ions were isomorphously substituted for Al(III) species in the boehmite structure in spite of existence of a small amount of amorphous titanium oxide in some cases. The obtained catalysts have layered structure and oblate-shaped platelets with high external surface areas. They were tested for the degradation of rhodamine B (RhB) with air as an oxidant. The intra- and extra-lattice Ti(IV) ions expressed different reaction pathways for the photodegradation of RhB. While octahedrally coordinated Ti(IV) ions in hydroxide layers performed the fast de-ethylation/N-de-ethylation of RhB via consecutive steps, the extra-lattice titanium moieties underwent the slow destruction of chromophores of organic molecules. The Ti-doped boehmite catalysts gave a higher decolorization rate and a better activity in the photodegradation of RhB. The removal efficiency of RhB was obtained at 99% on Ti-intercalated layered hydroxide with molar ratio of Ti/Al = 1/5. The catalysts also expressed a good stability under reaction conditions.