Photochemical treatment (UV/O3+UV/H2O2) of waste gas emissions containing organic pollutants in pilot plant unit

Abstract

A continuous flow photochemical pilot plant unit containing a dry photolytic/photooxidation reactor UV185/ UV254/O3 and an aqueous photochemical UV254/H2O2 reactor was used to remove VOC from the waste gas stream with a high flow rate. The efficiency of this system was thoroughly studied through the control of reaction conditions, the detection of intermediates, and the analysis of reaction products during the degradation of styrene, xylene, and their mixture. The conversion of the model substances depends on the initial concentration of the pollutant, the flow rate, and the type of pollutant. The highest conversion after passing through the whole pilot plant unit was achieved at an initial pollutant concentration 50 ppmv and a flow rate 100 m3 center dot h-1, which is related to the residence time in the system. The conversion of styrene, xylene and their mixture after passing through the whole unit for the 100 m3 center dot h-1 flow rate was 74%, 46% and 52%, respectively. Although the first dry photolytic/photooxidation reactor using UV185/UV254/O3 was more efficient for styrene degradation, the aqueous photochemical UV254/H2O2 part was more suitable for xylene degradation. These experimental results are in the agreement with carbon balance, which confirmed the outlet air contained only unconverted model pollutant (styrene, xylene or their mixture) and CO2. Figures of merit were calculated in order to evaluate the price efficiency of the technology. This study presents an effective AOPs system for the degradation of VOCs from waste gas streams with a high flow rate and provides an insight into their degradation pathways.