You-Jin Lee

Anodic oxidation of 1,4-dioxane on boron-doped diamond electrodes for wastewater treatment.

A study of the anodic oxidation of 1,4-dioxane, a refractory water pollutant, by boron-doped diamond (BDD) electrodes was carried out under a range of major system variables: initial concentration, current density, temperature, pH, and electrolyte concentration. The 1,4-dioxane removal behavior was monitored by chemical oxygen demand (COD), and the results were compared with theoretical models for the electrochemical incineration of organic compounds. The removal efficiency of COD was shown to be greater than 95% in most cases, and no electrode fouling was observed during the reaction. Experimental degradation behavior agreed well with the theoretical models, implying that system variables can be predicted, even when the process is applied at pilot scale. Processes conducted at lower initial concentrations and higher temperatures yielded better energy consumption efficiency. Conditions of higher current density yielded faster degradation but need greater quantities of charge loading into the system. Therefore, a compromise between treatment time and energy consumption is required to achieve the desired efficiency. Meanwhile, pH and electrolyte concentrations did not affect reaction efficiency, suggesting that pH adjustment prior to wastewater treatment is not necessary. Thus, anodic oxidation of 1,4-dioxane by BDD electrodes promises to be both an economical and an efficient in wastewater treatment process.

Effect of electrokinetic remediation on indigenous microbial activity and community within diesel contaminated soil.

Electrokinetic remediation has been successfully used to remove organic contaminants and heavy metals within soil. The electrokinetic process changes basic soil properties, but little is known about the impact of this remediation technology on indigenous soil microbial activities. This study reports on the effects of electrokinetic remediation on indigenous microbial activity and community within diesel contaminated soil. The main removal mechanism of diesel was electroosmosis and most of the bacteria were transported by electroosmosis. After 25 days of electrokinetic remediation (0.63 mA cm(-2)), soil pH developed from pH 3.5 near the anode to pH 10.8 near the cathode. The soil pH change by electrokinetics reduced microbial cell number and microbial diversity. Especially the number of culturable bacteria decreased significantly and only Bacillus and strains in Bacillales were found as culturable bacteria. The use of EDTA as an electrolyte seemed to have detrimental effects on the soil microbial activity, particularly in the soil near the cathode. On the other hand, the soil dehydrogenase activity was enhanced close to the anode and the analysis of microbial community structure showed the increase of several microbial populations after electrokinetics. It is thought that the main causes of changes in microbial activities were soil pH and direct electric current. The results described here suggest that the application of electrokinetics can be a promising soil remediation technology if soil parameters, electric current, and electrolyte are suitably controlled based on the understanding of interaction between electrokinetics, contaminants, and indigenous microbial community.

Combination of Electrokinetic Separation and Electrochemical Oxidation for Acid Dye Removal from Soil

Abstract The remediation of kaolin soil contaminated with Acid Blue 25 was performed by a combination of electrokinetic separation and electrochemical degradation. The anionic dye was removed from the soil mainly by electroosmosis towards the cathode, with up to 89% removal being achieved at 30 mA for 7 days. The dye solution was completely mineralized in a separate electrochemical oxidation process using a boron-doped diamond anode. A NaCl solution enhanced the oxidation rate of the dye through indirect oxidation mediated by active chlorine, as well as direct oxidation. The results demonstrate that complete removal of dye from soil can be achieved by electrokinetic separation followed by electrochemical oxidation of effluent with a chloride-containing electrolyte.

Electrokinetic Remediation of Soil Contaminated with Diesel Oil Using EDTA–Cosolvent Solutions

Abstract The effect of a chelating agent (EDTA), cosolvent (n-propanol), and non-ionic surfactants (Tergitol 15-S-7 and Tergitol NP-10) as additives in the purging solution for electrokinetic remediation of soil contaminated with diesel oil was investigated. It was found that EDTA functioned as both an electrolyte and a desorbent for hydrophobic organic contaminants. Addition of surfactant with EDTA was not effective for diesel oil transport and removal. The addition of n-propanol and EDTA enhanced hydrocarbon removal efficiency, especially for aromatic hydrocarbons. There was no significant enhancement of removal by use of a combination of EDTA, surfactant and n-propanol relative to the use of EDTA and n-propanol together.

Preparation of Magnetic Fe-Al Binary Oxide and Its Application in Superconducting Magnetic Separation

Iron oxide is widely used for the adsorption of oxyanion and anionic pollutants in water. Incorporation of aluminum expands available Fe oxide surface that can contact with pollutants because amorphous Al oxide exhibits extremely large surface area with porous morphology. Magnetic Fe-Al binary oxide was prepared by adjusting temperature during sintering of the oxides and investigated the feasibility of the magnetic adsorbent for chromate removal from aqueous solution with permanent and superconducting magnets. The Fe-Al oxide was highly magnetized (31.4 emu/g) after sintering at 500 °C. It is considered that the highly magnetized Fe-Al oxide with comparably large surface area can be a good magnetic adsorbent. The initial chromate solution with the adsorbent had 110 NTU of turbidity. After the superconducting magnetic separation with 0.5, 1, and 4 T, the turbidity of the solution decreased to 31.8, 12.3, and 7.7 NTU, respectively. The Fe-Al oxide is an effective magnetic adsorbent that can not only adsorb anionic pollutants, but also be separated by superconducting magnetic separation system.