Mesoporous Nanospheres of Titania Directly Modified with Tungstosilicic Acid as Catalysts in the Photodegradation of 4-Chlorophenol

JULIAN ANDRES RENGIFO-HERRERA; ROMINA FRENZEL; EDGARDO L. SOTO,; MIRTA N. BLANCO; LUIS R. PIZZIO

Comprehensive Guide for Mesoporous Materials, Volume 2: Analysis and Functionalization

Nova Science Publishers

Lugar: Nueva York; Año: 2015; p. 99 - 134

A series of mesoporous titania materials modified with with tungstosilicic (TSA) were successfully synthesized using titanium isopropoxide as titania precursor and urea as low-cost template via sol-gel reactions. They were characterized by FT-IR, XRD, DTA-TGA, DRS, SEM and BET. The obtained mesoporous solids presented an average pore diameter higher than 3.1 nm. The specific surface area decreased when the TSA amount and the calcination temperature increased. The XRD patterns of the modified samples only exhibited the characteristic peaks of anatase phase. The presence of TSA retarded the crystallization of the anatase phase and its transformation into rutile phase. The FT-IR studies showed that the main heteropolyoxometallate species present in the composites is the [SiW12O40]4- anion for the samples calcined up to 500 ºC. The band gap energy slightly decreased as a result of the introduction of TSA into the titania matrix, though it remained almost constant with the calcination temperature increase. The 4-chlorophenol degradation behavior of the catalysts as a function of time depended on the TSA amount and the thermal treatment temperature. The amount of degraded 4-CP increased with the increment of TSA content being the sample containing 30 % TSA calcined at 600 ºC the most active. The apparent reaction constant, estimated assuming a pseudo-first-order kinetics, followed the same trend. The catalysts can be reused at least three times without an important decrease in the degradation and mineralization degrees.