Photocatalytic Behavior of Na_2ZrTi_5O_(13) sol-gel

摘要

The photocatalytic activity of samples of the new ceramic semiconductor, Na_2ZrTi_5O_(13) sol-gel, was studied using two different reactions, the decomposition (oxidation) of methylene blue and reduction-oxidation of Pb (Ⅱ) from aqueous solutions at room temperature. We synthesised Na_2Ti_5ZrO_(13), which is isostructural to the family of compounds with general formula A_nMTi_mO_(13), (A = Li, Na, K; M = Zr). These materials present a zig zag arrangement forming rectangular tunnels in their structure. The synthesis of this compound was achieved by sol-gel technique using metalic alcoxides at two different pH, 3 and 9. The fresh gels were heat treated at 200°C, 400°C, 600°C and 800°C. The reaction products were characterized by X-ray diffraction (XRD), thermal analysis (DTA, TGA) and infrared spectroscopy (FTIR). The band gap energy (Eg) of each sample prepared was calculated from the UV-Vis absorption spectra.. The values of Eg obtained ranged from 3.5 to 3.2 eV. The best activity found for the methylene blue degradation was performed by the Na_2ZrTi_5O_(13) sol-gel pH 9, treated at 800°C (99%). We assumed that the photocatalytic activity is favored when the structure was already formed. Lead photocatalysed reactions using Na_2ZrTi_5O_(13) sol-gel pH 9, treated at 600°C showed a higher eficiency (98%) than that obtained by TiO_2 (degussa) (85%).