Energy Efficiencies in a Photo-CREC-Air Reactor: Conversion of Model Organic Pollutants in Air

Abstract

The energy efficiency of the photocatalytic conversion of gas-phase organic pollutants was studied using a redesigned and scaled-up photo-CREC-air reactor. This photocatalytic unit has the unique feature of allowing an accurate analysis of the irradiation field by establishing macroscopic balances and in situ measurements. The photo-CREC-air reactor operates in batch mode with the photocatalyst supported by a stainless steel mesh being irradiated by eight UV lamps. Kinetic modeling was performed, and quantum yields (QYs) and photochemical thermodynamic efficiency factors (PTEFs) were calculated using data for acetone and acetaldehyde photocatalytic degradation in ambient air utilizing a Degussa P25 (Aeroxide 25) photocatalyst. It was found that the photo-CREC-air reactor is suitable for the determination of kinetic and adsorption parameters, given a design with excellent irradiation usage and fluid−catalyst contact. In this respect, quantum yields for both acetone and acetaldehyde exceed the value of 1 (equivalent to 100%), with PTEFs in both cases remaining below the level of 1, as required by thermodynamics.

Immobilized particle coating for optimum photon and TiO 2 utilization in scaled air treatment photo reactors

“…Regarding the organic species adsorbed on the TiO 2 coated mesh at equilibrium, the Langmuir equation provides a good description [32]. On this basis, adsorption isotherms were developed for both TiO 2 -SC and TiO 2 -AAS-ASC meshes.…”

“…This consists of brush spreading sonicated TiO 2 slurry on a mesh followed by drying or calcination. Degussa P25 coated on a mesh using this method showed high photocatalytic degradation of toluene [31], acetone [32,33], isopropanol [34] and acetaldehyde [35]. Despite the advantages of this technique, the search for an improved method is needed.…”

“…The Photo-CREC-Air Reactor is a 55.1 L total volume unit operated in the CREC laboratories [32]. This unit was employed in the present study for the photodegradation of air pollutants.…”

“…The Langmuir model is a good approach to describe the chemisorption at equilibrium [32]. This relates the adsorbed acetone species per unit TiO 2 weight (Q acetone in mole/g of pho- tocatalyst) to the acetone concentration in the gas phase (C Acetone,g in mole/L) as follows:…”

“…(4), can be calculated using an "indirect method" based on the stoichiometric requirements for the oxidation of the observable chemical species [32]. Following this, the "i" lower oxidation state species (C n H m O o ) can be converted with the help of • OH radicals to "h" higher oxidation state species (C x H y O z ) as follows:…”