Heesoo Woo Ph.D. candidate Geotechnical & Geo-Environmental Engineering Lab. Seoul National University

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 2 2 Toxic contaminants, Chlorinated solvents Chlorinated solvents are frequently found as contaminants of soil and ground- water as a result of their widespread use in various industrial processes. Among them, the most frequently released are dichloromethane (DM), chloroform (CF), carbon tetrachloride (CT), trichloroethylene (TCE), and tetrachloroethylene (PCE). TCECT Chlorines in their structure cause the toxicity and the most common solvents are classified as known or suspected human carcinogens.

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 3 3 Toxic contaminants, Chlorinated solvents Dense NAPL Deep depth to the cont. source in subsurface The properties of chlorinated solvents that make them safely remediated include their low degradability and high density.

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 4 4 Zero valent iron (Fe 0 ) PCEEthylene General form: Toxic Less toxic or non toxic Reduction of toxic chlorinated solvents using nZVIs Applications of nZVI particles

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 5 5 Treatment of DNAPL contamination by injection of mobile nZVI particles (Tratnyek and Johnson, 2006) nZVI particles can be transported effectively by the flow of groundwater. Applications of nZVI particles Contamination source can be remediated by injection of mobile nZVI particles in subsurface. Slurry feeding during treatment (© Aquatest, Czech Republic)

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 6 6 Particle agglomeration cause the sedimentation of the nZVI particles. Fe 0 Van der Waals Magnetic force Limitations of using nZVI particles

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 7 7 TEM images of nZVI particles Cluster Limitations of using nZVI particles

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 8 8 Sedimentation of nZVI particles The sedimentation decreases the mobility and reactivity of nZVI particles. Sedimented nZVI particles Limitations of using nZVI particles

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 9 9 Fe 0 Ions DOM nZVIs’ surface oxidation by non-target constituents in groundwater Fe 0 non reactive Fe-oxide layer = Reactivity decrease Cont. Limitations of using nZVI particles

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 10 Geotechnical and Geo-environmental Engineering Lab., Seoul National University 10 Fe 0 Protective layer in order to prevent agglomeration and reactivity loss in groundwater Ions DOM Cont. Protective layer coating onto nZVI particles Fe 0 Protective layer Fe 0

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 11 Geotechnical and Geo-environmental Engineering Lab., Seoul National University 11 Fe 0 Long hydrocarbon chain = steric repulsion = selectivity towards hydrophobic cont. including chlorinated solvents Anchor to metal surface Oleic acid main constituent of olive oil Materials for protective layer

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 12 Geotechnical and Geo-environmental Engineering Lab., Seoul National University 12 Emulsion Microemulsion Transparent μE An emulsion is a mixture of two or more liquids that are normally immiscible. In an emulsion, one liquid is dispersed in the other. Examples of emulsions include milk, vinaigrette sauce. Emulsions or macroemulsions are turbid, have droplet size ranging from 0.2 to 10 μm and may kinetically stable, albeit thermodynamically unstable. Oleic acid and water emulsion can be formed by the aid of appropriate surfactants. = Droplets of oleic acid were dispersed in water phase in the emulsion. Microemulsions are emulsions with particle sizes ranging from 5 to 100 nm. Microemulsions are basically thermodynamically stable, isotopically clear dispersions (transparent or translucent) of two immiscible liquids. Emulsion and microemulsion

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 13 Geotechnical and Geo-environmental Engineering Lab., Seoul National University ~ 200 nm Oleic acid coated nZVI Oleic acid (oil phase) Surfactant Water phase Concept of nZVI microemulsion

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 14 Geotechnical and Geo-environmental Engineering Lab., Seoul National University 14 Mixing above mixture with surfactants at proper ratios Tweens and spans were used as surfactants which are food grades surfactants widely used in food industry nZVI particles in oleic acid High temperature heating (> 200) over 1 h in oleic acid and nZVI mixture 1. Water was added drop by drop until microemulsion was formed Preparation of nZVI microemulsion

Geotechnical and Geo-environmental Engineering Lab., Seoul National University 15 Geotechnical and Geo-environmental Engineering Lab., Seoul National University 15 Oleic acid with Fe 0 particles + Tween 20 + Span 80 + Water Oil phase Surfactants Water phase Results and Conclusions The microemulsions of Fe 0 particles were expected to be prepared using oleic acid, tweens and spans series, and water at proper ratios. Furthermore, the reactivity to chlorinated solvents and transport characteristics in subsurface of the microemulsions have to be confirmed. However, turbidity, stability, and particle size have to be measured in order to confirm formulation of the microemulsions.