Department of Chemical Engineering and Chemical Technology, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.
J Colloid Interface Sci. 2017 Apr 1;491:286-293. doi: 10.1016/j.jcis.2016.12.054. Epub 2016 Dec 24.
Ionic liquids can serve as an environmentally-friendly replacement for solvents in emulsions, therefore they are considered suitable to be used as an emulsified medium for various active materials one of which are extractors of metal ions. Increasing the extraction efficiency is considered to be one of the key objectives when working with such extraction systems. One way to improve the extraction efficiency is to increase the contact area between the extractant and the working ionic solution. This can be accomplished by creating a nano-emulsion of ionic liquid containing such an extractant. Since emulsification of ionic liquid is not always possible in the sample itself, there is a necessity of creating a stable emulsion that can be added externally and on demand to samples from which metal ions need to be extracted. We propose a method of fabrication of a highly-stable extractant-loaded ionic liquid-in-water nano-emulsion via a low-energy phase reversal emulsification followed by continuous layer-by-layer polyelectrolyte deposition process to encapsulate the nano-emulsion and enhance the emulsion stability. Such a multilayered stabilized nano-emulsion was tested for extraction of Cd and Ca ions in order to determine its extraction efficiency and selectivity. It was found to be effective in the extraction of Cd ions with near 100% cadmium removal, as well as being selective since no Ca ions were extracted. The encapsulated emulsion was removed from samples post-extraction using two methods - filtration and magnetic separation, both of which were shown to be viable under different circumstances - larger and mechanically stronger capsules could be removed by filtration, however magnetic separation worked better for both smaller and bigger capsules. The long-term stability of nano-emulsion was also tested being a very important characteristic for its proposed use: it was found to be highly stable after four months of storage time.
离子液体可以作为乳化剂中溶剂的环保替代品，因此被认为适合用作各种活性物质的乳化介质，其中之一是金属离子的萃取剂。提高萃取效率被认为是使用此类萃取系统的关键目标之一。提高萃取效率的一种方法是增加萃取剂与工作离子溶液之间的接触面积。这可以通过创建含有这种萃取剂的离子液体纳米乳液来实现。由于在样品本身中并不总是可以乳化离子液体，因此需要创建一种稳定的乳液，可以根据需要外部添加到需要提取金属离子的样品中。我们提出了一种通过低能量相转变乳化法制备高度稳定的负载萃取剂的离子液体-水纳米乳液的方法，然后通过连续的层层聚电解质沉积过程来封装纳米乳液并增强乳液稳定性。这种多层稳定的纳米乳液被测试用于提取 Cd 和 Ca 离子，以确定其萃取效率和选择性。结果表明，它在提取 Cd 离子方面非常有效，几乎可以完全去除 Cd 离子，并且具有选择性，因为没有提取 Ca 离子。萃取后，使用两种方法（过滤和磁分离）从样品中去除封装的乳液，这两种方法在不同情况下都可行——较大且机械强度较高的胶囊可以通过过滤去除，而较小和较大的胶囊则更适合磁分离。还测试了纳米乳液的长期稳定性，这是其预期用途的一个非常重要的特征：在储存四个月后，发现其非常稳定。
