• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.53-60
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• 1997

A series of batch and lab-scale pilot tests were conducted to optimize the design parameters for the application of soil washing techniques to the soil contaminated by heavy metals. Cu, Pb, and Zn were selected as target heavy metals. The concentrations of Cu, Pb, and Zn were 500mg/kg dry soil, 1, 000mg/kg dry soil, and 500mg/kg dry soil, respectively. Citric acid and oxalic acid were used for the extractants. In the batch tests, the extraction efficiencies for Cu, Pb, and Zn were 79%, 72%, 72%, respectively. The proper extractant concentration and dilution ratio(weight/volume) for Cu and Pb were turned to be citric acid 50mM and 1:5, respectively. The extraction efficiencies were enhanced with the addition of 1~2% OA-5 or SDS. From pilot scale tests for Pb, first stage and second stage of soil washing resulted in the extraction efficiency of 59% and 78%, respectively.

• Journal of Soil and Groundwater Environment
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• v.10 no.6
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• pp.68-74
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• 2005

This study was carried out to evaluate the feasibility of field-scale sequential soil washing process for remediation on Kyongsangnamdo D mine soils which was heavily contaminated by arsonic. Arsenic concentration of untreated soils was $321\pm32mg/kg$. By applying the basic operating condition which was proposed from several pilot-scale experiments, arsenic concentration of treated soils was reduced 2.04 mg/kg ($99\%$ removal efficiency). We optimized the basic operating condition (mainly on washing solution concentration, cut-off size, and mixing ratio) to improve efficiently and economically the field-scale sequential soil washing process. The resulting optimized conditions were that solution concentration is 0.2M HCl, 1.0M HCl, 1.0M NaOH, that the cut-off size is 0.15mm (seive $\sharp$100), and that the mixing ratio is 1 3. Also, the optimized pH value for soil washing effluent treatment was 6 (33 ppb), in which the precipitation disruption caused by supersaturation of the floe did not occur. Results of TCLP tests showed that arsenic concentration from the washed gravels was 1.043 mg/L, that from soils ND (not detected), and that from filter cakes 0.066 mg/L. Also, the water content as a percentage of dewatered sludges was low $(48\%)$ and so the dewatered sludges can be disposed by landfilling. Through these results, we can concluded that tile field-scale sequential soil washing process developed in this study is adopted for remediation of arsenic-contaminated soils.

• Journal of Soil and Groundwater Environment
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• v.14 no.1
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• pp.78-82
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• 2009

In this study, the feasibility of soil washing and soil flushing was investigated to treat Zn-contaminated railroad soil. Various organic acids including ethylene diamine tetraacetic acid (EDTA) and citric acid as well as inorganic acids such as hydrochloric acid (HCl) and phosphoric acid were tested to evaluate washing efficiency. Generally, inorganic acid showed higher removal efficiency compared to organic acids. Particularly, EDTA, well known as the most effective washing agent for removal of heavy metals from soil, was not efficient to remove zinc in this study. Among washing agents tested in this study, HCl was the most effective. However, it is not effective to use HCl solution over 0.1 M concentration. Sequential process using HCl was effective to enhance the removal efficiency of zinc. In column test, the removal efficiency of Zn was 27%. Accordingly, it is feasible to treat Zn-contaminated railroad soil using soil washing or flushing with HCI.

• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.61-68
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• 2006

Soil washing techniques coupled with high pressure air jet were applied for diesel-contaminated soils sampled by an underground oil reservoir of which the initial total petroleum hydrocarbon (TPH) ($2,828{\pm}206\;mg/kg$) exceeded 5 times of current standard level (500 mg/kg) regulated by the Soil-Environment Conservation Law. Through several tests, we found that the position of impeller has a critical impact for washing efficiencies. The highest washing efficiency was obtained at an oblique angle (30 degree) for the impeller and optimized mixing speed (300 rpm) that could have high shearing forces. Considered economical and feasible aspects, the optimum mixing time was 10 min. Rate constants of TPH removal derived from the first-order equation were not linearly increased as mixing speed increased, indicating that mechanical mixing has some limits to enhance the washing efficiencies. Application of high-pressure air jet in washing process increased the washing efficiency. This increase might be caused by the fact that the surface of micro-air bubbles strongly attached hydrophobic matters of soil particles. As the pressure of air jet increased, the separation efficiencies of TPH-contaminated soil particles increased. In the combined process of high-pressure air jet and mixing by impeller, the optimum mixing speed and air flow-rate were determined to be 60 rpm and $2\;kg/cm^2$, respectively. Consequently, the washing technique coupled with high-pressure air jet could be considered as a feasible application for remediating petroleum-contaminated soils.

• Economic and Environmental Geology
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• v.52 no.1
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• pp.1-12
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• 2019

Batch experiments for the soil washing coupled with the magnetic separation process were performed to remediate the soil contaminated with metal and oil wastes. The soil was seriously contaminated by Zn and TPH (total petroleum hydrocarbon), of which concentrations were 1743.3 mg/kg and 3558.9 mg/kg, respectively, and initial concentrations of Zn, Pb, Cu, and TPH were higher than the 2nd SPWL (soil pollution warning limit: remediation goal). The soil washing with acidic solution was performed to remove heavy metals from the soil, but Pb and Zn concentration of the soil maintained higher than the 2nd SWPL even after the soil washing with acidic solution. The 2nd soil washing was repeated to increase the Pb and Zn removal efficiency and the Zn and Pb removal efficiencies additionally increased by only 8 % and 5 %, respectively, by the 2nd soil washing (> 2nd SPWL). The small particle separation from the soil was conducted to decrease the initial concentration of heavy metals and to increase the washing effectiveness before the soil washing and 4.1 % of the soil were separated as small particles (< 0.075 mm in diameter). The small particle separation lowered down Zn and Pb concentrations of soil to 1256.3 mg/kg (27.9 % decrease) and 325.8 mg/kg (56.3 % decrease). However, the Zn concentration of soil without small particles still was higher than the 2nd SPWL even after the soil washing, suggesting that the additional process is necessary to lower Zn concentration to below the 2nd SPWL after the treatment process. As an alternative process, the magnetic separation process was performed for the soil and 16.4 % of soil mass were removed, because the soil contamination was originated from unreasonable dumping of metal wastes. The Zn and Pb concentrations of soil were lowered down to 637.2 mg/kg (63.4 % decrease) and 139.6 mg/kg (81.5 % decrease) by the magnetic separation, which were much higher than the removal efficiency of the soil washing and the particle separation. The 1st soil washing after the magnetic separation lowered concentration of both TPH and heavy metals to below 2nd SPWL, suggesting that the soil washing conjugated with the magnetic separation can be applied for the heavy metal and TPH contaminated soil including high content of metal wastes.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.60-66
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• 2008

Laboratory soil washing experiments with HCl or EDTA were conducted to remediate lead-contaminated soil in a firing range. After lead bullets were removed by standard sieve #18 (1.0 mM), Pb concentrations were measured by EPA Method 3050B (9,443 mg/kg) and Korea Standard Test (4,803.5 mg/kg). The results of the batch test showed that the removal efficiency curve was logarithmic and approximately 90% of lead in soil was removed, when HCl was used. In case of EDTA, the removal efficiency increased proportionally to the concentration of EDTA, up to 98% lead removal with 0.1M EDTA. High mixing strength resulted in increase of removal efficiency and kinetics showed that the most lead was extracted in 10 min.

• Journal of Soil and Groundwater Environment
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• v.13 no.5
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• pp.81-87
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• 2008

In accompany with the transfer of US army bases, recent surveys reported serious contamination of soils by the release of petroleum from storage facilities and heavy metals accumulated in rifle-ranges. These problems have made an increased concerns of cleanup technology for contaminated soils. In this study, a full-scale soil washing process improved by multistage continuous desorption and agitational desorption techniques was examined for petroleum-contaminated soils obtained from three different remedial sites that contained 29.3, 16.6, and 7.8% of silt and clay, respectively. The initial concentrations of total petroleum hydrocarbon (TPH) were 5,183, 2,560, and 4,860 mg/kg for each soil. Pure water was applied to operate washing process, in which water used for washing process was recycled 100% for over 6 months. The results of full-scale washing tests showed that the TPH concentrations for soils (> 3.0 mm) were 50${\sim}$356 mg/kg (85.2${\sim}$98.2% removal rates), regardless of the contents of silt and clay from in A, B and C soil, when the soils were washed at 3.0 kg/$cm^2$ of injection pressure with the method of wet particle separation. Based on the initial TPH concentration, the TPH removal rates for each site were 85.2, 98.2 and 89.9%. For soils in the range of 3.0${\sim}$0.075 mm, the application of first-stage desorption technique as a physical method resulted 834, 1,110, and 1,460 mg/kg of TPH concentrations for each soil, also additional multi-stage continuous desorption reduced the TPH concentration to 330, 385, and 245 mg/kg that were equivalent to 92.4, 90.6, and 90.1% removal rates, respectively. The result of multi-stage continuous desorption for fine soil (0.075${\sim}$0.053 mm) were 791, 885, and 1,560 mg/kg, and additional agitation desorption showed 428, 440, and, 358 mg/kg of TPH concentrations. Compared with initial concentration, the removal rates were 92.0, 93.9 and 92.9%, respectively. These results implied we could apply strategic process of soil washing for varies types of contaminated soils to meet the regulatory limit of TPH.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1236-1241
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• 2007

The feasibility of soil washing was investigated in the laboratory to treat heavy metals-contaminated railway soil. Various organic acids including ethylene diamine tetraacetic acid (EDTA) and citric acid as well as inorganic acids such as hydrochloric acid (HCl) and phosphoric acid were tested to evaluate washing efficiency. Generally, inorganic acid showed higher removal efficiency compared to organic acids. Specially, EDTA, which are well known as most effective washing agent to remove heavy metals from soil, was not efficient to remove heavy metals in this study. Among washing agents tested in this study, HCl was most effective. The removal of Cd, Cu, and Pb was high, however, that for Zn and Ni was less than 30% with 0.5 M HCl. This difference comes from analytical methods (Korean Standard Test Method for Soil). Aqua regia was used to extract Zn and Ni, however 0.1 N HCl was used for other metals. As a result, simple washing technology is not effective, to treat railway contaminated soil with heavy metals.

• Proceedings of the KSEEG Conference
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• 2002.04a
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• pp.25-27
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• 2002

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.242-242
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• 2004

원자력발전소의 운전과정에서 계획적 혹은 비계획적으로 방출되는 미량의 입자상 방사성 물질들은 대부분 원전 부지내 토양에 침적되게 된다. 이러한 과정 속에서 오염토양이 발생하게 되면 수거되어 단순 격리관리하고 있는 실정이지만 앞으로 원전의 해체과정 등으로 인한 오염토양이 상당량 발생할 것으로 예상되기 때문에 적절한 제염을 통하여 폐기물량을 최소화시킬 필요가 있다. 이를 위해 오염토양 제염공정으로 물을 이용한 토양세척법을 선정하여 제염장치를 제작하였으며 실증시험을 수행하였다.(중략)