Degradation of 4-Chlorobenzoïc Acid in a Thin Falling Film Dielectric Barrier Discharge Reactor

Abstract

The degradation of 4-chlorobenzoi ̈c acid (4-CBA) in water was performed using an innovative plasma dielectric barrier discharge (DBD) process. The influence of the electrode material directly in contact with the solution was examined. The roles of power and frequency discharge on the treatment efficiency were also evaluated. The hydrodynamic behavior of the solution and physical aspect of the discharge were studied by contact angle measurements and intensified charge-coupled device (iCCD) acquisition, respectively. Analyses showed that the use of stainless steel (SS) resulted in a better efficiency of the process compared with the use of brass (B). The degradation of 4-CBA was 80 and 50% for SS and B, respectively, after 1 h of plasma discharge. The presence of NO x in the plasma discharge and corrosion reaction occurring on the brass surface limited the degradation of the 4-CBA. It was possible to observe two main byproducts and identify the 4-chlorosalicylic acid or 4chlorohydroxybenzoi ̈c acid. Ultimately, the discharge frequency was reduced to limit the production of NO x species.

Electrical Discharge in Water Treatment Technology for Micropollutant Decomposition

“…Nevertheless, very limited information is available in literature on the dependence of the energy efficiency of the sinusoidal frequency for a given reactor design. In the study of Lesage et al [122], no change in energy efficiency was observed for 4-chlorobenzoic acid decomposition with voltage frequency increase from 500 Hz to 2000 Hz for AC powered DBD over moving water film. Increasing AC frequency from 1.5 kHz to 15.6 kHz kept the energy efficiency of a coaxial falling water film DBD reactor in the same order of magnitude as well, in spite of the additional heating that resulted from the higher frequency [172].…”

“…The material of the ground electrode in contact with water in many DBD reactors is, on the other hand, clearly important. In the study of Lesage et al [122], the use of a stainless steel substrate resulted in a better decomposition efficiency in comparison to the use of brass. This is explained with corrosion of the brass substrate under influence of nitrate, leading to formation of aqueous nitrite, which scavenges OH radicals and thus inhibits the degradation process.…”

“…An exotic reactor type where a rod high-voltage electrode with dielectric cover is placed next to a falling water film has been investigated by Lesage et al [122,123] (Figure 5j). The reactor was found to be significantly more efficient than a gliding arc (see Section 3.3.4) over the same falling water film, partly due to less corrosion of the brass substrate in contact with the water.…”

Cold atmospheric plasma technology for removal of organic micropollutants from wastewater—a review

“…The thin water film offers a larger surface to volume ratio than other configurations. The bigger plasma-solution contact surface means higher residence time, hence, more interaction of reactive species with the solution for oxidation reaction [152,153]. Another way to increase the contact surface is the pulsed corona discharge with a wetted-wall type reactor and coaxial geometry [125,128].…”