Simultaneous treatment of gaseous volatile organic compounds and aqueous phenol using a corona discharge reactor

Abstract

Simultaneous treatment of gas and wastewater using a wetted-wall corona discharge reactor was proposed in this research work. Acetaldehyde-laden air and phenol-containing water were chosen as target compounds. Simultaneous treatment of gaseous acetaldehyde and aqueous phenol, and separate treatment of both compounds were thoroughly investigated by experiments. After that, modeling and simulation of the simultaneous system was carried out. Influences of key parameters, namely, inlet acetaldehyde concentration, initial phenol concentration, pH of water, gas flow direction and corona current on removal mechanism and efficiency were investigated. The experimental results show that the simultaneous and separate gas-water treatment could efficiently be achieved. In the simultaneous treatment, when inlet acetaldehyde concentration was lower than 200 mol-ppm, the acetaldehyde was completely removed from the gas stream by absorption via bubbling. Simultaneously, phenol and the acetaldehyde absorbed in water were effectively decomposed by OH radical which was produced by direct contact of the gaseous corona with the interfacial water. In addition, ozone contributed to the partial decomposition of phenol and its byproducts. The above concentration limit of acetaldehyde scarcely affects the decomposition of phenol when the initial phenol concentration was lower than 100 mg L-1. However, decomposition of total organic carbon (TOC) in water was strongly attenuated when acetaldehyde concentration was higher than 100 mol-ppm. This was because acetic acid, the last intermediate mainly obtained from acetaldehyde decomposition, was accumulated in water. In addition, it was found that the decomposition of acetic acid was remarkably increased when the pH was raised up to 11. The developed model and its simulation result for the decomposition of acetaldehyde, phenol and their intermediates were found to be in good agreement with experimental results. The model proposed will be useful for scale-up of the system for practical application. With simultaneous purification, not only can the operating cost, the operation time and the energy consumption be minimized, but the total investment costs for the equipment can also be reduced.