Jeehyeong Khim

Investigation for Optimization of Ultrasonic Soil-Washing Process for Remediation of Diesel Contaminated Soil

Determination of ultrasonic frequency and experimental design approach to optimization of ultrasonic soil-washing process for remediation of diesel contaminated soil were investigated. Ultrasonic frequencies of 35, 72, and 100 kHz were used for determination of optimal frequency. program was used for experimental design of optimal washing condition. The optimal ultrasonic frequency was 35 kHz. Even though the number of cavitation bubble is little, however cavitation bubbles involving larger energy compared with high frequency was generated. Therefore, the removal efficiency at low frequency was higher than at high frequency. However the input energy has to be considered when the process is applied. The statistical tests from a factorial experiment shows that the application of ultrasound and mechanical mixing are the most important factor for design of an ultrasonic soil washing process. The lab-scale experiments are required to get the optimal condition of ultrasound and mechanical mixing for application of ultrasonic soil washing process.

Effect of initial pH Removal of Dichloroacetonitrile in Photocatalytic Ozonation by Using Compound Parabolic Concentrator Modules

In this study, we investigated to reaction rate of dichloroacetonitrile(DCAN) in each pH(3, 6.5, 10) using heterogeneous photocatalytic ozonation in order to determine optimal pH in photocatalytic ozonation (solar/) process. The results, showed that DCAN was removed at pH of 3, 6.5, and 10 within 4h, and that the corresponding removal rates were 43.8, 91.1, 98.2%, respectively, in the solar/ process. The highest reaction rate was observed at pH 10. These results could be attributed to the self-decomposition of DCAN and the change in the mechanism of the ozone process. Besides, pH 6.5 also achieved a high degradation rate(91.1%) which is due to DCAN adsorbed onto the catalyst surface and reacted with radicals() generated by the reaction between ozone and electron() released from the conduction band of catalyst. The lowest degradation rate was observed at pH 3 due to absence of adsorption and no change in ozone reaction mechanisms.

The Effect of Irradiation Distance/Volume on Sonochemical Oxidation of Arsenite

The objective of this study was to find the frequency that most effectively generates hydroxyl radical and to investigate the effect of solution volume on the oxidation of arsenite (As[III]) under the determined frequency. Based on the cavitation yield for hydrogen peroxide, hydroxyl radical is formed most effectively under the frequency of 300 kHz. The experiment was performed with various solution volumes (334, 690, 1,046, and 1,401 mL) under 300 kHz. Results showed that as solution volume increased, kinetic constant for arsenite oxidation decreased. However, cavitation yield for arsenite decreased in small volumes (334, and 690 mL) but maintained or increased in large volumes (1,046, and 1,401 mL) over a set period of time (10, 30, and 60 min). Based on the kinetic constant result, it is more advantageous to oxidize arsenite in small volumes. However, according to the cavitation yield for arsenite, it is applicable to oxidize arsenite in large volumes over a long period of time.