Investigation of Photocatalytic Oxidation and Wet Absorption in a Combined System for Removal of Nitrogen Oxides

Abstract

Background: One of the important achievements of the past decade was the rapid growth of industries and accordingly production of various chemical compounds. Objectives: This study presents a combined system of photocatalytic oxidation and absorption solution to remove nitrogen oxides from polluted air flow. Materials and Methods: The experimental system used in this study comprised a pollutant gas source, mixing chamber, photocatalytic oxidation reactor, wet absorption system, and finally a system for measuring nitrogen oxides. Firstly, by using photocatalytic property, nitrogen oxide was converted to nitrogen dioxide. Then, absorption system was used to absorb nitrogen dioxide into the sodium hydroxide solution. Results: Experimental results have shown that output of nitrogen oxide removal in the initial concentration of 200 ppm was 44% in the beginning of the process and then fixed at 15% during the rest of the process. Also, by changing the amount of zinc oxide nanoparticles from 4 to 8 mg/cm2, no considerable change was observed in the conversion rate of nitrogen oxide. In addition, while the weight percentage of the solution was 5%, the maximum removal of nitrogen dioxide happened. Conclusions: Application of zinc oxide as the photocatalyst can be effective in the removal process.