Chapman access only Poster
Iron oxyhydroxides form naturally, often as nanoscale particles, in surface aquatic systems. They represent both a powerful natural attenuation process and a potential remediation strategy for the retention and sequestration of dissolved metals in solution. This is of particular importance in mining environments due to elevated metal concentrations, acid mine drainage, and the health issues that may arise with exposure to potentially toxic metals. Such trace elements are readily transported in water supplies, increasing the geographical extent of their contamination. While metal adsorption processes to mineral surfaces have been extensively studied, desorption processes inform the long-term stability of sorbed metals but are considerably less well studied. The adsorption, and subsequent desorption, of Cu(II) to/from unaggregated iron oxyhydroxide nanoparticles is measured in real time through the use of a copper ion selective electrode (ISE) at time intervals varying from 1 hour to 5 weeks. Adsorption of Cu(II) was immediate and typically complete within one hour, with kinetic adsorption rates generally consistent at 1539.23 ± 163.53 %/min. However, the kinetic desorption rate varied inversely with adsorption time, ranging from 343.41 to 1473.41 %/min. Therefore, the adsorption rate of trials are generally similar whereas the desorption rate decreases as a function of time. Additionally, the percent of Cu(II) retained by the iron oxyhydroxide nanoparticles increases as the adsorption time increases due to longer exposure. Extended X-ray adsorption fine structure (EXAFS) spectroscopy suggests the formation of more stable Cu(II) sorption complexes as the adsorption time increases. As a result, desorption rates of longer trials are noticeably slower than shorter trials because more strongly bound surface complexes are formed, and thus more difficult to desorb. This has implications for the fate and transport of Cu(II) and similar dissolved metals in aquatic systems.
Torossian, Anthony; Jacobs, Jack; and Kim, Christopher S., "Effect of Exposure Time on Cu(II) Adsorption and Retention to Iron Oxyhydroxide Nanoparticles" (2015). Student Research Day Abstracts and Posters. 84.