离子强度对胶体及As（Ⅲ）在饱和多孔介质中运移的影响

发布时间：2018-05-18 11:24

本文选题：胶体吸附 + 胶体再运移　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：地下环境中存在大量胶体,可吸附污染物并促进污染物在土壤和地下水中运移,而有些胶体本身就是污染物,这些污染物进入水体后会对人类身体健康造成危害。近年来,胶体在土壤和地下水中的运移研究成为热点,研究表明地下环境的变化会引起土壤胶体的释放和沉积,研究地下水中土壤胶体的沉积和再运移对包气带和含水层中污染物的运移和修复有着重要的意义。本工作选用直径为1μm的聚苯乙烯乳胶微球为模拟胶体颗粒,石英砂为多孔介质,采用室内土柱实验研究了饱和稳定流中离子强度对胶体吸附和再运移的影响,并研究了水铁矿胶体与离子强度对重金属As~(3+)运移的影响。根据实验中所获取的浓度穿透曲线计算胶体吸附率(attachment coefficient)、再运移率(remobilization coefficient),根据DLVO理论绘制势能图,定量分析实验结果。实验结果表明,(1)随着溶液离子强度增加,胶体在多孔介质表面的吸附量增加。溶液离子强度为50 mM、60 mM、70 mM时,滞留在砂柱中的胶体量占总注入量的百分比分别是92.96%、94.62%、94.78%。(2)溶液离子强度的瞬间改变,可引起胶体的再运移。溶液离子强度改变相同,从50 mM降到10 mM时胶体再运移量最大,再运移率为3.88%;初始离子强度同为60 mM,离子强度下降至10 mM时胶体再运移量最大,再运移率为1.75%;背景溶液从电解质溶液直接转换为超纯水时的胶体再运移量比先转换为低浓度电解质溶液再转换为超纯水时大。表明胶体在饱和多孔介质中运移不仅受离子强度大小的影响,还与离子强度变化率和溶液化学历史条件有关。(3)砂柱中存在水铁矿胶体且不发生运移时,水铁矿胶体可吸附As~(3+)而抑制As~(3+)在饱和砂柱中的运移,且吸附量随离子强度的增加而增加。(4)水铁矿胶体在砂柱中分布较分散时,As~(3+)因吸附点位增多、与胶体接触时间增长而在砂柱中的滞留量比水铁矿胶体在砂柱顶端集中分布时大,表明胶体对As~(3+)在饱和多孔介质中运移的影响大于离子强度的影响。以上研究结果可为制定水土健康标准,预防和控制地下水受到病原性微生物等有机胶体以及胶体颗粒所携带的各种有机、无机污染物的污染提供理论基础和决策依据。
[Abstract]:There are a large number of colloids in the underground environment which can adsorb pollutants and promote the transport of pollutants in soil and groundwater. Some colloids themselves are pollutants which will cause harm to human health when they enter the water body. In recent years, the study of colloid migration in soil and groundwater has become a hot topic, and it has been shown that the change of underground environment will lead to the release and deposition of soil colloid. It is of great significance to study the deposition and remigration of soil colloids in groundwater for the transport and remediation of pollutants in aeration zones and aquifers. In this work, polystyrene latex microspheres with diameter of 1 渭 m were used as simulated colloidal particles and quartz sand as porous media. The effect of ionic strength on colloid adsorption and migration in saturated steady flow was studied by laboratory soil column experiments. The effects of hydrocolloid and ionic strength on the transport of heavy metal As~(3 were studied. According to the concentration penetration curve obtained in the experiment, the colloid adsorption rate is calculated and the migration rate is removed. According to the DLVO theory, the potential energy diagram is drawn and the experimental results are quantitatively analyzed. The experimental results show that the adsorption amount of the colloid on the porous media increases with the increase of ionic strength of the solution. When the ionic strength of the solution is 50 mm ~ (2) ~ (60) mm ~ (-1) ~ (70 mm), the percentage of colloid in the sand column is 92.96 ~ 94.62 ~ 94.782 ~ 94.78 ~ (2), respectively. The change of the ionic strength of the solution can cause the colloid to migrate again. The change of ionic strength of the solution was the same, the colloidal remigration was the largest and the remigration rate was 3.88 when the ionic strength was reduced from 50 mm to 10 mm, and the initial ionic strength was 60 mm, and the colloidal remigration was the largest when the ionic strength decreased to 10 mm. The remigration rate is 1.75. The colloidal remigration rate of the background solution is higher when the electrolyte solution is directly converted to ultra-pure water than when the solution is first converted to the low-concentration electrolyte solution and then to the ultra-pure water. The results show that the migration of colloids in saturated porous media is not only affected by the ionic strength, but also by the change rate of ionic strength and the chemical history of solution. Water ore colloids can adsorb As~(3) and inhibit the migration of As~(3) in saturated sand columns, and the adsorption capacity increases with the increase of ionic strength. 4) when the distribution of hematite colloids in the sand columns is more dispersed, the adsorption sites of the hematite colloids increase because of the increase of adsorption sites. The contact time with the colloid increased and the retention in the sand column was larger than that at the top of the sand column, indicating that the effect of the colloid on the migration of As~(3 in saturated porous media was greater than that on the ionic strength. The above results can provide theoretical basis and decision basis for the formulation of water and soil health standards and the prevention and control of groundwater contamination by organic colloids such as pathogenic microorganisms and various organic and inorganic pollutants carried by colloidal particles.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53;X523

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