Iron minerals and their impact on nutrient cycling and contaminant dynamics
Green rust (GR) is a highly reactive, Fe(II)-Fe(III) layered hydroxide mineral that forms in oxygen-limited, Fe2+-rich subsurface environments (e.g., soils, aquifers). GR minerals can effectively sequester toxic elements such as arsenic (As).
Iron-bearing minerals are abundant in the environment where they affect several key (bio)geochemical processes. Because of their high surface area and (redox) reactivity, Fe minerals can control nutrient availability and contaminant mobility in soil and water systems through adsorption or structural incorporation. It is therefore important to understand how they react with nutrients and/or contaminants when they form or transform in nature, and study the geochemical parameters that affect these mineral reactions.
My research interest is focused on the formation and/or transformation of Fe(II)-bearing minerals (e.g., green rust, siderite, vivianite) in oxygen-limited environments and their interaction with nutrients (e.g., P, Si) and/or contaminants (e.g., As, Cr, Pb). Using Fe mineral analogues prepared in the laboratory, I can quantify how these elements affect the structure, morphology, phase stability and reactivity of Fe minerals; and conversely, how Fe minerals impact the speciation and distribution of these elements in the natural environment.
Perez et al. (2021). Arsenic removal from natural groundwater using ‘green rust’: Solid phase stability and contaminant fate. J. Haz. Mat., 401, 123327.
Perez et al. (2021). Arsenic species delay structural ordering during green rust sulfate crystallization from ferrihydrite. Environmental Science: Nano (Advanced Article)
Development of nanomaterials for groundwater remediation
Top: The reactivity of core-shell iron nanoparticles with chlorinated contaminants decreases as it ‘ages’ in groundwater due to corrosion. Bottom left: Mercury (Hg2+) was sequestered at the thiol (-SH) functional groups in the metal organic framework (UiO-66-SH2). Bottom right: Magnetic iron oxide nanoparticles supported on a covalent triazine framework (CTF-1) is an effective sorbent material for the removal of As and Hg species from water.
In addition to (synthetic) minerals, I am also interested in the development and synthesis of nanomaterials for treating heavy metals and chlorinated solvents in water. I have worked on nanoporous materials (MOFs and COFs) for the removal of mercury (Hg2+) species during my MSc research. Through the introduction of functional groups or incorporation of iron nanoparticles, I was able to improve the Hg sorption capacities of the nanoporous materials I have synthesized. I am currently working together with research collaborators to prepare novel functionalized nanoporous materials for metal sequestration/recovery.
I have also been closely involved in the development of sulfidated nanoscale zero-valent iron nanoparticles (S-nZVI) through the Metal-Aid ITN. The S-nZVI material exhibits high reactivity over extended periods in groundwater because the iron sulfide shell protects it against aqueous corrosion. By modifying its shell properties, it was possible to fine tune its selectivity and reactivity for various chlorinated compounds, even in complex contaminant mixtures in natural groundwater (manuscript under review).
Some important resources on environmental geochemistry and nanogeoscience
Hochella, M.F. (2008). Nanogeoscience: From Origins to Cutting-Edge Applications. Elements, 4 (6): 373–379. DOI: 10.2113/gselements.4.6.373. [PDF]
Brown, G.E., Foster A.L., Ostergen, J.D. (1999). Mineral surfaces and bioavailability of heavy metals: a molecular-scale perspective. Proceedings of the National Academy of Sciences, 96(7), 3388-3395. DOI: 10.1073/pnas.96.7.3388. [PDF]