Application of structural analogs of dimercaptosuccinic acid-functionalized silica nanoparticles (DMSA-[silica]) to adsorption of mercury, cadmium, and lead
Application of structural analogs of dimercaptosuccinic acid-functionalized silica nanoparticles (DMSA-[silica]) to adsorption of mercury, cadmium, and lead
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二巯基丁二酸功能化二氧化硅纳米粒子（DMSA-[二氧化硅]）结构类似物在汞、镉和铅吸附中的应用
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发表时间：
2011
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通讯作者：
M. Bruce
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作者：
A. A. A. Hamid;C. Tripp;A. E. Bruce;M. Bruce
为了进一步了解纳米级DMSA-[二氧化硅]对汞的选择性，我们研究了一系列与DMSA相关的配体，这些配体是：单巯基琥珀酸; MMSA，2-巯基-4-甲基-5-噻唑乙酸; MCT，邻硫代水杨酸; o-TSA和对硫代水杨酸; p-TSA。MMSA螯合物在结构上类似于DMSA，除了它仅具有一个硫醇基团。螯合物o-TSA和p-TSA各自具有一个硫醇和一个羧酸基团。MCT包括靠近硫醇盐结合位点的中性S和N原子。MCT、o-TSA和p-TSA在具有相同数量的羧酸和硫醇基团方面彼此相似，并且预计与二氧化硅上的连接体形成酰胺键会消除羧酸盐结合位点，使硫醇盐成为纳米尺寸; MMSA-[二氧化硅]、MCT-[二氧化硅]、o-TSA-[二氧化硅]和p-TSA-[二氧化硅]中Hg（II）、Cd（II）和Pb（II）金属离子的唯一结合位点。与溶液中相同的游离螯合物相比，纳米尺寸的MMSA-[二氧化硅]、MCT-[二氧化硅]、o-TSA-[二氧化硅]和p-TSA-[二氧化硅]中的每一种分别显示出对Hg（II）比Cd（II）和Pb（II）更高的偏好。此外，对于每种官能化的二氧化硅纳米颗粒，金属离子螯合的水平存在差异。每个官能化二氧化硅纳米颗粒表面的金属螯合程度的这些差异通过在附着到表面时硫醇盐/羧酸盐比率的差异和基于表面上硫醇基团的取向的空间原因来解释。当通过酰胺键形成连接时，o-TSA-[二氧化硅]中的硫醇盐位点将面向二氧化硅表面，而对于p-TSA-[二氧化硅]，硫醇盐位点预期指向外部并远离二氧化硅表面。在比较MMSA-[二氧化硅]与DMSA-[二氧化硅]时，硫醇盐/羧酸盐比率从DMSA-[二氧化硅]中的2/1降低到MMSA-[二氧化硅]中的1/1（假设在每种情况下经由一个酰胺键连接）。这种增加硫醇盐与羧酸盐的比率的效果被认为是在对Hg（II）超过Cd（II）和Pb（II）的选择性增强中起作用。
In order to gain additional insight into mercury selectivity with nano-sized DMSA-[silica], we investigated a series of ligands related to DMSA, these are: monomercaptosuccinic acid; MMSA, 2-mercapto-4-methyl-5-thiazoleacetic acid; MCT, ortho-thiosalicylic acid; o-TSA and para-thiosalicylic acid; p-TSA. The MMSA chelate is structurally similar to DMSA except that it has only one thiol group. The chelates o-TSA and p-TSA each have one thiol and one carboxylic acid group. MCT includes neutral S and N atoms in close proximity to the thiolate binding site. MCT, o-TSA and p-TSA resemble each other in having equal numbers of carboxylic acid and thiol groups and formation of amide bonds with the linker on silica is expected to eliminate the carboxylate binding sites, making thiolates the only binding sites for Hg(II), Cd(II), and Pb(II) metals ions in the nano-sized; MMSA-[silica], MCT-[silica], o-TSA-[silica], and p-TSA-[silica]. Each of the nano-sized MMSA-[silica], MCT-[silica], o-TSA-[silica], and p-TSA-[silica], show a higher preference for Hg(II) over Cd(II) and Pb(II) compared to the same free chelates in solution, respectively. In addition, there are differences in the level of metal ion chelation for each functionalized silica nanoparticle. These differences in the degree of metal chelation for each functionalized silica nanoparticles surface are explained by the difference in thiolate/carboxylate ratio upon attachment to the surface and on steric reasons based on the orientation of the thiol groups on the surface. When attached via amide bond formation, the thiolate site in o-TSA-[silica] will face towards the silica surface, while for p-TSA-[silica], the thiolate site is expected to be pointed outwards and away from the silica surface. In comparing MMSA-[silica] to DMSA-[silica], the thiolate/carboxylate ratio decreases from 2/1 in DMSA-[silica] to 1/1 in MMSA-[silica] (assuming attachment via one amide bond in each case). This effect of increasing the ratio of thiolate to carboxylate upon attachment to the surface is believed to play a role in the selectivity enhancement towards Hg(II) over Cd(II) and Pb(II).