Photo catalytic oxidation of TNT using TiO₂-SiO₂ nano-composite aerogel catalyst prepared using sol–gel process

Abstract

The degradation of nitro aromatics like trinitrotoluene (TNT) released in the waste water from explosive process plants is the serious problem due to toxic and explosive nature of TNT. The poor response of TNT to biodegradation enhanced the gravity of the problem. We have demonstrated that high specific surface area TiO₂–SiO₂ nano-composite aerogel is promising photo catalyst in successful treating of TNT contaminated aqueous solution. The TiO₂–SiO₂ composite aerogel with nominal content of 20 and 50% TiO₂, used as catalyst, were prepared by co-precursor sol–gel method using titanium isopropaxide and tetramethylorthosilicate as source of titania and silica, respectively. The XRD studies confirmed formation of anatase phase of crystalline TiO₂ with nano sized crystallites. The TiO₂–SiO₂ aerogel showed specific surface area of 1,107 and 485 m²/g for the aerogels containing 20 and 50% TiO₂, respectively. The 100 ppm TNT solution was treated, in 700 ml capacity reaction vessel, using H₂O₂ oxidizer and TiO₂–SiO₂ aerogel catalyst in presence of UV light (8 W UV lamp). Using TiO₂–SiO₂ (50/50) aerogel with surface area of 485 m²/g, we succeeded to reduce the TOC to 1 ppm within 3.5 h where as using TiO₂/SiO₂ (20/80) aerogel with surface area of 1,107 m²/g, the TOC was reduced to about only 7 ppm in the same time. It revealed that the combination of high TiO₂ content and high specific surface area is an important factor to achieve effective and faster degradation of TNT for complete mineralization.