Evaluation of Relative Photonic Efficiency in Heterogeneous Photocatalytic Reactors

Abstract

The evaluation of photonic efficiency in heterogeneous photocatalysis remains elusive because the number of absorbed photons is difficult to assess experimentally. The photonic efficiency of heterogeneous photocatalytic reactors depends on the reactor geometry, irradiation source, and photocatalyst properties. In this work, the relative photonic efficiency of heterogeneous photocatalytic reactors to degrade an azo dye was evaluated using phenol as the standard system. The experimental tests were carried out in a batch reactor under different conditions of pH, catalyst dosage, initial concentration, and ultraviolet (UV) lamps. The kinetics of disappearance of both phenol and azo dye were studied using the initial rate method and were described according to the Langmuir-Hinshelwood (L-H) kinetic model. It was observed that the relative photonic efficiency depends on the adsorption/desorption properties of the photocatalyst.

Advanced oxidation processes applied to tannery wastewater containing Direct Black 38—Elimination and degradation kinetics

“…The design of the batch reactor has been described in previous papers [14,15]. The annular reactor was irradiated by an 80 W high-pressure mercury vapor lamp and the light intensity was 2.73 × 10 −6 mol s −1 (1.64 × 10 −4 Einstein min −1 ).…”

Photocatalytic Selectivities of Ethane, Methane and Dimethylether Controlled by Reaction Conditions and TiO2 Structure in the Degradation of Acetic Acid

“…Moreover, we have not used the standardization protocol to evaluate relative photonic efficiency for heterogeneous photocatalytic reaction proposed by N. Serpone because, this standardization method is proposed for liquid phase and not for gas phase and that the work of G−C. Netto et al found that this method could be used only if the rate of photocatalytic degradation of substrate and the reference (phenol in this case) presented the same dependence on the parameters affecting the adsorption/desorption properties of the organic substrate on TiO2.…”

Degradation of 4-chloro 2-aminophenol using combined approaches based on microwave and photocatalysis

“…Also production of larger amount of hydroxyl radicals (water splits into OH Å radicals in presence of UV light) gives dominating recombination reaction to form H 2 O 2 which hampers the degradation process. Netto et al [28] studied the degradation of phenol and azo dye under conditions of different UV dissipation power over the range of 80 W to 250 W and reported that the degradation of azo dye continuously increased with an increase in UV power whereas in the case of phenol, the maximum degradation was obtained at 125 W. Chaudhary et al [29] also reported an increased degradation of 2,4-dichlorophenoxyacetic acid with UV power varying from 150 W (19% degradation) to 400 W (99.9% degradation) in 8 h treatment period. Similarly Mir et al [30] reported higher degradation of herbicide derivative, Dinoseb (80%) in the presence of 125 W UV lamp as compared to the 80 W UV lamp (24%).…”

“…1a, it can be seen that the extent of degradation increases with an increase in UV power from 4 W to 8 W and then marginally lower extent of degradation was obtained at UV power of 12 W. Maximum degradation of 49.04% with first order rate constant of 2:18 Â 10 À2 min À1 was obtained at 8 W UV power. The lower rate of degradation of 4C2AP at 12 W UV power can be attributed to the fact that at higher UV power, due to the presence of excessive UV photons, more intermediates (polymeric phenol derivatives) are formed [27] which interrupt the photon attack on the original compound (4C2AP) [27,28]. Also production of larger amount of hydroxyl radicals (water splits into OH Å radicals in presence of UV light) gives dominating recombination reaction to form H 2 O 2 which hampers the degradation process.…”