Knowledge Resource Center for Ecological Environment in Arid Area
| 高盐沙地生态固沙用共聚乳液的结构特点及耐盐机理 | |
| 其他题名 | Structure characteristics and mechanism of salt tolerance of developed emulsions focusing on the ecological sand-fixing in salty desert |
| 龚伟 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 刘白玲 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 在自然条件脆弱的环境背景下，经济原因驱使人们盲目开荒；不成熟的管理方式和灌溉技术通常导致地下水位上升，将地下水中的矿物质带入土体，加之蒸发强烈，使土壤中盐分增加。高盐度和缺水的条件，使植物无法正常生长，土地在没有植被覆盖的情况下，裸露的盐渍地面极易遭受风沙的侵蚀，使土壤中的养分进一步减少。久而久之，形成了盐渍沙化地，造成土地生产力的长期丧失。我国是世界上受盐渍沙化地危害最为严重的国家之一，目前，我国盐渍沙化地面积共有75万平方公里，占沙漠化总面积的28.9%，遍及我国17个省、市、自治区。盐渍地沙漠化作为极其重要的环境和社会问题，正困扰着当今世界，威胁着人类的生存和发展。防止盐渍地沙漠化和对盐渍沙化地的治理，在世界范围内引起了广泛的关注。世界各国都把遏制盐渍地沙漠化作为生态环境建设和可持续发展的重要课题。要抑制日益猖狂的盐渍地沙漠化势头，必须首先进行固沙。长期以来，在高盐沙地治理的过程中，一直存在着固沙材料耐盐性能差、易粉化的问题。迄今为止，还没有可对高盐沙地进行治理的有效材料。面对我国高盐沙地面积仍在扩大的严峻态势，开发出能有效遏制高盐沙地的适用材料及方法，是一项十分紧迫的艰巨任务。本论文从材料学角度出发，深入分析了高盐沙地固沙对材料性能的要求，从材料的结构设计入手，制备了多个适合于高盐沙地固沙、并具有生态效应的新型高分子材料，系统研究并阐明了固沙材料结构与固沙性能的相互关系，以及固沙材料在高盐沙地固沙中的作用机理。研究内容和取得的主要结果如下：1. 乳化体系是成功实现乳液聚合的关键因素。由于阳离子表面活性剂对微生物的生长具有抑制作用，因此选用阴离子与非离子表面活性剂作为制备高盐沙地生态固沙乳液的乳化体系。通过光谱法和相体积分数-盐含量相图测试了所选用表面活性剂的耐盐性，研究了选用表面活性剂对大肠杆菌生长的影响。试验结果表明SDS与LF具有优异的耐盐性能和良好的生态效应。在此基础上，进一步探讨了SDS和LF与沙粒的吸附行为，结果显示SDS和LF与沙粒之间均具有良好的吸附行为，且沙粒中盐含量的增加有利于二者间的吸附，符合Langumir吸附行为。最后考察了SDS和LF对沙土微生物生长的影响。以上试验结果表明，SDS与LF可组成高盐沙地生态固沙材料的复合乳化体系。2. 采用种子乳液聚合法，成功制备了P(VAc-DBM-AA-AMPS)四元共聚阴离子型乳液，并首次将其用于高盐沙地固沙。考察了功能单体AMPS对P(VAc-DBM-AA-AMPS)四元共聚乳液合成与基本性能的影响。发现AMPS的引入，对制备乳液的粒径和粘度有很大的影响；AMPS的引入，较大幅度地提高了共聚乳液形成胶膜的耐盐性。同时详细考察了P(VAc-DBM-AA-AMPS)共聚乳液的保水性、固沙强度、耐热老化、抗冻融稳定性等，探讨了共聚乳液形成胶膜的力学性能与固沙时固沙强度之间的关系。结果表明，通过AMPS功能单体的引入，阴离子型P(VAc-DBM-AA-AMPS)乳液具有良好的保水能力、抗热老化及冻融稳定性，且该共聚乳液形成胶膜的拉伸强度与固沙时的固沙强度呈现正相关性。3. 为了进一步提高材料的固沙强度，设计并制备了P(VAc-DBM-AA-SSS)四元共聚阴离子型乳液。考察了功能单体SSS对P(VAc-DBM-AA-SSS)共聚乳液合成与基本性能的影响。同时详细探讨了P(VAc-DBM-AA-SSS)乳液作为高盐沙地固沙材料用的保水性、固沙强度、抗热老化、抗冻融稳定性等性能。该阴离子型的P(VAc-DBM-AA-SSS)乳液作为高盐沙地固沙材料使用，具有良好的固沙强度，较低的固含量便就能满足抗风蚀性能的要求，并具有良好的抗热老化及抗冻融稳定性，但保水性能较差。4. 为了使高盐沙地用固沙材料兼具固沙效果与有良好的保水性，设计并制备出了P(VAc-DBM-AM-DMAPS)四元共聚两性乳液。考察了两性功能单体DMAPS对P(VAc-DBM-AM-DMAPS)共聚乳液合成与基本性能的影响。发现功能单体DMAPS的引入，不但提高了所制备乳液耐CaCl2的稳定性；而且还提高了制备乳液在盐溶液中黏度。同时详细探讨了P(VAc-DBM-AM-DMAPS)乳液成膜后的力学性能，以及该乳液作为高盐沙地固沙材料用的保水性、固沙强度、抗热老化、抗冻融稳定性等性能。结果表明，P(VAc-DBM-AM-DMAPS)乳液具有良好的固沙强度，较低的固含量便就能满足抗风蚀性能的要求，并具有良好的保水性能、抗热老化及抗冻融稳定性，揭示了材料结构与固沙性能之间的内在联系。5. 在试验室植物栽培实验中发现，所制备的固沙材料喷洒在含盐沙土表面后，能够促进植物的发芽及生长；从对采自喷洒不同材料后沙土中的细菌、放线菌和真菌生态分布的分析中发现，不同分子结构的乳液，对沙土微生物的生长有不同的影响；但P(VAc-DBM-AM-DMAPS)乳液的使用，可促进沙土中大部分微生物的生长。6. 乳液在高盐沙地固沙的作用机理不同于在不含盐沙地固沙的固沙机理。在高盐沙地固沙过程中，固沙剂喷洒于沙面后，小部分液滴渗入沙体内，而剩余的大部分液滴则滞留在沙地表面，此时固沙剂中的水相可溶解沙土中的NaCl。在自然条件下固化时，NaCl将会随着水分的蒸发向沙土表面迁移，并以晶体形式析出，分散在聚合物膜中。由于NaCl具有高的吸湿性，聚合物膜中的NaCl一直处于吸潮、颗粒表面溶解、水分蒸发晶体再析出的过程，从而形成硬的团聚体。硬团聚体的形成将严重破坏高分子膜的连续相，使得膜的机械性能下降，从而降低了聚合物用于高盐沙地的固沙效果。7. 面对高盐沙地自然环境，所制备的三种材料的固沙性能仍会出现较大幅度的下降，针对这一问题，研究了不同类型表面活性剂对NaCl结晶行为的影响，发现LF能有效减小NaCl结晶粒子尺寸。同时详细地探讨了添加LF后对含盐乳液形成胶膜的热性能及力学性能的影响，以及添加LF后乳液固沙性能的变化。试验结果表明，添加LF能极大地提高乳液在自然环境下对高盐沙地的固沙效果，这不仅再次证实了乳液在高盐沙地固沙的作用机理，而且为在高盐沙地固沙的实施技术提供了思路。 |
| 英文摘要 | Under the fragibility of the ecological environment, economic reasons play an important role in accelerating the formation of soil salinization in arid and semi-arid desert regions. The immature management style and irrigation technology often lead to the rise of ground-water level. The groundwater typically contains solutes of varying concentrations, and its utilization may noticeably affect soil characteristics. In additional, the intense evaporation tends to accumulate salts in the upper soil pro?le, especially when it is associated with an insuf?cient leaching or where soluble salts move upward in the soil pro?le from a water table instead of downward. With the accumulation of excess salinity and shortage of available water in soil, this causes that plants can't normal growth. And with the extension of time, the degraded saline land usually caused numerous adverse phenomena, such as nutrients poorness, desertization and forming salty desert. China is one of the countries affected seriously by salty desert in the world. So far, in China, there were over an area of 75 square kilometers of salt-affected soils suffering desertization, accounting for 28.9% of the total area of the desertification and occurring mainly in 17 provinces, municipalities and autonomous regions.Salty desert as an extremely important environmental and social issue is plaguing today's world. It is a threat to the human survival and economic development. Every country in the word regards control of high salt-affected sandy land as an important issue of ecological environment and sustainable development. In order to suppress the increasing of rampant saline land desertification, the sand fixation under high salt stress was regarded as the key step for salty desert restoration. For a long time, in the process of controlling salty desert, the sand-fixing materials used in salt-affected sandy land were ongoing problems, such as poor salt resistance and easy pulverization. So far, there have been no effective sand-fixing materials for salty desert restoration. In order to solve this problem that salt-affected soils suffering desertization is still expanding, the development of the new sand-fixing materials for salty desert restoration is a very pressing task. Therefore, through analyzing and studying the requirement of sand-fixing materials used in salty desert from the principle of materials science, firstly. And then based on the structure design of materials, the preparation and performance of the novel ecological sand-fixing materials were studied in the paper, moreover, systematic study and illuminate the correlations between the structure of sand-fixing material and the sand fixation ability. And then, we further analyze and study the sand-fixing mechanism of emulsion in salty desert. The research content and main results of this thesis are drawn as below:1. The influence of emulsifying system on the preparation emulsions was often a matter of major concern. Due to the cationic surfactant has inhibitory effect on the growth of microorganisms, so, we choose anionic and non-ionic surfactants as the emulsified system for preparation ecological sand-fixing materials. Firstly, the salt tolerance of surfactant has been investigated by the spectrophotometric and phase volume method, and then studied the effects of surfactants on the growth of Escherichia coli. The experimental results show that the SDS and LF had excellent salt resistance and good ecological effect. On this basis, the adsorption of the two types of SDS and LF onto sand particles from aqueous solutions was systematically studied. the results showed that SDS and LF between sand grains have good adsorption behavior, with increasing salinity, the adsorption of SDS and LF on sand particle adsorbent was favored and following the Langmuir isotherm model. Finally, it was found SDS and LF at the tested concentrations was harmless to the growth soil microbe. These results indicated that surfactant (SDS and LF) in enhanced the sand-fixing ability of emulsion used for high salt-affected sandy land had excellent salt tolerance, ecological effect and high adsorption efficiency on sand particles surface.2. The anionic poly (vinyl acetate-dibutyl maleate-acyclic acid-co-2-acrylamido-2-methyl propanesulfonic acid) (P(VAc-DBM-AA-AMPS)) copolymer emulsions were successfully prepared using the seed emulsion polymerization technique, which used for high salt-affected sand fixation in the first time. The influence of AMPS functional monomer on the synthesis of P(VAc-DBM-AA-AMPS) copolymer emulsions was investigated in details in the preparation process. It was found that AMPS monomer had great effect on the particle size and the viscosity. The salt tolerance property of film is increased when AMPS functional monomer is introduced. Meanwhile, the sand-fixing properties of P(VAc-DBM-AA-AMPS)copolymer emulsions were investigated in details, which including water retaining, compressive strength, thermal aging and freeze-thaw stabilities. Moreover, the relationship between mechanical properties of film and the sand fixation ability of the emulsion was studied. The results show that the anionic P(VAc-DBM-AA-AMPS) copolymer emulsions have good water retaining capacity, and it has good thermal aging and freeze-thaw stabilities to withstand the changes in temperature by introducing AMPS functional monomer. And the positive correlation existed between the tensile strength of film and the sand fixation ability of the emulsion.3. In order to improve the properties of sand-fixing capability for sand-fixing materials, we designed and prepared P(VAc-DBM-AA-SSS)anionic emulsion. The influence of SSS functional monomer on the synthesis of P(VAc-DBM-AA-SSS) copolymer emulsions was investigated in details in the preparation process. Meanwhile, the sand-fixing properties of P(VAc-DBM-AA-SSS)copolymer emulsions were investigated in details, which including water retaining, compressive strength, thermal aging and freeze-thaw stabilities. The results show that the anionic P(VAc-DBM-AA-SSS) copolymer emulsions have good anti-wind erosion ability, the fewer solid content of the emulsion will be able to meet the anti-erosion performance. And it has good thermal aging and freeze-thaw stabilities to withstand the changes in temperature by introducing SSS functional monomer. However, Compared to P(VAc-DBM-AA-AMPS) emulsion, P(VAc-DBM-AA-SSS)emulsion showed worse water retention performance in the sand fixation.4. In order to improve the properties of sand-fixing capability, water retention and eco-performance for sand-fixing materials, we designed and prepared P(VAc-DBM-AM-DMAPS)amphoteric emulsion. Firstly, the influence of DMAPS functional monomer on the synthesis of P(VAc-DBM-AM-DMAPS) copolymer emulsions was investigated in details in the preparation process. It was found that the CaCl2 tolerance property of the emulsion is improved and the viscosity of the emulsion in NaCl solution is increased when DMAPS functional monomer is introduced. And then, the mechanical properties of film were studied in detail. Meanwhile, the sand-fixing properties of P(VAc-DBM-AM-DMAPS)copolymer emulsions were investigated in details, which including water retaining, compressive strength, thermal aging and freeze-thaw stabilities. The results show that the amphoteric emulsions have good anti-wind erosion ability, the fewer solid content of the emulsion will be able to meet the anti-erosion performance. And it has good water retaining capacity, thermal aging and freeze-thaw stabilities to withstand the changes in temperature. And the correlation between the structure of sand-fixing materials and the sand fixation ability of the emulsion were revealed, also.5. In the results of plant cultivation experiments, the sand-fixing material has no negative effect on the germination and growth of plant. It was found in the analysis of ecological distribution of bacteria, actinomycetes and fungi collected in the sand after spraying different materials. Different emulsions have different effects on the growth of sand microbial. However, the growth of most sand microbial can be increased after using P(VAc-DBM-AM-DMAPS) emulsion.6. Based on above mentioned experimental results, we analyzed the mechanium about the emulsion used as sand-fixing material to fix salty desert in practical application. When the emulsion was sprayed on the surface of salty soil, the water from the emulsion could dissolve NaCl in salty desert. And then, as evaporation proceeded slowly under natural condition, the NaCl concentration in the dispersing liquid increased and the NaCl would migrate to the sand surface. When the NaCl concentration increased up to a maximum concentration, the further drying would cause crystallization of NaCl. At last, NaCl crystals dispersed in latex film. However, due to high hygroscopicity of the NaCl crystals, the crystallization of NaCl in latex film would repeat crystallization and dissolution cycles. With repeated cycles of crystallization and dissolution a small number of nuclei formed which grew to bigger hard aggregations. These hard aggregations would serious damage to continuous phase of the latex film. So, in practical application, the sand-fixing capability of the emulsion decreased during wet-dry cycles.7. Facing natural environment of salty desert, the sand-fixation performance of three kinds of prepared sand-fixing materials was sharp declined. In order to solve this problem, firstly, the effects of different kinds of surfactants on the crystallization behavior of NaCl were studied in detail. It was found that LF can effectively decrease the size of NaCl crystal particles. Meanwhile, Adding LF into the emulsions can improve the mechanical properties of film. The results of sand-fixing experiment show that adding LF can greatly improve anti-wind erosion ability and water retaining capacity of emulsion used in salty desert under the natural environment, and it was not only once again confirmed that the sand-fixing mechanism of the emulsion applied in salty desert, but also provided useful train of thought and implementing technology for sand-fixation in salty desert. |
| 中文关键词 | 生态固沙 ; 高盐沙地 ; 分子结构 ; 表面活性剂 ; 耐盐机理 |
| 英文关键词 | Ecological sand-fixing，Salty desert， Molecular structure， Surfactants， Mechanism of sand-fixation |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 高分子化学与物理 |
| 来源机构 | 中国科学院成都有机化学研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287638 |
| 推荐引用方式 GB/T 7714 | 龚伟. 高盐沙地生态固沙用共聚乳液的结构特点及耐盐机理[D]. 中国科学院大学,2016. |
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