Anna Hwang

Effect of Ultrasound on Surfactant-Aided Soil Washing

The use of ultrasound as an enhancement mechanism in the surfactant-aided soil-washing process was examined by conducting desoption tests of soils contaminated with naphthalene or diesel-oil. The experiments were conducted to elucidate the effect of ultrasound on the mass transfer from soil to the aqueous phase using naphthalene-contaminated soil. In addition, the use of ultrasound for the diesel-oil-contaminated soil was investigated under a range of conditions of surfactant concentration, sonication power, duration, soil/liquid ratio, particle size and initial diesel-oil concentration. The ultrasound used in the soil-washing process significantly enhanced the mass transfer rate from the solid phase to the aqueous phase. The removal efficiency of diesel-oil from the soil phase generally increased with longer sonication time, higher power intensity, and large particle size.

Degradation of Diethyl Phthalate by Sono-Fenton Process and its Dependence on the Power Density

The first-order rate constants of diethyl phthalate (DEP) degradation by sonochemical, Fenton and sono-Fenton processes were compared, and the synergistic effect of the combined sono-Fenton process and the dependence of the degradation rate on the power density (80, 180, and 330 W L-1) were investigated. The rate constants for the individual sonochemical and Fenton processes were 10-3 to 10-2 and 1.02 ×10-2 min-1, respectively. The synergy from the combined process increased significantly as the applied power density increased, and it was 1.97 with the input of ultrasonic energy of 330 W L-1. This increase was attributed to the higher efficiency of hydroxyl radical production from several pathways. The relationship between the degradation rate constant and power density was linear because the cavitation rate increased with increasing power level of the applied ultrasound.

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.

Evaluation of Hydroxyl radical Formation and Energy Distribution in Photolysis Reactor

In this study, photochemical effects (OH radical formation) in the photoreactor was investigated to analyze UV-C intensity distribution. In addition, The influence radius of the UV-C lamp was measured at various dose of (Degussa P-25). The photoreactor used in this study was bath type reactor which is made by acrylic and the UV-C lamp (SANKYO DENKI, wavelength : 254 nm, Diameter : 2.2 cm, Length : 18.5 cm) was used as photo source. The maximum electric power consumption of the UV lamp was 10.5 W. The OH radical formation by UV-C was measured by KI dosimetry methods. From the results, the effective OH radical formation was occurred under the following condition. The reasonable distance of UV-C lamp is within 13 cm and the intensity of UV-C lamp should be more than 0.367 mW/. Moreover, the concentration of catalyst affects on the influence radius of the UV lamp.

Study of Degradation of Bisphenol A with

In this study, photocatalytic degradation and mineralization of bisphenol A (BPA), which has been listed as one of endocrine disruptors, were carried out in the CPC system using slurry and UVA irradiation. The degradation efficiency has been investigated under the controlled parameters including initial concentration (5, 10, 20 mg/L), dosage of (0.1, 0.5, 1.0 g/L), UVA power (0, 80, 120 W) and temperature (0, 20, 30). At 10mg/L of initial concentration, BPA was degraded above 80% after 10min, BPA were degraded 97% and 49% at 20 mg/L and 30 mg/L, respectively. At dosage was 0.1 and 0.5 g/L, the degradations of BPA showed similar trend and were about 70% after 1 hr, and the degradation of BPA was above 80% after 30 min at 1 g/L of dosage. The increase of degradation seem to be due to the increase in the total surface area, namely number of active sites, available for the photocatalytic reaction as the dosage of photocatalyst increased. When the UVA power was 120 W, BPA was degraded rapidly above 60% after 10min of reaction time. To investigate the effect of temperature, carried out experiment controlled temperature, there were no significant differences depending on the temperature. After 1hr, the degradation of BPA were 46%, 67%, and 69% at 10, 20 and .

TiO_2

In this study, phosphatic clay was used as a phosphate-containing material. The phosphorus was fractionated by CRM BCR-684 protocol, and inorganic phosphorus, mostly apatite phosphorus, was determined to be the major form. The elemental composition of the phosphatic clay was identified using X-ray fluorescence (XRF) spectrometry and the main compositions were CaO and P2O5. The specific surface area, pore volume and average pore diameter were also measured. The leaching test results showed that the phosphate in the phosphatic clay was easily dissolved to aqueous phase, enabling the phosphate clay to be used as a source material for the immobilization process of heavy metals.