Mechanisms of Cleaning Organic Films from Solid Substrates using Aqueous and Organic Solvents

C. Grant/ P. Carbonell NC State这项工作的主要目的是获得清洁机制的基本见解，以开发环境友好的清洁替代品。实验将得到关于使用非离子表面活性剂水溶液与有机溶剂结合从旋转圆盘上去除有机膜的动力学信息。这样的动力学信息提供了深入了解清洗过程的机制。由于水相和有机相固有的不混溶性，将污染物划分为有机相是可能的。这使得水相可以循环利用，减少了产生的清洁废物的总量。可以对两相进行分析，以进一步了解所得乳液的稳定性以及表面活性剂与有机溶剂的相互作用。在此之前，我们小组的工作使我们能够更好地理解胶束和亚胶束非离子表面活性剂水溶液去除旋转圆盘上枞酸膜的机理。从之前的工作中，我们发现清洗过程分为三个阶段。第一种状态是由有机相通过表面活性剂的渗透和随后的从界面到整体水溶液的传质而实现的增溶控制的。在第一阶段，薄膜从水溶液中吸收水分，降低其粘度，直到液滴在剪切力的作用下开始在圆盘表面移动。这些液滴聚集成螺旋形的连续溪流，有机相通过这些溪流流动，直到它离开圆盘边缘。这种行为发生在清洗的第二阶段，其去除速度明显快于第一阶段。水流最终破裂，进入第三阶段，去除率较低，其去除机制显然是在剪切力作用下有机相滴的卷起。照片显示在不同清洗阶段的膜结构的形态提供了实验证据，支持所描述的机制。推导了一个模型，该模型将清洗速率的经验观察与描述溶解膜流体动力学的物理参数联系起来。拟议的研究将调查两种污染物：枞酸和聚丁烯从不同的固体底物中去除的流体动力学、溶解和分配的综合速率。，外窥玻璃层压板，铜，镍)。本工作还将研究污染废水的相分离行为，以努力回收清洗液。我们的研究将是独一无二的，因为有机溶剂将与水非离子表面活性剂溶液结合使用，从而允许水清洗液的重复使用。拟议的研究将通过NSF GOALI计划与北卡罗来纳州三角研究园的CORPEX技术公司合作进行。CORPEX技术公司生产的清洁解决方案是表面活性剂和有机溶剂的组合。CORPEX技术公司进行的初步实验已经确定，在水溶液中加入有机溶剂，当与表面活性剂一起使用时，可以提高清洗速度。此外，一旦清洗完成，有机溶剂可以从水溶液中相分离。有机污染物（即油脂或油）进入有机相，留下非常干净的水溶液。这样可以最大限度地减少废水的产生，只产生少量的有机废物。在之前专门使用水性清洁剂的工作中，使用紫外吸收检测器连续测量从旋转盘中去除的污染物量，作为散装清洁溶液中时间的函数。然而，随着有机溶剂的加入，清洗液变得浑浊。因此，不能使用紫外吸收等光学技术。为了避免这个问题，放射性示踪剂将与有机污染物混合。这种污染物将被自旋涂覆在磁盘上，形成均匀的薄膜。在清洗实验中，将使用在线液体闪烁分析仪连续检测从磁盘上去除的污染物量。非均匀闪烁分析仪通过将样品通过固体珠子而不是混合液体鸡尾酒来产生闪烁。该项目获得的基本清洁信息将有助于CORPEX技术公司继续开发环境友好型清洁解决方案。大部分实验工作将在北卡州立大学完成。然而，靠近CORPEX将加强技术互动，并使技术从NCSU快速转移到CORPEX。

ABSTRACT CTS-9616638 C. Grant/ P. Carbonell NC State The main objective of this work is to obtain fundamental insight into cleaning mechanisms in order to develop environmentally benign cleaning alternatives. Experiments will yield kinetic information about the removal of organic films from rotating disks using aqueous nonionic surfactant solutions in conjunction with organic solvents. Such kinetic information gives insight into the mechanism of cleaning processes. Because of the inherent immiscibility of the aqueous and organic phases, it is possible to partition the contaminant into the organic phase. This enable the aqueous phase to be recycled, reducing the total volume of cleaning waste generated. Both phases can bne analyzed to gain further insight to the stability of the resulting emulsion and the surfactant interactions with the organic sovent. Prior to work by our group has allowed better understanding of the mechanism for abietic acid film removal from rotating disks using micellar and submicellar aqueous nonionic surfactant solutions. From prior work, it was discovered that cleaning occurs by a three stage process. The first state is controlled y the solubilization of the organic phase through surfactant penetration and subsequent mass transfer from the interface to the bulk aqueous solution. During the first stage, the film absorbs water from the aqueous solution reducing its viscosity, until drops start to move on the disk surface under the action of shear forces. These drops aggregate into spiral-shaped continuous rivulets through which the organic phase flows until it comes off the disk edge. Such behavior occurs during the second stage of cleaning, which has a rate of removal appreciably faster than the first stage. The rivulets eventually break, leading to a third stage with lower removal rates, in which the removal mechanism is apparently the roll up of organic phase drops under the action of shear forces. Photographs showing the morphology of the film structure in the different cleaning stages provide experimental evidence that supports the described mechanism. A model was derived that relates the empirical observations of cleaning rates to physical parameters describing solubilizing film hydrodynamics. The proposed research will investigate the combined rates of hydrodynamics, dissolution, and partitioning in the removal of two contaminants: abietic acid and polybutene form different solid substrates(i.e., exopy-glass laminate, copper, nickel). This work will also study the phase separation behavior of the contaminated effluent in an effort to recycle the cleaning solution. Our research will be unique because an organic solvent will be used in conjunction with an aqueous nonionic surfactant solution allowing for reuse of the aqueous cleaning solution. The proposed research will be carried out in collaboration with CORPEX Technologies, Inc. in Research Triangle Park, NC through the NSF GOALI program. CORPEX Technologies manufactures cleaning solutions that are combinations of surfactants and organic solvents. Preliminary experiments conducted at CORPEX Technologies have determined that the addition of an organic solvent to an aqueous solution will increase the rate of cleaning when used with surfactants. In addition, once cleaning is complete the organic solvent can be phase separated from the aqueous solution. The organic contaiminant (i.e.,grease or oil) partitions into the organic phase, leaving a very clean aqueous solution. This minimizes waste water generation and produces only a small amount of organic waste. In prior work exclusively with aqueous based cleaners, the amount of contaminant removed from the rotating disk was continuously measured as a function of time in the bulk cleaning solution using a UV absorbance detector. With the addition of an organic solvent, however, the cleaning solution becomes turbid. As a result, optical techniques such as UV absorbance can not be used. To circumvent t his problem, radioactive tracers will be mixed with the organic contaminant. This contaminant will be spin coated onto the disk to form a uniform film. During cleaning experiments, an on-line liquid scintillation analyzer will be employed to continuously detect the amount of contaminant removed from the disk. The heterogeneous scintillation analyzer created scintillation by passing the sample over solid beads as opposed to mixing with a liquid cocktail. The fundamental cleaning information obtained by this project will assist CORPEX Technologies in its continuing development of environmentally friendly cleaning solutions. The majority of the experimental work will be done at NCSU. However, the close proximity to CORPEX will enhance the technical interaction and enable a rapid transfer of technology from NCSU to CORPEX.