Diffusive Gradient in Thin Films (DGT) is a passive sampling technique widely used to monitor for metals in aqueous environment. A DGT sampler often contains two thin layers, namely the diffusion layer and the resin layer. When DGT samplers are deployed, metals in the solution will migrate through the diffusion layer and be taken up by the resin layer. Because the migration of metals through the former layer is strictly via diffusion, it is possible to apply Fick’s law to deduce the concentration of the metal in the solution if the amount of metal accumulated on the resin layer and the deployment time of the sampler are known. The resin layer in DGT samplers is composed of adsorbent particles that are embedded in a polyacrylamide gel. Various types of particle can be used as adsorbent (e.g., chelex-100 resin, iron oxides, titanium dioxide), depending on the targeted metal analyte. In this study, we synthesized sulfhydryl-functionalized silica particles (i.e., SH-SiO2 particles), and tested their use as adsorbent particles in DGT samplers that aim to measure for chalcogenic metals, including Zn and Hg. In particular, the SH-SiO2 particles were synthesized by grafting 3-mercaptopropyltrimethoxysilane on silica gel particles. The SH-SiO­2 particles were then embedded in polyacrylamide gels, and the particle-containing gels (i.e., the resin layer) were exposed to solutions containing a varying amount of Hg and Zn. Preliminary tests indicated that the resin layers were able to quickly remove Zn and Hg from the solution. In addition, extraction of the resin layers with aqua regia showed over 99% recovery of the accumulated Zn and Hg. These results indicated that SH-SiO2-containing gels could be used as resin layers in the DGT sampler. Thus, the resins were then tested as a part of DGT sampler. This test showed that the accumulation of Zn and Hg onto the DGT sampler obeyed the Fick’s law, which should be the case in a properly-designed DGT sampler. Overall, our study showed that the home-made sulfhydryl-functionalized silica particles can be used in DGT passive sampler.

Development of sulfhydryl-functionalized silica particles for use in diffusive gradient in thin-films passive samplers

249th National Meeting (2015)

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