Tae-Soon Kwon

Extraction behavior of As, Pb, and Zn from mine tailings with acid and base solutions.

The aim of this study was to investigate the extraction behavior of As, Pb, and Zn from mine tailings for considering the feasibility of soil washing. Extraction of metals was studied for different extractant doses, solid/liquid ratios, and equilibrium times. Generally, high extraction efficiency was achieved with HCl, H(3)PO(4), and H(2)SO(4), while H(2)SO(4) proved to be problematic with respect to Pb. NaOH was found to be favorable in removing As, while it was not effective at extracting Pb and Zn. With optimum conditions, which were a 1:5 solid-liquid ratio and 2h of extraction time, 0.5M of HCl extracted 21.1-72.5%, 9.9-86.5%, and 6.1-74.1% of As, Pb, and Zn, respectively. The power and Elovich function were adequate to describe adsorption kinetics. These results suggest that HCl and NaOH could be used to effectively extract all metals without selectivity and As with selectivity, respectively, in mine tailings and could be used for the design of soil washing process.

The solubilization characteristics of DNAPLs by oil-based emulsion

Abstract: Because of its large surface area and hydrophobicity, a microsized oil emulsion can solubilize dense nonaqueous phase liquids (DNAPLs). When DNAPLs are solubilized by emulsion, they can be removed from the aquifer and their downward migration in the aquifer can be delayed or prevented due to the buoyancy force of the emulsion. Solubilization of DNAPLs was investigated in this study by using an oil-based emulsion prepared via mechanical homogenization of silicone oil. The emulsion droplets that were produced showed similar microsized distribution: the particles in the range of l-10p.m in diameter were 99% in number distribution and 80% in volume distribution. The oil-based emulsion effectively solubilized trichloroethylene (TCE) and 1,2-dichlorobenzene (DCB) as target pollutants. The emulsion prepared with 2% silicone oil that had been homogenized at 8000rpm for 15 min could solubilize 99.7% of 7800ppm DCB and 90.7% of 10,000 ppm TCE. Even the emulsion prepared with a low concentration (0.5%, v/v) of silicone oil removed 99.0% of 7800 ppm DCB from the aqueous phase. Taken together, the results of this study show the potential of the oil-based emulsion as an effective alternative to treat DNAPLs in the aquifer.

One-dimensional column and three-dimensional box flushing of silicone emulsion-enhanced remediation for chlorinated solvent contaminated soils

Aquifer contamination by dense non-aqueous phase liquids such as chlorinated solvents poses a huge threat to human health. Most chlorinated solvents biodegrade slowly under aerobic and anaerobic conditions. Furthermore, chlorinated solvents exist as free phase in aquifers and continuously contaminate groundwater because they have high density and low aqueous solubility. In this study, the feasibility of emulsion-based remediation for field application was investigated using a one-dimensional column and three-dimensional flushing. One-dimensional column experiments were performed to confirm the effects of soil components such as organics, silt, and clay on flushing performance. High organics (12%) and silt/clay (45%) inhibited solubilization of TCE. In three-dimensional flushing of TCE, a diagonal flow of emulsion was observed and downward migration of chlorinated solvents was prevented.

Removal of polycyclic aromatic hydrocarbons from contaminated soil in a two-phase partitioning bioreactor

A two-phase partitioning bioreactor was employed to remediate soil contaminated by a mixture of polycyclic aromatic hydrocarbons consisting of phenanthrene, anthracene, and pyrene. In this study, the transfer of three PAHs into the water-immiscible liquid phase (silicone oil or paraffine oil) from the soil was investigated during the first 24 h. And then, phenanthrene and anthracene were degraded by approximately 90% and 80%, respectively, compared with initial concentration in soil, but pyrene was not degraded during seven days of operation period. In addition, the feasibility of a soil slurry sequencing batch reactor system in terms of continuously operating a two-phase partitioning bioreactor was investigated. Phenanthrene and anthracene were degraded semi-continuously and repeatedly during two operating cycles. Pyrene was still not degraded and was just transferred into the water-immiscible liquid phase considering its solubility.

Options for reducing oil content of sludge from a petroleum wastewater treatment plant

Wastewater treatment plants at petroleum refineries often produce substantial quantities of sludge with relatively high concentrations of oil. Disposal of this waste is costly, in part because the high oil content requires use of secure disposal methods akin to handling of hazardous wastes. This article examines the properties of oily sludge and evaluates optional methods for reducing the oil content of this sludge to enable use of lower cost disposal methods. To reduce the oil content or break the structure of oily sludge, preliminary lab-scale experiments involving mechanical treatment, surfactant extraction, and oxidation are conducted. By applying surfactants, approximately 36% to 45% of oils are extracted from oily sludge. Of this, about 33% of oils are rapidly oxidised via radiation by an electron beam within 10 s of exposure. The Fenton reaction is effective for destruction of oily sludge. It is also found that 56% of oils were removed by reacting oily sludge with water containing ozone of 0.5 mg l-1 over a period of 24 h. Oxidation using ozone thus can also be effectively used as a pretreatment for oily sludge.

Application of Bioremediation to Soil Contaminated by Lubricants Around Railroad Turnouts

In this study, the feasibility of using bioremediation to treat lubricant-contaminated soil around railroad turnouts was investigated. Lubricants used during the maintenance of railroad turnouts can drip onto the ground causing soil contamination. In the laboratory experiments, the residual TPH (Total Petroleum Hydrocarbons) concentration in soil gradually decreased after microorganisms degrading the lubricants were added. Generally, the soil around railroad turnouts is covered by a layer of ballasts. In the column experiments that were designed considering field sites, the removal efficiency of TPH was about 11% after 60 days of cultivation time. In the field experiments, microorganisms were added into the soil periodically, and finally the residual TPH concentrations were reduced to less than 1,700 mg/kg-soil on average. These results indicate that the lubricant in the contaminated soil around railroad turnouts could be efficiently removed through bioremediation method.

Centrifugal polyelectrolyte enhanced ultrafiltration for removal of copper-citrate complexes from aqueous solutions

Abstract To replace the conventional dead‐end polyelectrolyte enhanced filtration (PEUF), which is a time consuming process in the optimization of process variables, centrifugal polyelectrolyte enhanced ultrafiltration was investigated to remove copper‐citrate complex in aqueous phase with a cationic polyelectrolyte, poly(diallydimethylammonium chloride) (PDADMAC). Effects of concentration ratios between polyelectrolyte, copper, and citrate and pH were observed. Below pH 3, copper was not removed by centrifugal PEUF. At the same concentration (1 mM) of citrate and copper, removal of copper at pH 5 was the highest value of 54%, 90%, and 98% with 5, 10, and 20 mM PDADMAC, respectively. Removal of copper decreased with the logarithmic ionic strength. Since the centrifugal PEUF is very economical in time compared with conventional dead‐end PEUF, the present method should be a valuable tool in the optimization of process variables.

Study of the Performance of a Dry Cleaning Method for Polluted Ballast Gravel of Railroad Fields

Ballast gravel in a railroad field is often polluted by grease and heavy metals. In this paper, the performances of a dry cleaning method for polluted ballast gravel in which pollutants on the gravel surface can be physically removed was extensively studied. A polluted ballast cleaning device able to shoot emery blasting media onto the surface using compressed air was prepared. Polluted ballast gravel was put into this device for cleaning, with the treatment time varied from 1 to 10 min. The cleaning efficiency of the total petroleum hydrocarbons and heavy metals were studied. The total petroleum hydrocarbon removal efficiency was 70-80% for gravels sampled from a locomotive waiting line, while it was 40-60% for gravels sampled from a turnout area. The heavy metal removal efficiency exceeded 90% for copper and lead, while it was 65-80% for nickel and zinc. This system was found to be effective for the remediation of polluted ballast gravels.

Effective CO2 Removal by Chlorella Sp. HA-1 in Various Cultivation Methods

Publisher Summary Biological CO 2 fixation using microalgal photosynthesis has many merits such as cheap initial cost and operation cost, no pre-treatment of flue-gas, and re-use of produced biomass. Most researches on the biological CO 2 fixation have focused on the enhancement of CO 2 fixation efficiency through the development of effective photobioreactors such as a con-shaped helical tubular photobioreactor, an internally illuminated photobioreactor, and an optical fiber reactor. However, there is a limitation in the improvement of the amount of CO 2 fixation by the development of photobioreactor. Another alternative is the improvement by the control of operation methods. These methods have certain drawbacks in the maintenance of CO 2 fixation rate. In biological CO 2 fixation, high growth rate and high cell density are necessary for effective CO 2 removal, but it is difficult to obtain both aspects simultaneously in the conventional cultivation methods. Various cultivation methods were employed—fed-batch, medium replacement, and semicontinuous cultivation method. The high cell density and the moderate growth rate were obtained by replacing old medium by new medium. For the semi-continuous method, the characteristics of microalgal growth by dilution ratio were studied. The amount of CO 2 fixation in the fed-batch cultivation method was less than that in the medium replacement cultivation method. Therefore, the semi-continuous cultivation was the most effective method to remove a large amount of CO 2 for practical purpose.