Preparation Of Anion Doped TiO₂ Catalyst And Primary Research Of The Photocatalystic Degradation Mechanism Of 2, 4, 6-Trinitroresorcinol

As a kind of advanced oxidation processes, TiO₂ photocatalysis is being deeply andwidely studied recently. The key of the research focuses on the improvement ofphotoreaction activity of TiO₂ catalyst and the kinetics of degradation of the organicpollutants. Both are the precondition and foundation of the practical applications of TiO₂photocatalysis.To improve photocatalytic ability of TiO₂ catalyst, nonmetal ion S, N were involved inthe crystal lattice of TiO₂ which brought about the visible-light sensitization of TiO₂. Toevaluate the photocatalytic activity of sampies, the photooxidation of 2,4,6-trinitroresorcinol (styphnic acid) was carried out in a series of experiments. In this paper,we have studied the photocatalytic degradation of aqueous solutions of 2,4,6-trinitroresorcinol in the presence of aerated TiO₂ suspensions in order to establish thepossible reaction pathways leading to the mineralization of the compound. The primarystudy was listed as following:(1) The highly effective, great surface area and doped sphericity TiO₂ catalySts wereobtained through the precipitating action between urea and Ti(SO₄)₂. The catalysts wereobtained through ultrasonic separation and calcined at air at the temperature of 400℃ofthe deposit, which was generated in the reaction of Ti(SO₄)₂ and urea. Obtained catalystswere typically anatase phase TiO₂ with the average crystallite size about 18.0±2.0 nm. Thesurface area of obtained catalysts was as much again of commercial TiO₂, pore volumewas much larger and average pore size was smaller than commercial TiO₂. Moreover, thelight absorption of prepared catalysts showed red-shift and absorption region has beenenlarged to visible light region. The highly orderliness of the surface structure of obtainedcatalysts improv the absorbant ability of the pollutant. The existence of N, S changes thesurface structure of catalysts, which consequently reduces the chance of recombination ofphoto-induced electrons and holes and decreases the band energy of catalysts. Accordingly,the catalysts show excellent photocatalytic activity under the irradiation of UV and visiblelight.(2) The photocatalytic degradation of 2, 4, 6-trinitroresorcinol in oxygenated aqueoussuspensions containing obtained TiO₂ leads to the complete mineralization of the substrate.The photodegradation of 2, 4, 6-trinitroresorcinol seems to occur in two steps: a rapid onedestroying the aromatic group, followed by a much slower oxidation of the aliphatic chains.The formation of inorganic nitrogen species is the result of the denitration of the nitrophenols.The hydroxyl radical oxidation is the major reaction pathway in the photocatalyticdegradation of the substrate. Nitrite ions are formed in the early stages of the process,whereas nitrate and ammonium ions are present at the end of the degradation. Theformation of ammonium ions implies that reductive pathways are also significant under theexperimental conditions used in this work.