Seong-Hye Kim

Degradation of trichloroethylene (TCE) by nanoscale zero-valent iron (nZVI) immobilized in alginate bead.

Nowadays, many researchers have studied the environmental application of the nanoscale zero-valent iron (nZVI) and several field applications for the groundwater remediation have been reported. Still, there are many concerns on the fate and transport of the nZVI and the corresponding risks. To avoid such concerns, it was investigated to immobilize nZVI in a support and then it was applied to degrade trichloroethylene (TCE). The nZVI and palladium-doped nZVI (Fe(0)- and Fe/Pd-alginate) were immobilized in the alginate bead where ferric and barium ions are used as the cross-linking cations of the bead. According to TEM (transmission electron microscopy), the size of the immobilized ZVI was as small as a few nanometers. From the surface analysis of the Fe/Pd-alginate, it is found that the immobilized nZVI has the core-shell structure. The core is composed of single crystal Fe(0), while most of irons on the surface are oxidized to Fe(3+). When 50 g/L of Fe/Pd-alginate (3.7 g Fe/L) was introduced to the aqueous solution, >99.8% of TCE was removed and the release of metal from the support was <3% of the loaded iron. The removal of TCE by Fe/Pd-alginate followed pseudo-first-order kinetics. The observed pseudo-first-order reaction constant (k(obs)) of Fe/Pd-alginate was 6.11 h(-1) and the mass normalized rate constant (k(m)) was 1.6 L h(-1) g(-1). The k(m) is the same order of magnitude with that of iron nanoparticles. In conclusion, it is considered that Fe/Pd-alginate can be used efficiently in the treatment of chlorinated solvent.

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.