The decolorization of 180 microM aqueous solutions of
Acid Orange 7 (AO7) by means of a non-
thermal plasma technique (i.e., the gas-liquid gliding
arc discharge, which is generated between at least two
metal electrodes with AC high voltage) was investigated in this paper. The effects of the plasma treatment time and the type of feeding gas, including air,
oxygen,
nitrogen and
argon of the
dye removal were determined. It is found that the voltage cycles of the gas-liquid gliding
arc discharge are characterized by a moderate increase in the tension which is represented by a peak followed by an abrupt decrease and a current peak in the half period (10 ms); the concentration of AO7
solution decreases exponentially to reach 58.9, 77.4, 89.1, 95.1 and 99% in 25, 50, 75, 100 and 125 min, respectively, and the ln(Ct/C0) varies linearly with the treatment time t, indicating that decolorization reaction follow first pseudo-order kinetics with a constant rate of 0.03327 min(-1) when air was used as feeding gas; the decolorization rate during the plasma treatment is the greatest for
oxygen as the feeding gas, in turn followed by air and
argon, and was the least when using
nitrogen. The variations of pH and conductivity and the formations of
hydrogen peroxide and
ozone are measured.