Industry/University Cooperative Research: Adsorption of Modified Surfactants from Aqueous Solution

摘要：表面活性剂在水溶液中的吸附是一种重要而复杂的现象，受表面活性剂结构（官能团、链长、分支）、固体矿物学、形态非均质性和溶液性质等因素的影响。本文通过研究表面活性剂与矿物、溶解矿物、聚合物、油和醇的相互作用来研究表面活性剂的吸收（损失）。为了了解吸附现象，在之前的拨款中，监测了其他关键性质，如zeta电位、润湿性、CMC、矿物溶解和表面活性剂色谱分离。结果表明，当存在可溶性和半可溶性固体时，不仅会由于表面沉淀而改变固体，而且会由于大块沉淀而耗尽表面活性剂。除静电和半束吸收外，表面活性剂的沉淀是造成表面活性剂损失的一个主要原因，特别是在含有金属离子的溶液中。现在看来，表面活性剂可以经过适当的修饰，以适应这种恶劣的环境。特别强调的是乙氧基表面活性剂，因为它们可以被操纵以产生所需的界面张力和耐盐性。在含有通常对磺酸盐非常不利的底物的石膏中，PI已经获得了与某些乙氧基化磺酸盐的沉淀的完全抑制。结构修饰（如乙氧基化）的作用尚不完全清楚，但可以使用多种技术进行研究。目的是研究（利用吸收、电动、色谱和光谱技术）。结构修饰影响吸收/沉淀的机制，并确定在上述表面活性剂混合体系中观察到的选择性/优先吸收或协同作用的原因。独特与创新：与其他吸收方面的研究相比，本研究还包括固体溶解对吸收的影响，以及溶解物质与表面活性剂的相互作用导致络合甚至沉淀。固体总是溶解的，溶解的物质常常控制整个吸收（抽象）行为，但这些影响在过去被忽略了。在本研究中，定量地确定了溶解物种的影响，并解释了吸收/解吸现象和滞后现象。

RESEARCH SUMMARY: Adsorption of surfactants from aqueous solution is an important but complex phenomenon due to the influence of factors including surfactant structure (functional groups, chain length, branching), solid mineralogy and morphological heterogeneity and solution properties. Absorption (loss) of surfactants is investigated here by studying their interactions with minerals, dissolved mineral species, polymers, oils and alcohols. In order to understand the absorption phenomenon, in the previous grant, other key properties such as zeta potential, wettability, CMC, mineral dissolution and surfactant chromatographic separation were monitored. It was shown that when soluble and semisoluble solids are present, there will be not only alterations of the solids due to surface precipitaiton but also depletion of surfactants due to bulk precipitation. A major process responsible for surfactant loss has been identified to be, in addition to electrostatic and hemimicellar absorption, surfactant precipitation particularly in solutions containing metal ions. It appears now that surfactants can be suitably modified to tolerate such hostile environments. Particular emphasis is being placed on ethoxylated surfactants since they can be manipulated to yield desired interfacial tension and salt tolerance. The PI has already obtained total inhibition of precipitaton with certain ethoxylated sulfonates in gypsum containing substrates which are normally very hostile to sulfonates. The role of structural modifications such as ethoxylation is not fully understood, but can be studied using a combination of techniques. It is the aim of the proposed work to investigate (using absorption, electrokinetic, chromatographic and spectroscopic techniques). The mechanisms by which structural modifications affect absorption/precipitation and to identify the reasons for the selective/preferential absorption or synergism observed in mixed systems of the above surfactants. UNIQUENESS AND INNOVATION: In contrast to other work on absorption, this research includes also the effects on absorption of dissolution of the solid and interaction of the dissolved species with the surfactant leading to complexation and even precipitation. Solids invariably dissolve and the dissolved species often govern the entire absorption (abstraction) behavior and yet these effects have been ignored in the past. In this research, the effect of dissolved species is being quantitatively determined and the absorption/desorption phenomenon and hysteresis phenomenon explained.