Photocatalytic degradation of dichlorvos solution using TiO2-supported ZSM-11 zeolite

SILVINA GOMEZ, CANDELARIA LEAL MARCHENA, LUIS PIZZIO Y LILIANA PIERELLA.

Sustainable Energy Developments series

ENGINEERING, WATER & EARTH SCIENCES

Año: 2013; p. 235 - 252

Heterogeneous catalysis involving semiconductors has been developed in the last 10?15 yearsdue to its potential applications to environmental problems (Oancea and Oncescu, 2008). Inrecent years, advanced oxidation processes (AOPs) have been proposed as attractive alternativesfor the treatment of contaminated ground-, surface-, and wastewater containing pesticides ornon-biodegradable organic pollutants (Phanikrishna Sharma et al., 2008a). Among the most usedprocesses are heterogeneous photocatalysis.The semiconductor TiO2 has been widely utilized as a photocatalyst for inducing a series ofreductive and oxidative reactions on its surface (Chong et al., 2010). TiO2 is one of the mostappropriate material due to its high activity in the photodegradation of organic compounds, lowcost, low toxicity, and chemical stability (Fuchs et al., 2009;Yamaguchi et al., 2009). The anataseform of TiO2 is more active generally for the degradation of various organic pollutants thanrutile (Mahalakshmi et al., 2009). The efficiency of TiO2 is influenced by many factors, suchas crystalline structure, particle size, and preparation methods (Hsien et al., 2001). However,poor adsorption and low surface area properties lead to great limitations in exploiting anatase tothe best of its photoefficiency. In addition, technical limitations for adopting this technology areseparation of the catalyst, its reuse and its low quantum efficiency (Phanikrishna Sharma et al.,2008b). On the other hand, supporting TiO2 is commonly reported to be less photoactive due tothe interaction of TiO2 with the support during the thermal treatments and limitations to masstransfer (Mohamed et al., 2005).In the past few years, some efforts have been put in increasing the TiO2 surface area bydispersing TiO2 nanoparticles on high surface area materials. The supports used included silicagels, active carbon, zeolites and clays (Anderson and Bard, 1995; 1997; Hermann et al., 1999;Minero et al., 1992; Torimoto et al., 1997; Xu and Langford, 1997; 1995; Xu et al., 1999;Yoneyama andTorimoto, 2000). Some of these studies have also included an effort to increase theadsorption of organic substrates on the catalyst surface for improving the efficiency of catalyticactivity (Hsien et al., 2001).TiO2 supported on adsorbents provides higher specific surface area and facilitates more effectiveadsorption sites than bulk TiO2 (Anderson and Bard, 1995; Takeda et al., 1997; Torimotoet al., 1997; Xu and Langford, 1995; 1997). Recent research proposed the synthesis of a Fe3+-TiO2 photocatalyst supported on zeolite as an alternative for degradation of dyes (Wang et al.,2011).Zeolites have been investigated as potential supports for photocatalytic systems. They offerseveral distinct advantages over other supports, such as:? Zeolites have cages and channels in the order of 4?14 Å,which can confine substrate moleculesto enhance the photocatalytic reactivity. TheTiO2 molecule can be thus supported on this zeolitematrix.? Zeolites behave as electron donors and as acceptors of