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동의어 포함

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Contents

ABSTRACT 17

1. Introduction 21

1.1. General Statement 21

1.2. Previous Works 25

1.3. Scope of the Study 28

2. Materials and experimental methods 31

2.1. Materials 31

2.1.1. Bentonite 31

2.1.2. Organic compounds 31

2.2. Experimental Methods 33

2.2.1. Synthesis and characteristics of organobentonites 33

2.2.2. Anions adsorption properties of organobentonites 36

2.2.3. Anions desorption properties of organobentonites 36

2.3. Analytical Methods 37

2.3.1. X-ray diffraction(XRD) analysis 37

2.3.2. X-ray fluorescence spectrometer(XRF) analysis 38

2.3.3. Fourier transform infrared(FTIR) analysis 38

2.3.4. Thermal analysis(DTA, TG) 38

2.3.5. Surface area and porous structure analysis 39

2.3.6. Scanning electron microscopy(SEM) analysis 39

2.3.7. Ion chromatography(IC) analysis 39

2.3.8. UV-VIS spectrophotometer analysis 40

3. Synthesis and characterization of organobentonites modified with various types of organic compounds 41

3.1. Introduction 41

3.2. Characterization of Bentonite 42

3.3. Characterization of Organobentonites 50

3.3.1. Properties of dispersion and flocculation 51

3.3.2. Chemical composition of organobentonites 54

3.3.3. X-ray diffraction analysis 60

3.3.4. FTIR analysis 75

3.3.5. Thermal analysis(DTA, TG) 81

3.3.6. Surface area and porous structure analysis 86

3.3.7. Scanning electron microscopy(SEM) analysis 90

3.3.8. pH analysis 90

3.4. Discussion 96

4. Anions absorption properties of organobentonites 103

4.1. Introduction 103

4.2. Experimental Materials and Methods 103

4.3. Anions Adsorption Properties of Organobentonites 104

4.3.1. Anions(NO3-, SO42-, PO43-) adsorption characteristics(이미지참조) 106

4.3.1.1. Effects on the types of organobentonites 106

4.3.1.2. Effects on exchanged amount 122

4.3.1.3. Effects on reaction times 122

4.3.2. X-ray diffraction analysis 128

4.3.3. FTIR analysis 138

4.3.4. pH analysis 148

4.4. Discussion 151

5. Anions desorption properties of organobentonites 155

5.1. Experimental Materials and Methods 155

5.2. Anions Desorption Properties of organobentonites 155

6. Conclusions 157

REFERENCES 161

요약 173

감사의 글 176

LIST OF TABLES

Table 1. Chemical formula and molecular weight of organic compounds 34

Table 2. Chemical compositions and structural formula of untreated bentonite 44

Table 3. Turbidity variation of the supernatant solution of untreated bentonite with time 53

Table 4. Turbidity variation of the supernatant solutions of various organobentonites modified with cationic organic compounds with time 55

Table 5. Turbidity variation of the supernatant solutions of organobentonites modified with nonionic organic compounds with time 57

Table 6. Turbidity variation of the supernatant solutions of organobentonites modified with anionic organic compounds with time 57

Table 7. Chemical compositions of untreated bentonite and organobentonites 59

Table 8. Basal spacings of untreated bentonite and organobentonites 65

Table 9. The weight loss of samples by calcinations 87

Table 10. Pore structure characteristics derived from conventional analysis of nitrogen isotherms 89

Table 11. pH values of organobentonite suspensions 93

Table 12. The adsorption amounts and efficiencies for untreated bentonite in various concentrations of solutions 107

Table 13. The adsorption amounts and efficiencies for SDS-, OPPE-, and POE (20) OE-bentonite in various concentrations of solutions 107

Table 14. The adsorption amounts and efficiencies for HDTMA-bentonite in various concentrations of solutions 110

Table 15. The adsorption amounts and efficiencies for CP-bentonite in various concentrations of solutions 110

Table 16. The adsorption amounts and efficiencies for organobentonites modified with cationic organic compounds in various concentrations of phosphate solutions 116

Table 17. The adsorption amounts and efficiencies for organobentonites modified with cationic organic compounds in various concentrations of nitrate solutions 117

Table 18. The adsorption amounts and efficiencies for organobentonites modified with cationic organic compounds in various concentrations of sulfate solutions 118

Table 19. The adsorption amounts and efficiencies for HDTMA- and CP-bentonites on 100% and 200% CEC equivalent amount exchanged condition 123

Table 20. The adsorption amounts and efficiencies for CP-bentonites (200% CEC equivalent amount exchanged) according to reaction times in 100 ㎎/L nitrate, sulfate, and phosphate solutions 126

Table 21. pH values of CP-bentonite suspensions after adsorption of different anions with reaction times 149

Table 22. pH values of organobentonite suspensions and adsorption efficiencies of various organobentonites after anion adsorption 150

LIST OF FIGURES

Figure 1. Various types of organic compounds used in manufacturing of organobentonites. 35

Figure 2. Nitrogen adsorption isotherms of untreated bentonite. 43

Figure 3. X-ray diffraction patterns of untreated bentonite 46

Figure 4. FTIR spectrum of untreated bentonite. 47

Figure 5. SEM images of untreated bentonite : magnification ×15000(a) and ×30000(b). 49

Figure 6. Dispersion and flocculation behaviors according to the type of organic compounds and exchanged CEC amounts. 52

Figure 7. Turbidity variation of the supernatant solutions of bentonite and organobentonites modified with cationic organic compounds such as TMA, CP and HDTMA (1T... 56

Figure 8. Turbidity variation of the supernatant solutions of bentonite and organobentonites modified with anionic and nonionic organic compounds (1T : 100% CEC, 2T : 200% CEC... 58

Figure 9. Alkylammonium expansion of expansible clay minerals (Lagaly and Weiss, 1969 ; Lagaly, 1982) 61

Figure 10. The stepwise increase of the basal spacing dL of alkylammonium smectites with the alkyl chain length (expressed by the number n of the carbon atoms in the alkyl chain)...(이미지참조) 62

Figure 11. Schematic representation of the effect of aliphatic chain length and mineral charge density on the adsorption of quaternary ammonium cations on... 63

Figure 12. X-ray diffraction patterns of organobenfonites modified with cationic organic compounds (alkyl-)(100% CEC equivalent amount exchanged) 66

Figure 13. X-ray diffraction patterns of organobentonites modified with cationic organic compounds (alkyl-)(200% CEC equivalent amount exchanged) 67

Figure 14. X-ray diffraction patterns of organobentonites modified with cationic organic compounds (benzyl- and pyridinium-) (100% CEC equivalent amount exchanged) 68

Figure 15. X-ray diffraction patterns of organobentonites modified with cationic organic compounds (benzyl- and pyridinium-) (200% CEC equivalent amount exchanged) 69

Figure 16. Variations in X-ray diffraction patterns of HDTMA-bentonite (200% CEC equivalent amount exchanged) with heating temperatures. 71

Figure 17. Variations in X-ray diffraction patterns of CP-bentonite (200% CEC equivalent amount exchanged) with heating temperatures. 72

Figure 18. X-ray diffraction patterns of organobentonites modified with anionic organic compounds. 73

Figure 19. X-ray diffraction patterns of organobentonites modified with nonionic organic compounds. 74

Figure 20. Basal spacing change of HDTMA-bentonite with the reaction times. 76

Figure 21. Basal spacing change of CP-bentonite with the reaction times. 77

Figure 22. Basal spacing change of OPPE-bentonite with the reaction times. 78

Figure 23. FTIR spectra of CP, CP-bentonite and untreated bentonite. 79

Figure 24. FTIR spectra of HDTMA, HDTMA-bentonite and untreated bentonite. 80

Figure 25. FTIR spectra of (A) SDS, (B) SDS-bentonite and (C) untreated bentonite. 82

Figure 26. DTA and TG curves of (A) untreated bentonite, (B) HDTMA-bentonite and (C) CP-bentonite. 83

Figure 27. Nitrogen adsorption isotherms of CP-bentonite, HDTMA-bentonite and untreated bentonite. 89

Figure 28. SEM images of (A) untreated bentonite (B) HDTMA-bentonite (C) CP-bentonite (D) SDS-bentonite (E) OPPE-bentonite (F) POE (20) OE-bentonite. Magnification ×15000 91

Figure 29. Variation in pH of organobentonite suspensions with reaction times. 94

Figure 30. Variation in pH of organobentonite suspensions with chain length, chain structure and exchanged CEC amount (A) alkyl- and (B) benzyl- and pyridinium-bentonites. 95

Figure 31. Variations in adsorption amount for (A) SDS-, (B) OPPE-, and (C) POE (20) OE-bentonite in various concentrations of solutions. 108

Figure 32. Variations in adsorption efficiency for (A) SDS-, (B) OPPE-, and (C) POE (20) OE-bentonite in various concentrations of solutions. 109

Figure 33. Variations in adsorption amount for (a) untreated-bentonite (b) HDTMA-bentonite, and (c) CP-bentonite in various concentrations of... 111

Figure 34. Variations in adsorption efficiency for (a) untreated-bentonite, (b) HDTMA-bentonite, and (c) CP-bentonite in various concentrations of... 112

Figure 35. Adsorption isotherms of nitrate, phosphate, and sulfate ions for (a) HDTMA-bentonite and (b) CP-bentonite. 114

Figure 36. Variations in adsorption amount for organobentonites modified with cationic organics compounds (alkyl-) in various concentrations of solutions (A) PO43-, (B)(이미지참조)... 119

Figure 37. Variations in adsorption efficiency for organobentonites modified with cationic organics compounds (alkyl-) in various concentrations of solutions (A) PO43-, (B)...(이미지참조) 120

Figure 38. Variations in adsorption amount and efficiency for organobentonites modified with cationic organic compounds (benzyl- and pyridinium-) in various... 121

Figure 39. Charts of adsorption amounts for HDTMA- and CP-bentonites according to exchanged CEC amounts in 100 mg/L of nitrate, sulfate, and... 124

Figure 40. Charts of adsorption efficiency for HDTMA- and CP-bentonites depending on exchanged CEC amounts in 100 mg/L of nitrate, sulfate, and phosphate solutions. 125

Figure 41. Variations in adsorption amount and efficiency for CP-bentonites (200% CEC equivalent amount exchanged) with reaction times at 100 mg/L... 127

Figure 42. X-ray diffraction patterns of untreated bentonite after adsorption of anions. 129

Figure 43. X-ray diffraction patterns of CP-bentonite after adsorption of anions (A) 100% CEC equivalent amount exchanged organobentonite (B)... 130

Figure 44. X-ray diffraction patterns of CP-bentonite after adsorption of anions in various concentrations. 132

Figure 45. X-ray diffraction patterns of HDTMA-bentonite after adsorption of anions (A) 100% CEC equivalent amount exchanged organobentonite (B)... 133

Figure 46. X-ray diffraction patterns of HDTMA-bentonite after adsorption of anions in various concentrations (A) nitrate, (B) sulfate, and (C) phosphate. 135

Figure 47. FTIR spectra of untreated bentonite after adsorption of anions. 139

Figure 48. FTIR spectra of CP- bentonite (100% CEC equivalent amount exchanged) after adsorption of anions. Arrows and circle indicated each anion peak. 140

Figure 49. FTIR spectra of CP- bentonite (200% CEC equivalent amount exchanged) after adsorption of anions. Arrow and circles indicate each anion peak. 141

Figure 50. FTIR spectra of CP- bentonite (200% CEC equivalent amount exchanged) after adsorption of various concentration of anions. Arrows indicate nitrate peak. 142

Figure 51. FTIR spectra of HDTMA- bentonite (100% CEC equivalent amount exchanged) after adsorption of anions. 143

Figure 52. FTIR spectra of HDTMA- bentonite (200% CEC equivalent amount exchanged) after adsorption of anions. Arrows indicate each anion peak. 144

Figure 53. FTIR spectra of HDTMA- bentonite (200% CEC equivalent amount exchanged) after adsorption of various concentrations of nitrate. Arrows indicate nitrate peak. 145

Figure 54. FTIR spectra of HDTMA- bentonite (200% CEC equivalent amount exchanged) after adsorption of various concentrations of sulfate. Arrows indicate sulfate peak. 146

Figure 55. FTIR spectra of HDTMA- bentonite (200% CEC equivalent amount exchanged) after adsorption of various concentrations of phosphate. Arrows indicate... 147

Figure 56. Variation in pH of CP-bentonite suspensions after adsorption of different anions with reaction times. 149

초록보기

다양한 종류의 유기화합물로 제조한 유기벤토나이트의 특성과 이것들의 음이온 흡착성에 대해 조사하였다. 유기벤토나이트의 특성은 X-선회절분석(XRD), X-선형광분석(XRF), 적외선분광분석(FTIR), 열분석(DTA, TG), 비표면적, 그리고 전자현미경분석(SEM)등을 이용하여 연구하였다.

다양한 유기화합물로 제조한 유기벤토나이트는 상온에서 저면간격이 14.2 - 25.9 Å(100% CEC 양으로 교환시킨 유기벤토나이트)와 14.2 - 42.0,4(200% CEC 양으로 교환시킨 유기벤토나이트)으로 현저한 층간팽창을 나타냈다. 이것은 유기화합물이 벤토나이트의 층간에 실질적으로 삽입되었음을 지시한다. 층간팽창의 정도는 유기화합물의 유형(분자량, 체인길이, 체인구조, 전하종류, 반응시간)과 반응시킨 CEC 양에 따라 다르다.

여러 종류의 유기화합물로 제조한 유기벤토나이트에 대하여 음이온의 흡착특성을 조사하였다. 흡착실험은 유기벤토나이트 시료 0.2g을 음이온인 질산이온, 황산이온, 인산이온의 각 여러 농도별 용액 40 ㎖와 반응시켜 행하였다 그 결과, 유기화합물의 종류에 따라 유기벤토나이트의 음이온 흡착거동은 다르게 나타났다. 양이온성 유기벤토나이트는 모든 음이온에 매우 높은 흡착능을 보이는 반면, 음이온성과 비이온성의 유기화합물로 제조한 유기벤토나이트는 무처리 벤토나이트와 같은 양상으로 음이온을 거의 흡착하지 않았다. 양이온성 유기벤토나이트의 흡착거동은 유기화합물의 구조(알킬기-, 벤질기-, 피리디늄-), 체인길이와 분자량에 따라 다르게 나타났다. 특히 양이온성유기화합물인 hexadecyltrimethylammonium(HDTMA)과 cetylpyridinium(CP)으로 제조한 HDTMA-벤토나이트와 CP-벤토나이트는 음이온들에 대해 높은 흡착률을 나타냈다. HDTMA-벤토나이트의 경우, 인산이온과 질산이온의 흡착률이 100 ㎎/L의 농도에서 약 90% 정도로 높게 나타나고, CP-벤토나이트의 경우, 질산이온의 흡착률이 100 ㎎/L의 농도에서 97%로 높게 나타났다. 이와 같이 음이온 및 유기벤토나이트의 종류에 따라 흡착거동이 약간 차이를 나타냈다. 질산이온과 인산이온의 흡착률은 황산이온에 비해 모두 상대적으로 높게 나타났다. 유기화합물을 CEC의 200% 양으로 교환시켜 제조한 HDTMA-와 CP-벤토나이트는 질산이온과 황산이온을 100% CEC 양으로 교환시켜 제조한 유기벤토나이트에 비해 2 배 이상의 높은 흡착률을 나타냈다. 반면에 인산이온은 반응시킨 CEC 양에는 상관없이 거의 유사하게 나타났다. 반응시간과 음이온의 종류에 따라서 CP-벤토나이트(200% CEC 양으로 교환시켜 제조한)의 음이온 흡착량이 다르게 나타났다. 즉, 질산이온은 CP-벤토나이트와 반응 즉시 흡착되는 반면에 황산이온과 인산이온은 시간이 경과함에 따라 서서히 흡착되었다.

CP-벤토나이트와 HDTMA-벤토나이트에 대한 음이온 탈착실험도 행하였다. 그 결과, 유기벤토나이트의 탈착정도는 pH에 관계없이 약 20% 정도로 나타났다. 흡착되었던 양을 고려하면, 탈착된 양은 유기벤토나이트의 표면에 약하게 붙어있었던 음이온에 의한 것이라 판단되며, 나머지 약 80%는 유기벤토나이트의 층간에 강하게 결합되어 있다고 볼 수 있다. 따라서 이러한 유기벤토나이트는 비교적 탈착에 안정하다고 생각된다.

유기벤토나이트의 특성에 대한 다른 여러 실험 및 분석 결과들은 특성의 근본원인과 흡착메커니즘을 해석하는데 유용한 자료로 제공되었다. 특히 이번연구의 결과는 유해성 음이온의 제거와 같은 환경오염처리에 활용될 수 있을 것으로 생각된다.