F.V. SILVA†, M.A. LANSARIN† and C.C. MORO‡ † Chemical Engineering Department, Federal University of Rio Grande do Sul (UFRGS) R. Eng. Luis Englert, s/n. CEP: 90040-040 - Porto Alegre - RS - BRAZIL, Solids and Surfaces Laboratory. Institute of Chemistry, Federal University of Rio Grande do Sul (UFRGS) – Postal Box 15003; CEP 91501-970 - Porto Alegre – RS – BRAZIL, Abstract The photocatalytic degradation of to significant additional costs in reactor operation.
phenol was studied using slurry and immobilized However, the use of immobilized catalysts in
photocatalytic reactors can simplify their operation and 2 as catalysts in order to compare the specific re-
action rate constants, k
s and kp. Losses from phenol
evaporation, the time necessary to reach adsorption
Several studies have compared the decomposition of equilibrium, irradiation effects and photolysis rates
substrates using suspended and immobilized catalysts were quantified. k
(Li et al., 2010; Grieken et al., 2009; Scotti et al., 2009; s was determined under rate-
optimizing operating conditions, and k
Ochuma et al., 2007a; Cho et al., 2005; Ling et al., p was deter-
mined using the amount of immobilized catalyst 2004; Mehrotra et al., 2005; Dijkstra et al., 2001).
mass that gave the maximum pollutant degradation
However, these studies reached different conclusions. Slurry systems were variously reported to be more effi- s was two times larger than kp when the cal-
culations were made on catalyst mass basis. Experi-
cient, less efficient, and as efficient as the immobilized ments performed to study catalyst deactivation systems.
showed that k
To assist in the scaling-up of photocatalytic reactors, p was approximately one-half of its ini-
tial value after 18 hours of phenol photodegradation.
this study aims to establish the differences between the Also, among the photocatalytic degradation reac-
effects of suspended and immobilized catalysts on the tions of rhodamine B, tetracycline and phenol, the
ratio of k
Preliminary experiments were carried out to confirm s to kp was between 2.1 and 5.3 when the
calculations were made on catalyst mass basis.
that the disappearance of phenol was only caused by Keywords Phenol; Rhodamine B; Tetracycline;
photocatalytic degradation. To test this, phenol losses Photocatalysis; TiO
by evaporation, the time to reach the adsorption equilib- rium, irradiation effects and photolysis rates were meas- I. INTRODUCTION
ured. The optimum catalyst loading conditions for the Many studies of the photodegredation of phenol cata- adopted configuration were then identified, and the re- lyzed by TiO2 illuminated with UV and near-UV light action rate of the slurry batch reactor was determined. have been reported, and the phenol degradation path- Measurements of the slurry catalyst were compared to ways in the UV/TiO2 system are well documented (de those of the immobilized catalyst. Catalytic activity Lasa et al., 2005; Gorska et al., 2009). The data in Table 1 indicate pseudo-first order kinetics for phenol photodegradation in slurry reactors. Even in studies em- II. METHODS
ploying identical catalysts and initial phenol concentra- All measurements presented in this work were repeated tions, the reported pseudo-first order specific reaction three times, and the averages of the observations are re-rate constants differ significantly, limiting the useful- A. Materials and reactants
The studies presented in Table 1 were conducted in Experiments were carried out in a 1 L glass cylindrical slurry reactors. When slurry reactors are operated as reactor, which was jacketed, covered with aluminum photocatalytic reactors, the catalysts must be kept sepa- foil and enclosed in a wooden box with a built-in fan. rate from the degraded products; this requirement leads Table 1: Literature values of phenol photocatalytic degradation using batch slurry reactors with TiO2.


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