Photocatalytic treatment of indoor air: Optimization of 2-propanol removal using a response surface methodology (RSM)

Abstract

This paper presents an experimental design methodology for the optimization of the photocatalytic removal of 2-propanol also called isopropyl alcohol (IPA) at indoor air concentration level (ppbv). The response surface methodology (RSM) for the modelization and optimization of the photodegradation of 2-propanol in the presence of titanium dioxide was used. The effect of four different process parameters on the yield of 2-propanol mineralization was determined. Experiments were performed using an annular flow-through reactor with TiO2 as photocatalyst, 2-propanol as a volatile organic compound (VOC) model, under different ranges of relative humidity (RH: 0–60%), inlet concentration (100–700ppbv) and flow rate (100–500mLmin−1), TiO2 loading (5–20gm−2). Analysis of reaction intermediates was conducted using an automated thermal desorption technique coupled with gas chromatography–mass spectrometry (ATD–GC–MS) whereas a gas chromatograph equipped with a pulsed discharge helium photoionization detector (GC–PDHID) was used for on-line measurements of CO and CO2 at ppbv level. RH was found as the principal parameter that affect significantly the mineralization and the formation of acetone, the principal reaction intermediate from the photocatalytic oxidation of 2-propanol. For example an immediate and total removal of 2-propanol at very low % of RH along with a high rate of mineralization without any by-products was found. Many strong interactions between the parameters were also found ([2-propanol]–flow rate, RH–[TiO2], [2-propanol]–RH). The model obtained (R2=0.9965) shows a satisfactory correlation between the values of experimental data and predicted values of 2-propanol mineralization (CO2).