【作者】 孙华；

【导师】 陈邦林； 陆维昌；

【作者基本信息】 华东师范大学 ， 物理化学， 2004， 硕士

【摘要】 在自然水体中存在有许多活性物质，这些物质大多具有疏水部分和亲水部分两个部分。这些两亲分子往往停留在气-液界面上，在水体表层有不同程度的富集，形成了表面膜。在自然水体的气-液界面上，腐殖质类物质形成的膜占主导地位，这些物质大多是醣朊和蛋白多糖的氧化降解产物，这些表面膜聚集在气—液界面上，极大的影响了气-液界面上许多动态、非平衡的过程。由于许多有机物和无机物的交换、气体的交换、水蒸气的交换、热量和动量的交换都是表面膜居间促成的，且这些过程与界面上活性物质的浓度有关。因此确定表面膜内主要的化学和生物组分以及测量它们形成、改变、消失的速率有着至关重要的作用。对表面膜的测量研究方法有很多，包括光学显微镜、X射线、波阻尼法、光谱方法、表面膜电位法、表面膜压法等。而最直接的方法莫过于表面膜压法，它不需要对样品进行预处理，不破坏表面膜，因此能准确的测定表层的性质，可获得许多关于单个分子的大小、形状以及取向等方面的信息。 本文研究腐植酸在气—液界面上的物理化学行为以及腐植酸与金属盐在气—液界面上的物理化学行为将有助于理解自然水体中的水气转移过程。实验结果表明： 1)由于腐植酸主要由多种活性较高的化学功能团构成，包括较多的疏水性脂肪烃类的C-H基团以及较为亲水的羧基、羟基等基团，因此水体中的腐植酸在气—液界面上可以部分富集，形成表面膜，并且随着样品量的增加，膜压也随之增加，出现的滞后环面积也随之增加。 2)本实验的研究结果表明金属盐在与腐植酸作用时，可能包括如下几个方面的作用，金属盐不仅仅通过压缩胶体的双电层，降低静电排斥而促进聚集形成，可能产生更多的疏水结构，从而使得表面膜压增加，另外它们可能通过与腐植酸络合，中和聚合物链上的负电荷，从而减少了腐植酸分子间的排斥力，从而进一步加强了聚沉的倾向，由于金属盐能使腐植酸更容易聚集，因而使得表面膜更容易凝聚，这从金属盐与腐植酸混合后所形成的表面膜的谱图中可以反映出来，表面张力下降的过程更为陡峭。譬摘要 另外，本文对滞后环形成原因进行初步探讨，认为滞后环的形成可能是由于下列原因造成的:1.与仪器驱动力的频率有关(即与整个压缩一膨胀过程所需的时间有关)。2.与膜分子的脱附一扩散行为有关3.表面结构的改变(包括胶束的形成、膜崩溃、相变)4.接触角的滞后效应 并根据前面对滞后环形成原因的探讨，从理论上初步解释说明滞后环的形成原因。更多还原

【Abstract】 There are many active substances in natural waters extensively. Most of substances have two moieties, one is hydrophobic moiety and the other is hydrophilic moiety. These amphipathic molecules reside at the gas-liquid interface. The surface-active organic substances tend to be enriched at air-liquid interface and make up of natural film. In these natural film at the air-water interface, film made up of humus substances hold leading station. Humus substances mostly are result from oxygenation and degradation of carbohydrate and albumen polysaccharide .The natural film at the air-water interface influences on a lot of dynamic and non-equilibrium processes. The exchange of organic and inorganic matter, gases, water vapor, heat and momentum may be mediated by the surface film at the air-water interface. Being the relationship between concentration of surface-active organic substances at the air-water interface and these processes, it is of fundamental importance to determine the basic chemical and biological composition of surface films and to measure their rates of formation, alteration and disappearance. Monolayer techniques used for the study of surface film at the air-water interface provide a lot of information of film molecules, including optic microscope, x-ray, wave damping, spectroscopy, surface potential measurement, surface pressure measurement. In these study methods, surface pressure measurement has great advantages, such as no pretreatment and no destructive film. It can be depicted property of surface film exactly and provides information about the molecular orientation and changes at the interface.We study physicochemical behavior of humic acid at gas-liquid interface and metal-humic interactions. From experiments we conducted, we got some important results which administer to the understanding the exchange of water and vapor in natural water system.1) Humic acid form mainly from various active chemical function group, including hydrophobic alkyl (C-H) and t hydrophilic function group (-COOH, -OH).Due to the accumulation of humic acid in natural water systems onto air-water interface, the surface film is forming. Increasing quantity of humic acid, surface pressure and area of hysteresis loop will be increased too.2) The results indicated that metal-humic interactions contained a few kinds of principle. The increased cation concentration could be causing a compression of the colloidal double layer, reducing the inter-molecular repulsion, accelerating colloidal aggregation , producing a more hydrophobic structure and increasing surface pressure. The metals could be forming chemical bonds with the functional groups in the humic acid structure, neutralising the humic charge and hence reducing the inter-molecular repulsion. They may further enhance the tendency for flocculation between humic molecules. Because metallic cation can accelerate aggregation of humic acid, surface film show agglomerate property. The diagram of surface film formed by metal-humic interactions showed that surface tension drop abruptly.In the paper, we discussed that the mechanisms were responsible for the hysteresis. It is likely that some mechanisms are responsible for the hystersis.1. Frequency of instrumental (cycle of compressible-expansible process )2. Desorption-diffusion of film3. Changing of surface structures such as micelles, phase changes in the film and collapse of the film.4. Contact angle hysteresisBased on the hypothesis who should be responsible for the hysteresis, we explain the forming of hysteresis loops by modeling.更多还原