電化學整治方法是在現地整治相當有效的方法。其重要機制包括水之電解、重金屬離子之吸附/脫附，沉澱，水力流，電滲透流，及離子遷移等。本研究首先探討污染土壤中鉛、鎘離子之移除。土壤之pH值對重金屬離子之移除有重大之影響。除了吸附/脫附，沉澱和土壤之pH值有密切關係外，電滲透流之大小和方向，也受它的影響。因此土壤試體之pH值需調整至適當值。在水力梯度下，其適當值pH值約在2∼4之間。但在無水力梯度之情況下，pH值則宜在3∼6之間。為維持土壤試體之適當pH值分佈，因此運用了各種加強整治之方法。這些方法包括使用緩衝溶液、使用陽離子交換膜、及使用醋酸及醋酸鈉之緩衝液作前處理。這些加強整治方法在改善移除效率方面都證明是相當有效的。當使用緩衝液整治時，效果最好，Cd+2之移除率可達99%，而鉛可達85%。在無水力梯度下，其pH值之分佈、 電滲透係數對時間之變化、土壤殘餘重金屬之分佈和有水力梯度時其相對應之整治情況相當接近，唯移除率較低。
根據前面實驗之結果，進行模擬現場之整治，將陰極槽及陽極槽重新設計。整治之結果，銅離子之移除率可達63%，證明現地整治是可行的。並以理論方式，求得電極各種排列方式之電壓及電場強度分佈，以兩排圓形電極中間插入平板電極最佳，六角排列次之，平行排列、交錯排列無效面積最高。Electrochemical treatment is an emerging technology for decontaminating soil in-situ, which involves electrolysis, adsorption, desorption, precipitation, hydraulic or electroosmotic flow, and ionic transport. The removal of Pb and Cd ions from contaminated soils has been investigated in this study. The pH value of the soil significantly affects the removal of heavy metal ions. Besides the adsorption / desorption and precipitation are strongly affected by the pH of the soils, it can also influence the magnitude and direction of electroosmotic flow, and so the pH of the soil specimen must be regulated adequately. The appropriate range of pH values has been found to be 2〜4, and the pH must not exceed 6. Various enhancing methods of ensuring adequate pH distribution were employed herein, including methods that involve buffer solution, cation exchange membranes and pretreatment with acetic acid and acetate buffered solution. Such methods proved to be highly effective in improving the removal efficiency in all instances. The removal efficiency of Cd+2 can reach 99%, and that of Pb+2 can reach 85%, when buffered solutions are used for the electrochemical treatment. Remediation without hydraulic head is also investigated. The various results are similar with that of remediation with hydraulic head. Only the removal efficiency is less which is the impact of no hydraulic flow.
The bench scale tests are employed to examine the feasibility of in-situ remediation. The anode and cathode chambers are designed to facilitate the removal of contaminants from soil, the results prove to be satisfying. The removal efficiency of copper ions is 63%. That means the method we are developing is useful for in-situ remediation.
The effect of electrode configuration is also examined theoretically by voltage and electric field distribution. The array of a plate electrode between two rows of cylindrical electrodes is the best, then the hexagonal array, and then parallel type and cross type.目 錄
誌 謝 Ⅰ
中文摘要 Ⅱ
英文摘要 Ⅲ
目錄 Ⅳ
表目錄 Ⅶ
圖目錄 Ⅷ
第一章 緒 論 1
1-1 土壤污染 1
1- 2 台灣土地污染的現況 3
1- 3 土壤污染整治之各種方式 9
1- 4 土壤污染整治技術的選擇 15
1-5 台灣目前使用之整治方式 17
第二章 文 獻 回 顧 21
第三章 土 壤 之 性 質
3-1 土壤之成分與構造 29
3-2 土壤之性質 39
第四章 電化學處理污染土壤之原理及機制 47
4-1 離子遷移(Electromigration) 49
4-2 電泳(Electropherosis) 55
4-3 電滲透(Electroosmosis) 56
4-4 土壤中流體之流動 59
4-5 質量輸送 62
4-6 電荷通量(Charge Flux) 62
4-7 電遷移和電滲透之比較 67
4-8 水之電解(Electrolysis) 68
4-9 吸附及脫附 69
4-10 沉澱及溶解 78
第五章 實驗土壤特性之確認
5-1 粒徑分析 85
5-2 土壤pH值之測量 86
5-3 土壤含水量之測量 86
5-4 土壤孔隙度之測量 86
5-5 Zeta potential 的測量 86
5-6 滲透係數之測量 91
第六章 實驗設備與方法
6-1實驗設備 97
6-2實驗前之準備工作 101
6-3 分析方法 102
6-4實驗方法 104
第七章 實驗結果與討論
7-1 以純水及酸液沖洗土壤 109
7-2 以定電壓整治土壤 114
7-3 使用緩衝液協助整治土壤 128
7-4 使用陽離子交換膜 129
7-5 施加電壓整治前之前處理 136
7-6 只施加電壓而無水力梯度 144
7-7 結 論 159
第八章 一維之現場模擬整治
8-1 引 言 161
8-2 實驗裝置 161
8-3 實驗方法 163
8-4 實驗結果 165
8-5 結 論 180
第九章 電極之排列
9-1 前 言 181
9-2 各種電極排列之電壓及電場之分佈 181
9-3 各種電極排列之比較 194
第十章 結 論 196
符 號 說 明 199
參 考 文 獻 201
表目錄
Table 1- 1 臺灣地區土壤重金屬含量標準與等級區分表 4
Table 1- 2 台灣地區土壤重金屬含量等級意義說明 5
Table 1- 3 台灣地區土壤重金屬含量列為第五級地區與超過土壤
污染管制標準面積分布表 8
Table 1- 4 The vaporization temperatures of heavy metal from soil specimen 14
Table 1- 5 Tests performed by Geokinetics International, Inc.(Geokinetics) 18
Table 3- 1 Cation exchange capacity of common materials in soils (pH 7.0) 42
Table 4- 1 Diffusion coefficient, ionic mobility at infinite dilution and effective ionic mobility in soils with n=0.6 and τ=2.857 51
Table 4- 2 The solubility product Ksp of hydroxides, carbonates
and sulfates of OH-, CO3=, SO4= 80
Table 5- 1 Basic characteristics of the soil 88
Table 5- 2 the effect of pH on the value of and of kaolinite 95
Table 6- 1 Experimental conditions and removal efficiency (1) 105
Table 6- 2 Experimental conditions and removal efficiency (2) 106
Table 6- 3 Experimental conditions and removal efficiency (3) 107
Table 6- 4 Experimental conditions and removal efficiency (4) 108
Table 7- 1 the cation analysis (ppm) of the original soil specimen
and various position after 20 days’treatment 127
Table 7- 2 The extraction of heavy metals from soil specimen with acetic acid 139
Table 8- 1 Experimental conditions and removal efficiency 164
Table 9- 1 The ratio of ineffective area for various configuration of electrodes 194
圖目錄
Fig. 3-1 Silica tetrahedron 31
Fig. 3-2 Silica Tetrahedron Layer 31
Fig. 3-3 Schematic representation of Silica Tetrahedron Sheet 32
Fig.3-4 Octahedral Unit 32
Fig. 3-5 Octahedral Sheet 33
Fig. 3-6 Schematic representation for Gibbsite and Brusite 33
Fig. 3-7 The structure of kaolinite 37
Fig. 3-8 The structure of illite 37
Fig. 3-9 The structure of vermiculite 38
Fig. 3-10 The structure of montomorillonite 38
Fig. 3-11 Diagram of cation exchange 42
Fig. 3-12 The structure and surface potential distribution of EDL 46
Fig. 4-1 Schematic Mechanisms of Electrochemical Soil Remediation 48
Fig. 4-2 Concentration of NH4+ ion vs. time at various positions 53
Fig. 4-3 Concentration of SO4-2 ions vs. time at various positions 54
Fig. 4-4 Development of Electroosmotic flow 57
Fig. 4-5 Velocity profile of hydraulic flow and electroosmotic flow 57
Fig. 4-6 Zeta potential of kaolinite at various pH values 64
Fig. 4-7 The effect of ionic strength on the zeta potential of kaolinite
at various pH values 65
Fig. 4-8 The effect of Pb+2 ion on the zeta potential of kaolinite at various pH values (Ionic strength=0.02M) 66
Fig. 4-9 Percentage reduction of Pb+2 adsorbed on Illite
with the presence of each co-ion 72
Fig. 4-10 Adsorption of Cd+2, Cr+3, Cu+2, Ni+2, Pb+2, and Zn+2
from the cocktail solution at 30ｏC 73
Fig.4-11The adsorbed concentration of Pb versus the concentration
in the lead nitrate solution at pH = 4 74
Fig. 4-12 The adsorption concentration of Cd versus that in the cadmium chloride solution at pH = 6.0 75
Fig. 4-13 The adsorbed fraction of Pb versus pH of the solution 76
Fig. 4-14 The adsorbed fraction of Cd versus pH of the solution 77
Fig. 4-15 Various types of Pb at various pH values 81
Fig. 4-16 Various types of Cd at various pH values 82
Fig. 4-17 The effect of carbonate and sulfate ions on the solubility of Pb+2ion 83
Fig. 5-1 The accumulative size distribution of soil particles 89
Fig. 5-2 Zeta potential of soil sample at various pH values 90
Fig. 5-3 Schematic diagram of measuring apparatus of permeability 94
Fig. 5-4 The comparison between experimental and calculated values of ke 96
Fig. 6-1 Schematic diagram of experimental apparatus 98
Fig. 7-1 The accumulated effluent volume vs. time by pure water flushing 112
Fig. 7-2 Residual fractions of Pb &Cd vs. position by pure water and
0.05M nitric acid flushing 113
Fig. 7-3 The pH distribution across soil specimen after 20 days and 30days’treatment 115
Fig. 7-4 The accumulated volume of effluent vs. time with and without applying voltage 117
Fig. 7-5 The plot of average ke and kh vs. time 118
Fig. 7-6 Residual fraction vs. position under constant voltage (20 V / 20 cm) 121
Fig. 7-7 The distribution of water content at applied voltage (20V / 20 cm) 122
Fig. 7-8 The current variations with time at applied voltage (20V/ 20cm) 125
Fig. 7-9 The conductivity of cathode effluent vs. time at applied voltage 126
Fig. 7- 10 The pH distribution for treatment with Buffered Solution or cation exchange membrane (20V/ 20 cm, 20 days) 132
Fig.7-11 Residual fractions of Pb & Cd vs. position for buffered solution employed
at cathode (Test 5) 133
Fig. 7-12 The residual fraction of Pb & Cd vs. position in Test 6 & Test 7 134
Fig. 7-13 The residual fraction vs. position for the cases of Test 7 and Test 8 135
Fig. 7- 14 the pH distribution with the soil pretreated with acetic acid
and buffered solution (20 V/ 20 cm, 20 days) 140
Fig. 7-15 the comparisons of pH between test 8 and test 11 & between test 7 and test 12 141
Fig. 7-16 The metal residual distributions for the soils with pretreatment 142
Fig. 7-17 The metal residual distributions of test 11、test 12 143
Fig.7-18 The accumulated effluent without hydraulic head (Test 13) 146
Fig. 7-19 The accumulated effluent without hydraulic head (Test 14) 147
Fig.7-20 Ke value vs. time without hydraulic head (Test 14) 148
Fig.7-21 The pH distribution vs. position without hydraulic head 149
Fig.7-22 The voltage distribution vs. position at various times (Test 15) 152
Fig. 7-23 The plot of current vs. time (Test 13、Test 14) 153
Fig. 7-24 The plot of current vs. time (Test 15) 154
Fig. 7-25 Water content vs. position (Test 14、Test 15) 155
Fig.7-26 The residual fraction of Pb & Cd vs. position (Test 13，Test 14，Test 15) 158
Fig. 8-1 Schematic diagram of experimental Apparatus 162
Fig. 8-2 the plot of current vs. Time of Test 8-1、Test 8-2、Test 8-3 167
Fig. 8-3 pH distribution vs. position (Test 8-1) 168
Fig. 8-4 pH distribution vs. position (Test 8-2) 169
Fig. 8-5 pH distribution vs. position (Test 8-3) 170
Fig. 8-6 Voltage distributions vs. position (Test 8-1) 173
Fig. 8-7 Voltage distributions vs. position (Test 8-2) 174
Fig. 8-8 Voltage distributions vs. position (Test 8-3) 175
Fig. 8-9 The plot of accumulated effluent volume vs. time 176
Fig. 8-10 Residual concentration vs. position (Test 8-1) 177
Fig. 8-11 Residual concentration vs. position (Test 8-2) 178
Fig. 8-12 Residual concentration vs. position (Test 8-3) 179
Fig. 9-1 Schematic diagram of hexagonal and parallel arrays 184
Fig. 9-2 Schematic diagram of cross array and a plate electrode between
two rows of electrodes 185
Fig. 9-3 The voltage distribution of hexagonal array 186
Fig. 9-4 The electric field distribution of hexagonal array 187
Fig. 9-5 The voltage distribution of parallel array 188
Fig. 9-6 The electric field distribution of parallel array 189
Fig. 9-7 The voltage distribution of cross array 190
Fig. 9-8 The electric field distribution of cross array 191
Fig. 9-9 The voltage distribution of the array with a plate electrode between
two rows of electrodes 192
Fig. 9-10 The electric field distribution of the array with a plate electrode between
two rows of electrodes 19
