I'm a postdoctoral fellow in the Department of Earth System Science at Stanford Doerr School of Sustainability. I received my Ph.D. from Virginia Tech in Environmental Nanoscience/Geochemistry. My Ph.D. research focused on understanding the role of iron (hydr)oxide nanoparticles in immobilizing contaminants in the environment. Specifically, I examined the impact of oxyanion surface complexes, including phosphate, sulfate, nitrate, and arsenate, on the formation and transformation kinetics of ferrihydrite, a ferric oxyhydroxide nanomineral that is extremely important for elemental cycling in many (bio)geochemical systems. My research also addressed highly reactive and ultra-small ferrihydrite precursors, known as Fe13-like clusters, and their reactivity and transformation behaviors.
I have also earned two MSc degrees in geology and chemistry. The objective of my first MSc degree (University of Tehran, Iran) was to examine natural clay formation and evaluate its potential for retaining other elements, such as rare earth elements. My second MSc degree (Georgia State University, USA) focused on understanding the energetics and thermodynamics of oxyanion adsorption on ferrihydrite.
Honors & Awards
PRISM Baker Fellowship, Stanford University (2022-2023)
Interdisciplinary Graduate Education Fellowship, Virginia Tech (2021-2022)
Interdisciplinary Graduate Education Fellowship, Virginia Tech (2018-2019)
Scott Fendorf, Postdoctoral Faculty Sponsor
Current Research and Scholarly Interests
Natural clays and nanosized metal oxide and hydroxides control the fate and transport of contaminants and nutrients in soils and aqueous environments. Progress in this area will have substantial implications for addressing critical issues facing society related to air and water quality, contaminant transmission, climate change, etc. My research interests are founded on two main pillars: 1) nanoparticle formation and transformation processes and 2) chemical processes governing their reaction with contaminants and nutrients under Earth-surface environmental conditions. My current research investigates the role of soil nanoparticles in the formation and dispersion of hexavalent chromium during and after wildfires.
Oxyanion Surface Complexes Control the Kinetics and Pathway of Ferrihydrite Transformation to Goethite and Hematite.
Environmental science & technology
The rate and pathway of ferrihydrite (Fh) transformation at oxic conditions to more stable products is controlled largely by temperature, pH, and the presence of other ions in the system such as nitrate (NO3-), sulfate (SO42-), and arsenate (AsO43-). Although the mechanism of Fh transformation and oxyanion complexation have been separately studied, the effect of surface complex type and strength on the rate and pathway remains only partly understood. We have developed a kinetic model that describes the effects of surface complex type and strength on Fh transformation to goethite (Gt) and hematite (Hm). Two sets of oxyanion-adsorbed Fh samples were prepared, nonbuffered and buffered, aged at 70 ± 1.5 °C, and then characterized using synchrotron X-ray scattering methods and wet chemical analysis. Kinetic modeling showed a significant decrease in the rate of Fh transformation for oxyanion surface complexes dominated by strong inner-sphere (SO42- and AsO43-) versus weak outer-sphere (NO3-) bonding and the control. The results also showed that the Fh transformation pathway is influenced by the type of surface complex such that with increasing strength of bonding, a smaller fraction of Gt forms compared with Hm. These findings are important for understanding and predicting the role of Fh in controlling the transport and fate of metal and metalloid oxyanions in natural and applied systems.
View details for DOI 10.1021/acs.est.2c04971
View details for PubMedID 36219790
- TRACE AND RARE EARTH ELEMENT DISTRIBUTION AND MOBILITY DURING DIAGENETIC ALTERATION OF VOLCANIC ASH TO BENTONITE IN EASTERN IRANIAN BENTONITE DEPOSITS CLAYS AND CLAY MINERALS 2020; 68 (1): 50-66
Calorimetric study of the influence of aluminum substitution in ferrihydrite on sulfate adsorption and reversibility
JOURNAL OF COLLOID AND INTERFACE SCIENCE
2019; 540: 20-29
Ferrihydrite (Fh) is a nanocrystalline iron (hydr)oxide pervasive in various surface environments. It has high specific surface areas and high density of reactive surface-sites, both of which properties impart a consequential role in determining the fate and transport of environmental nutrients and contaminants. In natural environments, Fh readily reacts with impurities, such as aluminum (Al) and has variable substituted chemical compositions and surface properties. This work examines the effect of aluminum (Al) incorporation (0%, 12% and 24 mol% Al) on the interaction energy of chloride (Cl-) and nitrate (NO3-), and adsorption/desorption of sulfate (SO42-) onto Fh. Microcalorimetry experiments were conducted at pHs 3.0 and 5.6, along with a detailed characterization of all samples. Results showed a significant increase in the energetics of the exothermic peak of NO3- and the endothermic peak of Cl- with increasing Al concentration and decreasing pH values. Furthermore, the exothermic heat of exchange, adsorption, irreversibility and fraction of inner-sphere complexes for sulfate interaction with Fh increased with more Al concentration and acidic pH.
View details for DOI 10.1016/j.jcis.2019.01.001
View details for Web of Science ID 000460710800003
View details for PubMedID 30622055
- Genesis of the Eastern Iranian bentonite deposits APPLIED CLAY SCIENCE 2019; 168: 56-67
- Characterization of Iranian bentonites to be used as pharmaceutical materials APPLIED CLAY SCIENCE 2015; 116: 193-201