Characteristics of Wettability Variation of Oil-Contaminated Porous Medium
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摘要: 一定程度的石油污染可使多孔介质的湿润性发生变异,导致介质持水能力降低、地下水石油污染、粮食产量品质下降等.采用滴水穿透时间法与酒精溶液入渗法,测定了亚粘土和粗砂在不同柴油、机油含量下的斥水水平,确定了亚粘土、粗砂由亲水表面变为疏水表面的临界含油量.结果表明,亚粘土、粗砂湿润性变异的临界机油含量分别约为7%、0.5%,粗砂湿润性变异的临界柴油含量约为14%,而柴油污染对亚粘土湿润性的影响不显著.另外,当石油污染多孔介质的含水量达到某一临界值时,湿润性将再次发生反转,由疏水表面变回亲水表面.测得机油、柴油污染粗砂的临界含水量约在0.2%~1%之间,机油污染亚粘土的临界含水量在数值上与其含油量近似相等.Abstract: A certain degree of oil pollution can lead to wettability variation in porous medium, which can bring about low water-holding capacity, oil contamination of groundwater, low food quality and production. In this study, water repellency of sand and clay was measured by WDPT and MED methods under different diesel and engine oil contents. Critical oil content of porous media in oil-contaminated porous media was determined preliminarily, beyond which hydrophilic surface could change into hydrophobic surface. The results show that critical oil contents of clay and sand contaminated by engine oil are about 7% and 0.5% respectively. Critical oil content of sand contaminated by diesel is about 14%, while diesel doesn't have remarkable effect on water repellency. In addition, when water content increases to a critical value, wettability of oil-contaminated porous medium will reverse again. Critical water contents of sand contaminated by engine oil and diesel are both between 0.2%-1%, while critical water content of clay contaminated by engine oil is approximately equal to its oil content in value.
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表 1 供试多孔介质的粒径分布与物理性质
Table 1. Grain size distribution and physical properties for porous media samples
多孔介质 比重 比表面积(m2·g-1) 各粒组含量(%) 工程分类 2~1 (mm) 1~0.5 (mm) 0.5~0.25 (mm) 0.25~0.1 (mm) 0.1~0.075 (mm) 0.075~0.005 (mm) 砂性土 2.66 4.69 17.4 45.3 27.9 8.1 0.3 1.0 粗砂 粘性土 2.70 31.57 0.6 0.3 0.2 0.7 75.6 22.6 粉质亚粘土 表 2 供试油品的基本性质
Table 2. Basic properties of diesel and engine oil
油品名称 密度(g·cm-3) 粘滞系数(mPa·s) 表面张力(mN·m-1) 油-水界面张力(mN·m-1) 0#柴油 0.848 3.56~4.05 27.8 19.0 CD15W-40机油 0.878 404~444 31.2 24.5 表 3 酒精溶液入渗法的斥水性描述与水平标准
Table 3. Water repellency description and level standard of MED method
水平 斥水性描述 酒精溶液体积分数(%) 7 极端斥水 36 6 异常强烈斥水 24 5 强烈斥水 13 4 中度斥水 8.5 3 轻微斥水 5 2 亲水 3 1 异常亲水 0 表 4 不同机油含量下亚粘土的MED入渗时间
Table 4. Infiltration time in clay by MED method in the condition of different engine oil contents
多孔介质含油率 不同体积分数的酒精溶液的入渗时间(s) 0 3% 5% 8.5% 13% 24% 36% 4% 1.82 1.63 1.31 1.12 0.95 0.66 0.52 6% 2.75 2.52 2.35 2.05 1.82 1.45 1.15 7% 4.51 4.34 4.03 3.65 3.12 2.41 2.14 7.25% 6.32 6.46 6.33 6.16 5.05 4.44 2.33 7.5% 6.54 6.74 7.45 6.82 6.75 4.81 2.43 8% 7.87 8.63 8.12 7.51 7.24 5.73 2.72 10% 34.21 27.61 25.23 17.52 17.53 11.23 3.44 表 5 不同机油含量下粗砂的MED入渗时间
Table 5. Infiltration time in sand by MED method in the condition of different engine oil contents
多孔介质含油率 不同体积分数的酒精溶液的入渗时间(s) 0 3% 5% 8.5% 13% 24% 36% 0.5% 4.11 3.92 3.65 3.15 2.51 1.82 1.45 0.8% 13.54 13.13 12.82 12.52 11.11 4.33 4.33 1% 30.55 30.23 28.15 23.13 20.92 4.92 1.62 2% 40.13 37.22 33.92 30.62 24.11 5.12 1.81 4% 50.14 42.65 31.32 30.12 26.34 5.74 2.14 表 6 不同柴油含量下粗砂的MED入渗时间
Table 6. Infiltration time in sand by MED method in the condition of different diesel oil contents
多孔介质含油率 不同体积分数的酒精溶液的入渗时间(s) 0 3% 5% 8.5% 13% 24% 36% 14% 4.82 4.64 4.13 3.82 3.15 2.67 2.15 16% 9.15 8.22 7.12 5.26 4.71 3.21 1.92 18% 14.15 13.81 13.34 12.91 5.34 4.33 2.18 -
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