Yuthana Tirawanicahkul, Pichayasuk Chankuson and Supawan Tirawanichakul

pp. 365 - 378

Abstract

Ozone synthesis is one of the applications of near atmospheric plasma processing. An ozone generator in this research comprised two annular cylindrical-shaped electrodes. The inner electrode was made of
stainless steel covered with the dielectric glass and the outer electrode was also made of stainless steel. The electric spacing gap was 0.0075 m and length of ozonizer was 0.21 m. Oxygen gas passing through the discharge gap between two electrodes supplied by an alternating current (AC) high voltage power supply, frequency 50 Hz, ranging of 6-10 kV_AC was used for producing ozone. The amount of ozone was determined by the KI standard method. The result showed that the concentration of ozone is proportional to the AC applied voltage. For determining effect of purified oxygen feed rate of 6-10 L/min on quantity of ozone, the results indicated that at the volumetric flow rate of 8 L/min produced the largest amount of ozone. In addition, ozone concentration at a flow rate of 8 L/min and an electrical discharge time of 3 minutes was
approximately determined as 41, 60, 80 and 135 mg/L at 8, 9, 10 and 11 kV_AC, respectively.
       Moreover, study of dye wastewater of Krajud mat was proposed and treated by three different methods. Firstly, dye wastewater was solely treated by a plasma ozonation. Secondly, a combination of ozonation and alum coagulation was used for dye wastewater treatment. Finally, the combined ozonation and activated carbon adsorption were used for dye wastewater treatment. The experimental results showed that the percentage of light absorbance reduction of pink dyed wastewater for these three different methods was about 56%, 35% and 10%, respectively compared to the reference sample. In addition, For these
methods, the percentage of BOD of treated dye wastewater could be reduced to 64%, 54% and 46% respectively, the percentage of COD could be reduced to approximately 78%, 62% and 27%, respectively, compared to the reference sample. In conclusion, the most effective method for dye wastewater treatment was the combination of ozonation and adsorption by activated carbon.
        For chemical compound analysis, the Fourier Transform Infrared (FTIR) spectrograph illustrated that the treated dye solutions using ozonization were slightly different compared to the reference sample. This is due to some complicated functional groups (methylene, carboxylate etc.) being broken down during ozonation.

Keywords

• activated carbon
• low-temperature plasma
• ozone synthesis
• wastewater