초록 ▼

개발 목적 및 필요성
토양세척법은 토양입자에 결합되어 있는 오염물질을 액상으로 추출하여 토양입자로부터 분리해 제거하는 기술로 주로 중금속과 유기오염물질의 처리에 활용된다. 하지만 국내 중금속 오염토양의 정화에 사용되는 토양세척공정은 무기산 위주의 획일적인 세척제 사용, 산세척으로 인한 토양질 저하 및 토양구조의 파괴, 많은 약품비용, 미세토양에서의 세척 효율 저하, 중금속 존재형태를 고려하지 않는 획일적 처리, 중금속과 토양의 결합/반응에 대한 광물학적 특성 고려 부족과 같은 문제점을 안고 있다. 따라서, 앞에서 지적한 토양

개발 목적 및 필요성
토양세척법은 토양입자에 결합되어 있는 오염물질을 액상으로 추출하여 토양입자로부터 분리해 제거하는 기술로 주로 중금속과 유기오염물질의 처리에 활용된다. 하지만 국내 중금속 오염토양의 정화에 사용되는 토양세척공정은 무기산 위주의 획일적인 세척제 사용, 산세척으로 인한 토양질 저하 및 토양구조의 파괴, 많은 약품비용, 미세토양에서의 세척 효율 저하, 중금속 존재형태를 고려하지 않는 획일적 처리, 중금속과 토양의 결합/반응에 대한 광물학적 특성 고려 부족과 같은 문제점을 안고 있다. 따라서, 앞에서 지적한 토양 세척법의 문제점을 해결하기 위하여 토양과 중금속의 특성 및 토양과 중금속간의 결합형태를 분석하여 토양세척공정의 질적 향상을 도모하고, 최종적으로 성공적인 환경친화적 세척프로토콜을 제안하고자 한다.

연구개발 결과
1차년도에서는 제련소부지 토양 내 비결정질 철/알루미늄 산화물 혹은 결정질 철/알루미늄 산화물과 결합한 비소를 제거하는데 있어 oxalic acid의 타당성을 평가하였다. 특히, 비결정질 철/알루미늄 산화물과 결합하고 있는 비소는 oxalic acid을 사용함으로서, 철을 추출함과 동시에 비소를 함께 추출하여 토양환경우려기준치인 25 mg/kg을 만족할 수 있었다. 또한, 결정질 철/알루미늄 산화물에 결합된 광미 내 비소의 경우, scorodite, orpiment은 oxalic acid가 환원제 및 킬레이트작용을 함께 하게 되어 비소의 추출에 있어 효과적인 것을 확인할 수 있었다. 세척공정 적용 후 토양질 평가를 위하여 비소와 pH에 민감한 해바라기씨의 발아율 평가에서 염산과 대비해 약 33%의 증가를 확인하였다.

2차년도에는 용산 폐기물 매립부지의 토양 내 exchangeable 및 Fe-Mn oxides fraction으로 존재하는 구리 및 납의 제거에 있어 EDTA 및 oxalic acid을 반복적으로 사용하였을 때, 잔류토양의 구리 및 납의 농도가 토양환경보전법 1지역 우려기준치 미만으로 감소하는 것을 확인할 수 있었다. 구리의 경우, oxalic acid을 사용함으로 인해 Fe-Mn oxides fraction으로 존재하는 상당부분이 용액 중으로 추출되었으며, 반대로 납은 oxalate와의 결합으로 인한 침전 때문에 효과적이지 않았다. 따라서, exchangeable fraction에 존재하는 부분 및 oxalic acid에 의해 추출된 구리와 납을 EDTA를 사용하여 chelating을 통해 구리와 납 모두 효과적으로 추출할 수 있었다. 반대로, 염산을 반복하여 사용할 경우, 정화기준치를 만족하지 못할 뿐만 아니라 토양이 산성화되었다. 또한, 용산 폐기물 매립부지의 토양 내 구리 및 납의 제거에 있어 EDTA와 oxalic acid을 반복 사용하여 세척공정을 적용한 후 처리토양에서의 wheat을 대상으로 한 발아시험에서 염산을 반복적으로 사용한 실험과 비교하여 40% 이상의 발아율 증가를 보였다.

3차년도에는 토양 내 ZnS의 형태로 오염된 부지의 정화를 위한 3가철을 이용한 토양세척공정을 적용하였을 때, 3가철이 2가철로 환원되면서 ZnS에 포함된 sulfide을 elemental sulfur으로 산화시켜 아연을 액상으로 추출할 수 있었으며, 염산과 비교하여 더 낮은 농도의 3가철을 사용함에도 불구하고 뛰어난 아연 추출효율을 보였다. 하지만, 오염토양 내 아연의 농도는 약 160,000mg/kg으로, 이를 처리하여 국내 정화수준으로 맞추는 것을 불가능하다고 판단하였으며 오염토양을 청토(淸土)와 섞어 아연의 농도를 실제 오염수준인 약 1,000 mg/kg으로 낮추어 세척실험을 진행하였다. 그 결과, 20 mM의 FeCl₃을 사용한 실험군에서 세척실험 후 토양 내 아연의 농도를 약 290 mg/kg까지 감소시켜 토양환경보전법 1지역 우려기준치를 만족할 수 있었으며, 100 mM의 염산은 460 mg/kg까지 감소시킬 수 있었다. 또한, 완두콩, 수수, 토마토,해바라기, 상추를 이용한 실험실 규모의 발아율 테스트 결과, FeCl₃을 사용한 실험군에서 세척 후 위 식물들은 염산 대비 각각 78%, 22%, 74%, 63%, 67%의 발아율 증가를 보였다.

성능사양 및 기술개발 수준
비소, 구리, 납과 아연을 대상으로 토양에서의 결합형태와 광물학적 특성을 규명하였으며, 이를 세척공정의 설계에 활용하였다. 이를 통해 처리 대상 중금속을 법적인 기준치 이내로 처리할 수 있었으며, 처리된 토양의 작물 발아율 실험을 통해 기존의 무기산보다 발아율이 향상된 것을 확인하였다.

활용계획
후속 실용화 연구와 연계하여 본 원천기술개발을 통해 확보된 기술을 실용화 할 것이며, 이를 산업체에 기술이전하여 실제로 활용되도록 할 계획이다.

( 출처: 요약서 3p )

Abstract ▼

Ⅳ. Results
1. The 1^st years
In this research, the characteristics of Arsenic-contaminated soil were evaluated by fractionation in soils from three types of high-level contaminated soils with As in the former smelting and mining area. Arsenic in sample 1 and 2 collected from smelting

Ⅳ. Results
1. The 1^st years
In this research, the characteristics of Arsenic-contaminated soil were evaluated by fractionation in soils from three types of high-level contaminated soils with As in the former smelting and mining area. Arsenic in sample 1 and 2 collected from smelting sites was observed to bind crystalline Fe oxides and/or present orpiment(As₂S₃) form and amorphous Fe oxides, respectively. In sample 3 collected from mining site, As was formed to scorodite(FeAsO₄·2H₂O) and orpiment and bound to pyrite(FeS₂) and jarosite(KFe³⁺₃(OH)₆(SO₄)₂) in soil. The fractionation and/or mineralogical form of As in soil influenced bioavailability of As, and bio-accessibility of As was decreased in amorphous Fe oxides(sample 2), crystalline Fe oxides(sample 1), and scorodite/orpiment form(sample 3) order. In this research, soil washing process using inorganic acids, oxalic acid, NaOH, and EDTA was carried out to remove As from contaminated soils. Washing results showed that As bound to amorphous Fe oxides was more extracted than that of bound to crystalline Fe oxides and/or sulfides from soils. These indicate that the extraction of As from soil was highly influenced by the fractionation and/or mineralogical form of As in soil. Among washing agents, oxalic acid was the most effective to extract As from soil because oxalate included in solution could function as chelating and/or reducing agent for amorphous Fe oxides from soil (sample 2). In particular, washing process using 50 mM of sodium oxalate at a solid-liquid ratio of 1:10 for 4 hour could remove As from sample 2 soil and meet Korea soil regulation level (25 mg As/kg soil). The ferrous iron extracted by sodium oxalate in acidic condition could be formed ferrous-oxalate complex which functioned as strong reducing agent. In addition, lab scale of seed germination tests using wheat(Triticum aestivum L.) and sun flower(Helianthus annus L.) were carried out to evaluate soil quality after washing process using oxalate and compare that with HCl. In overall result of seed germination tests, the washing process based oxalate could more enhance the seed germination rate approximately 33% than that of HCl. However, the solution including oxalate was not effective to extract As bound to crystalline Fe oxides and/or sulfides which could be extracted by dithionite of reducing agent and EDTA or citric acid of chelating agent (sample 1 and 3). The extraction of As was influenced solution pH as well as amount of washing agents.

2. The 2^nd years
The aim of this research was to develop eco-friendly and effective soil washing process instead of using conventional inorganic acid based on considering fractionation and mineralogy of soil and heavy metal from Pb- and Cu-contaminated soil formed by waste landfill.

Firstly, the extraction characteristics of Cu from model soil synthesized by silica and humic acid was evaluated to extract Cu combined with organic matter in soil. Oxidation process using H₂O₂ was not effective to destroy Cu-humic complexes in synthesized model soil as well as field soil because humic is made in oxidized condition of natural state usually. Also, H₂O₂ could not enhance extract Cu from the model soil deficient in some initiator or catalyst such as ferrous iron which are required for activation of H₂O₂ to produce OH radical. On the other hand, NaOH could effectively extract Cu as well as humic from synthesized model soil. However, both H₂O₂ and NaOH could not extract Cu and humic from field soil and change fractionation of Cu in soil. EDTA and citric acid could effectively extract Cu bound to organic matter via chelating reaction with humic from both model and field soil. In particular, EDTA adsorbed solid surface after washing might lead to secondary pollution to soil and groundwater.

Secondly, the applicability of washing process using ferric iron such as FeCl₃ and Fe(NO₃)₃ instead of conventional inorganic acids including HCl, HNO₃, and H₂SO₄ from artificial Pb-contaminated kaolinite was evaluated to compare extraction of Pb from soil.
Ferric iron produces hydrogen ion and Fe(OH)₃ via dissociation of water molecules where produced hydrogen ion could extract Pb adsorbed onto soil surfaces. The extraction of Pb from contaminated kaolinite was highly influenced by final as well as initial solution pH regardless of washing agents. This means that the removal mechanism of Pb from soil surface is ion exchange between hydrogen ion and Pb and chloride ion could slightly enhance extraction of Pb with Pb-Cl complexations. In case of ferric iron, the extraction of Pb from soil was much higher than that of HCl and HNO₃ because ferric iron remained in solution after washing could re-produce hydrogen ion by equilibrium reaction between ferric irons and hydrogen ions in solution which can extract Pb from soil repeatedly. On the contrary, H₂SO₄ was not effective to extract Pb from soil because Pb extracted into solution by ion exchange with hydrogen ions could be precipitated to anglesite(PbSO₄) with sulfate ions in acidic condition. In addition, ferric iron could more extract Pb bound to exchangeable fraction from field Pb-contaminated soil than that of HCl. Furthermore, ferric iron could more inhibit the extraction of soil components by Fe(OH)₃ than that of HCl.

Ferric iron can be the role of the extracting and/or oxidizing agent for dissolution various oxidized and reduced Pb minerals such as PbO, PbCO₃, Pb₃(CO₃)₂(OH)₂, PbSO₄, PbS, and Pb₅(PO₄)₃(OH) formed in field Pb-contaminated soil. The dissolution of these Pb minerals is influenced by solubility of each mineral. In this research, the extraction of Pb from various Pb minerals in soil washing process using ferric iron was compared with usual washing agents including HCl, HNO₃, EDTA, and citric acid. Among Pb minerals, PbS can be oxidized to soluble secondary Pb minerals in oxidizing environment naturally.
Ferric iron could effectively dissolve Pb minerals regardless of those solubility via extraction of soluble Pb minerals by hydrogen ions and oxidation of insoluble PbS by redox reaction between ferric and sulfide(S^2-). However, the extraction of Pb using FeCl₃ was lower than that of Fe(NO₃)₃ because chloride ions in solution by dissociation of water molecules could be combined with Pb extracted into solution, which was precipitated to cotunnite(PbCl₂) in solution after washing. Cotunnite has a high solubility for acidic solution and could be completely dissolved by second washing using deionized water because the residual soil pH was maintained to acidic condition by hydrogen ions via first washing using ferric iron. However, Fe(NO₃)₃ more extracted Pb from Pb minerals than that of FeCl₃ because nitrate included Fe(NO₃)₃ is an inert anion. Pb in field Pb-contaminated shooting range soil was mainly formed to hydrocerussite(Pb₃(CO₃)₂(OH)₂) and cerussite(PbCO₃) which was observed to exchangeable fraction in soil because of those high solubility. In overall washing results, EDTA and Fe(NO₃)₃ was the most effective to extract Pb from soil than that of HCl, HNO₃, and citric acid. Especially, EDTA could enhance the extraction of Pb via Pb-EDTA complexations with those strong combining strength.

Finally, soil washing process was carried out to remediate Cu- and Pb-contaminated field soil formed waste landfill site. Cu and Pb was mainly bound to Fe oxides in soil, EDTA and oxalic acid were used to extract them in this study. Oxalic acid was effective to extract Cu from soil via reducing of iron as well as complexing of Fe-oxalate.
However, oxalate could be precipitated to Pb-oxalate which was stable. On the contrary,EDTA was suitable to extract Fe as well as Pb via Pb- and Fe-EDTA complexations with a strong combining strength of them. The concentration of Cu and Pb in residual soil after a single washing process using oxalate or EDTA could not meet Korean soil quality level of both Cu and Pb. Four-step washing process using EDTA-EDTA-oxalic acid-oxalic could decrease the concentration of both Cu and Pb below the soil quality level. Furthermore, the result of seed germination test using wheat(Triticum aestivum L.) showed that four-step washing process using EDTA-EDTA-oxalic acid-oxalic acid could more enhance seed germination approximately 40% than that of HCl-HCl-HCl-HCl washing.

3. The 3^rd years
In this research, soil washing process using ferric iron was carried out to determine the dissolution characteristics of Zn minerals such as ZnO, (ZnCO₃)₂·(Zn(OH)₂)₃, ZnFe₂O₄, and Zns from artificially contaminated kaolinite with these Zn minerals. The washing results showed that a higher extraction efficiency of Zn from ZnO and (ZnCO₃)₂·(Zn(OH)₂)₃ which has is a soluble. However, the extraction of Zn from ZnFe₂O₄ by ferric iron was lower although has a high solubility because the dissolution of that is influenced by activity of iron. Ferric iron could extract Zn from ZnS via oxidation of sulfide to elemental sulfur(S⁰) and reduction of ferric to ferrous iron. Therefore, a 1:2 of molar ratio between ZnS and ferric is needed to extract Zn from ZnS. In addition, elemental sulfur oxidized from sulfide was oxidized to sulfate(SO₄^2-) finally. Based on these dissolution characteristics of ZnS, soil washing process using ferric iron was designed to remediate Zn-contaminated field soil formed by transportation of Zn minerals and compared with HCl. The concentration of Zn, Cu, Pb, and Cd in field soil was 160,000, 1,600, 4,700, and 660 mg/kg respectively which far exceeded Korean soil quality level. Most Zn was observed to ZnS form in soil. In contrast with previous washing result, washing results using ferric iron showed that approximately 20 % of Zn was extracted from soil for 24 hours because Zn might be competed with other heavy metals as well as cations in field soil.
Furthermore, multi-step washing process using ferric iron was not effective to extract Zn from soil too. This probably means that Zn in soil existed as form combined with soil minerals by weathering and/or aging of field soil, which would be different with Zn mineral ore in preliminary washing test. In results of seed germination tests using pea(Pisum sativum), sorghum(Sorghum bicolor), tomato(Solanum lycopersicum), sunflower(Helianthus annuus), and lettuce(Lactuca sativa) after washing process using 20 mM FeCl₃ and 100 mM HCl, the soil pH and cations in treated soil used FeCl₃ was higher than that of HCl. Furthermore, FeCl₃ could more effective to remove Zn from soil than HCl although the amount of FeCl₃ was lower than that of HCl. As a results, the washing process using FeCl₃ could more enhance seed germination rates of pea, sorghum, tomato, sunflower, and lettuce of 78%, 22%, 74%, 66%, and 67% respectively, than that of HCl.

( 출처 : SUMMARY 15p )

목차 Contents

• 표지 ... 1
• 제 출 문 ... 2
• 요 약 서 ... 3
• 요 약 문 ... 6
• SUMMARY ... 14
• 목차 ... 21
• 1. 연구개발의 필요성 및 동향 ... 23
• 1-1. 연구개발의 중요성(필요성) ... 23
• 1-2. 연구개발의 목표 ... 29
• 1-3. 연구개발 방법 ... 29
• 1-4. 연구개발대상 기술의 차별성 ... 29
• 2. 국내외 기술개발 현황 ... 31
• 2-1. 해외 기술개발 동향 ... 31
• 2-2. 국내 기술개발 동향 ... 33
• 3. 연구수행 내용 및 결과 ... 35
• 3-1. 연구개발의 추진전략·체계 및 연구수행 방법 ... 35
• 3-2. 연구개발의 내용(범위) 및 최종목표 ... 37
• 3-3. 연구개발 결과 요약 ... 138
• 4. 목표달성도 및 관련분야 기여도 ... 150
• 4-1. 목표달성도 ... 150
• 4-2. 관련분야 기여도 ... 153
• 5. 연구결과의 활용계획 ... 154
• 5-1. 추가연구의 필요성 ... 154
• 6. 연구과정에서 수집한 해외과학기술정보 ... 156
• 7. 연구개발결과의 보안등급 ... 158
• 8. 국가과학기술종합정보시스템(NTIS)에 등록한 연구시설·장비 현황 ... 159
• 9. 연구개발과제 수행에 따른 연구실 등의 안전조치 이행실적 ... 160
• 10. 연구개발과제의 대표적 연구실적 ... 161
• 11. 기타사항 ... 162
• 12. 참고문헌 ... 163
• 끝페이지 ... 171