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Progress reports

Metal-Aid fellows will provide semi-annual progress reports detailing their research to date. As the reports become available, they will be posted here.  See the side nav bar for reports by semester.

 

 

 

 

 

 

 

 

 

Semester 1

First Progress Reports

ESR 1 Marco Mangayayam: University of Copenhagen

Green rust minerals (GR) consist of Fe2+-Fe3+ hydroxide sheets that sandwich interlayer anions, water, and sometimes monovalent cations. Synthesis protocols for a suite of GR types via oxidation-precipitation of Fe2+ have been established and the synthesised GRs have been characterised with a suite of techniques. Initial results show that GR size and morphology as well as its reactivity with chlorinated solvents is substantially modified by changing interlayer anions and/or cation composition in the hydroxide layer. Short and long-term experiments have been set up to quantify the reduction of several environmentally relevant chlorinated pollutants with the various GR types (ie. tetrachloroethylene, cis-dichloroethylene, carbon tetrachloride).

ESR2 Sandra Navaz Rubio: GFZ

During this first semester I finished the first draft of a literature review and started with the co-precipitation synthesis of green rust sulphate in the presence of toxic metals (Cu, Ni and Zn). Structural properties of the resulting samples have been characterized using Powder X-ray diffraction and Raman spectroscopy. Changes in composition have been analyzed using SEM-EDX while ICP-OES analyses of the fate of the metals is ongoing. The preliminary XRD results suggest that these metals might be incorporated into the octahedral layers of the green rust structure, however, further research must be done to determine the incorporation mechanism and the extent of substitution that can be achieved.

ESR 3 Karen Maria Dietmann: University of Salamanca

Following an intense literature research about the synthesis of Layered Double Hydroxides (LDH) and their potential to remediate chlorinated solvents as well as heavy metals, the best possible candidates have been selected, synthesised and characterised for further research. Thereby, the composition of refined LDHs is based on that of already known and well researched LDHs. Different non-contaminant organic components have been used to change the hydrophobic state of the interlayer of the refined Layered Double Hydroxides. By doing so, their potential to remediate chlorinated solvents from groundwater and soil is enhanced. Currently, experiments are conducted to evaluate the mineral phase, which shows the best ability to retain chlorinated solvents from different aqueous media.

This picture gives insight into the synthesis of the synthesized Layered Double Hydroxides corresponding to the hydrotalcite-group. Depicted is the experimental setup for the reproducible synthesis of the selected phases, which has been conducted by coprecipitation under supersaturated conditions. In this procedure, a mixed solution of the metal cations magnesium and aluminium, is slowly added into a reaction vessel containing a solution of the selected anion together with a magnetic stirrer. The reaction vessel is then placed on a magnetic stirring plate to ensure the constant homogenisation of the mixed solution. As the addition of the metal cations leads to a decreasing of the pH value in the reaction vessel, a 1 molar solution of sodium hydroxide NaOH is dropwise added using a pH meter. Once the pH electrode log a pH value below the limit value the basic NaOH-solution is continuously added until reaching the target value of 9. The addition of the basic solution is then stopped automatically. As a result of this the pH value can be maintained constant within a range of ± 0.2. During the synthesis nitrogen is continuously bubbled into the reaction vessel to avoid any contamination by atmospheric carbon dioxide. Additionally, the beaker glass is closed with Parafilm (Bemis) to maintain a nitrogen atmosphere within the reaction vessel.

ESR 4 Weichao Sun: University of Copenhagen

Through our calculations, we found that all Fe ions might be in 3d6 (Fe2+) or 3d5 (Fe3+) high-spin configurations, this is also consistent with the high-spin occupation of the 3d orbitals for most iron oxides. Moreover, our calculations predict that in the single layered green rust, there are two kinds of iron ions, iron ions in the middle and on the edge of structure are different from each other. And for the single layered green rust, the charge is distributed on the surface unevenly.

ESR 7: Jeffrey Paolo Perez: GFZ

For my PhD project, I aim to examine and elucidate the interactions of GR with various metal contaminants in groundwaters. Based on the survey of literature that I did, I found that most of the GR studies focused on its reductive properties and its interactions with redox-active metals. Hence, I started investigating the sorptive properties of GRSO4. This will allow us to derive new data about surface interactions between freshly-precipitated GRSO4 and metal contaminants. Herein, I focused on the interaction of GRSO4 with arsenic species As(III) and As(V). I determined the effects of variable metal concentrations, ionic strength, pH and adsorbent loading have on GR and evaluate the performance of GRSO4 as an effective metal adsorption material. My goal is to evaluate the stability and recyclability of a GRSO4 adsorbent, and its ability to reduce within a short time metals in groundwaters below environmental standard limits.

To gain more insights into the reactions controlling the processes of GR interactions with contaminants, I will combine various in situ experiments and characterization methods to elucidate the structural changes and mechanisms in the GR pathways. I went to the Diamond Light Source, UK together with synchrotron specialists from our research group last February 10-13, 2017. By observing the formation pathway of delafossite, whose intermediate product is GRSO4, I learned about the set-up needed for conducting in situ and time-resolved scattering and diffraction experiments. This will help me in planning and applying for my own synchrotron beamtime proposal on October 2017.

In addition, I have been accepted to the upcoming “To.Sca.lake 2.0: Total Scattering for Nanotechnology on the Como Lake” summer school on May 29 to June 2, 2017 at Lake Como School of Advanced Studies, Como, Italy. The knowledge that I will gain in this course will be highly beneficial for my project, as it will help me better understand how total scattering can be used to quantify interactions between groundwater contaminants and GR materials at the nano-scale.

ESR 8 Flavia Digiacomo

Several studies* were dedicated to the dechlorination process of chlorinated solvents by green rusts in anaerobic conditions, essentially the sulphate GR(SO42-) and the chloride form of green rust GR(Cl-). Little is known about the role and the kinetic of the carbonate-containing green rust, GR(CO32-), in this kind of reactions. Laboratory experimental results suggest that GR(CO32-), which was synthesized by aerial oxidation of Fe(OH)2, is not stable in anoxic condition. It transformed within some days into a mixture of green rust carbonate and siderite.The questions are:

• Is GR(CO32-) more reactive than the other green rusts which contain in their interlayer different type of anion?

• Is GR(CO32-) able to reduce the chlorinated solvents within one day?

• Are the decay products of GR(CO32-) able to reduce the chlorinated solvents?

• If yes, which are the end-products after reaction with chlorinated solvents?

* Erbs et al. 1998; Lee and Batchelor 2002; Maithreepala and Doong 2005; Choi et al. 2007

ESR 9 Andrew Thomas: KIT

The aqueous Cr (VI) in these experiments was completely oxidized by green rust. Full transformation of green rust resulting from oxidation by Cr (VI) initially produced a Cr (III)-substituted goethite that destabilized to a product consisting primarily of Cr (III) substituted ferrihydrite after 7 days. Identification of Cr (III) bearing phases will not be possible until Cr (III)-bearing Fe (III) oxide reference standards are synthesized.

ESR 10 Shikhar Nilabh: Amphos 21

This period has been intended to start implementing multiphase fluid transport formulation in COMSOL Multiphysics software. I have started with some benchmarking of simple formulation. I modelled the Buckley Leverett problem and McWorther problem with the help of repository models. However, my main accomplishment is the modeling of Kueper problem in Comsol and matching it with the benchmark model of Olaf Kolditz. Moreover, I also tried to model three phase flow of groundwater, air and DNAPL, and now this is still in progress. .

ESR 11 Tobias Linke: University of Iceland

After an initial literature research, the main objective was to map out the stabilities of the different iron mineral phases, especiaily green rust, under natural conditions and with special focus on Iceland. This is done by modelling the stability of mineral phases and aqueous species with PhreeqC. Especially the change of pH and redox conditions (Eh) as well as the initial iron concentration are considered. Together with other data (national soil map, satellite images etc.) this is used to preselect a further field site for sampling of soil samples as cores as well as soil water. The samples will be analysed regarding their mineral content, their elemental composition and their iron speciation.PhreeqC is also used to calculate the impact of the iron phases conceming metal transport in aqueous media. The uptake and release of heavy metals by iron phases is calculated along a redox gradient simulating the transfer of the minerals from inside the peat area to a drainage system or natural rivers and finally to the ocean. In addition, the impact of metal adsorption to organic soilmaterial (e.g. humic acids) is investigated by modelling. A field site was selected during an initial trip to potential work areas and permissions as well as samples were collected.

fThe photo on the left shows a typical man-made ditch which is built to drain the peat areas in Iceland. Because the cumulative length of all ditches in Iceland is around 35,000 km, it is important to understand their impact on the soil chemistry and mineralogy. The ditches contain high amounts of red particles that are assumed to be iron-oxyhydroxide particles. During an initial field trip samples were collected and first analyses were performed (see lower right photo) to gain an insight into the chemistry of the ditches. In addition to the red precipitates, “oily films” were observed (see upper right photo) on some water surfaces that need further investigations. Based on this observations and already existing data, computer models were realised to predict the chemical reactions in the water phase.

The PhreeqC program, in conjuction with the WATEQ4F database, has been used to model the potential of hydrous ferric oxides (ferrihydrite) to adsorb/desorb metals and other anions along oxidation and salinity gradients. Some of the results are presented in the diagram below. The table on the right shows the initial composition of a selected soil water sample under reduced conditions with a high iron content. In the figure, the concentrations of selected elements are normalized to 100 % and are shown under the first step marked with “red” (reduced conditions). After exposing the soil water to air (second step: “oxid”) and oxidizing the Fe2+ to Fe3+, ferrihydrite is formed, which takes up most of the elements by surface adsorption. This process could occur by natural or artificial draining of soils. According to the model, the precipitation of ferrihydrite leads to the near complete adsorption of As, Cu, P and Pb and then, in descending order, Zn (85%), Cd, Ni and Mn (18%).

In the second part of the model, the release of the adsorbed elements is shown by mixing the oxidised solution with increasing amounts of seawater. When the ferrihydrite enters the ocean, some of these metals will be immediately released to the coastal waters, though As and Pb are last after mixing more than 1:100,000 with seawater.

This figure shows that high amounts of different elements could be adsorbed to iron phases by oxidation and become removed from the soil. Furthermore, these elements become release during mixing with seawater if they are transported to the ocean as particles.

ESR 12 Markus Reischer: Niras

The critical data compilation is complete, allowing construction of a hydrogeological model. This model will be shared among the METAL-AID partners (in particular AMPHOS21), so that computer simulations can be performed with identical basis.

ESR 13 Adrian Schiefler: Capital Region of Denmark

A first set of field soil samples have been investigated by X-ray computed tomography to obtain a better understanding of the pore structure (porosity/permeability/mineralogy). The X-ray tomography setup is currently developed further to allow for in-situ and time-resolved monitoring of particle transport and aggregation behaviour under flow through artificial columns (beads pack) and through natural soil samples. Also, microcosm batch experiments were conducted to investigate biotic TCE degradation by microbial communities present in groundwater collected at the field site. The cultivated bacteria were able to degrade TCE to cisDCE but no further. Genomic characterization of the microbial communities is planned. Batch experiments to investigate the impact of Green Rust on microbial activity will follow.

ESR 14 Virginia Alonso de Linaje: AECOM/URS

I started my PhD in November 2016. During the first 6 months I went through extensive literature review on nanoparticle agents for soil remediation and chlorinated organic pollutants characteristics to determine research gaps that need to be filled. I also learnt about the pilot-test site, AECOM field procedures / Standard Operating Procedures (SOPs), business model, environmental business, and remediation project development. I had the opportunity to gain experience on safety and systematic procedures for field data collection and geochemical data visualization and interpretation.

Semester 2

 

ESR 1 Marco Mangayayam: University of Copenhagen

Modified green rusts (GR) have been synthesized by changing the cationic species in its brucite-like layer structure or by altering the host interlayer anion with organic molecules. Synthesis parameters for these modifications have been optimized from previous GR recipes via oxidation-precipitation method. The inorganic modification showed interesting features, which led to drastic change in its reactivity in comparison to the pristine GRs. Organic modification showed GR like structure, implying the success of the molecule intercalation in the interlayer. Further confirmation by suites of techniques is needed to affirm such results.In addition, sulfidized-zero valent iron has shown to be promising for field remediation and therefore current focus lies on streamlining synthesis of such particle as well as their reactivity for chlorinated solvent degradation.

The figure below shows the SEM image of hierarchical structure of zero valent iron modified with sulphide coating totest for reduction of chlorinated solvents.

ESR2 Sandra Navaz Rubio: GFZ

Small changes in cell parameteres observed in XRD patterns contribute to a reduction of the cell volume with increasing Ni concentration;  This might be evidence that Ni is replacing Fe(II) sites.  Furthermore, by imaging samples co-preceipitated with high Ni concentration in the TEM, I observed that they appear to have irregular edges and some "amorphous" areas which might be an effect of the incorporation of Ni.  However, a deepter study of this is necessary to ensure that it is not an artifact caused by beam damage.

ESR 3 Karen Maria Dietmann: University of Salamanca

In the past months my daily lab work was focused on the question if previously synthesised LDHs, which are related to the hydrotalcite-group, are effective regarding the remediation of chlorinated solvents from aqueous media. Additionally, I intensified my knowledge about different characterisation methods by attending various workshops.Sharing my latest results with other researchers at the 27th Goldschmidt conference, which was held in Paris from August 13-18, gave me new inputs and ideas to clarify some of my most urgent questions that came to my mind during the daily work in lab.

ESR 4 Weichao Sun: University of Copenhagen

We calculated the single layer green rust structures with different Fe(II)/Fe(III) ratios and calculated the population. We assumed all the iron atoms are in high spin multiplicities, which means the Fe(II) has four unpaired electrons and Fe(III) has five unpaired electrons. In the structures, there are 19 iron atoms that I defined into three kinds: centre, inner and outer iron atoms. We found that in all the structures except with the ratios are 1/18 and 2/17, the outer iron atoms have more unpaired electrons, which means they are more likely supposed to be Fe(III), and have high reduction potential; the inner iron atoms have less unpaired electrons which are more likely supposed to be Fe(II). And all the centre iron atoms have least unpaired electrons. For all the structures, the unpaired electron of inner irons atoms change more with ratios changing. We can also clearly see that there are big gaps between the numbers of unpaired electrons of outer and inner iron atoms. All the results could indicate that for the single layer green rust, the redox reaction sites are more likely to be on centre parts of the structures.

ESR 5 Lisa Füllenbach: University College London

I was recruited to the Metal-Aid project on 1 September 2017.  During the coming reporting period, I will continue with literature research and work on batch experiments.  I will also attend the third meeting of the Metal-Aid project in Kaprun, Austria.  In the spring term of 2018, I will be enrolled as a teaching assistan for the Earth Sciences Department at UCL (courses and field trips).

ESR 6 Fieke Mulders: University College London

I was recruited to the Metal-Aid project on 1 July 2017.  Over the first months of my project I will focus on laboratory work: setting up experiments and developing those that are running.  The aim is to get some first results which could steer me in the right direction.  Furthermore, I would like to start with some outreach activities as well as some course work.  Additionally, I will attend project meetings.

ESR 7: Jeffrey Paolo Perez: GFZ

During the second reporting period, I investigated the interaction of green rust sulfate (GRSO4) with arsenic (As) species using batch adsorption experiments.  I examined various parameters to determine their influence on the adsoprtion of As on GR SO4.  Our results suggest that pH and ionic strength, expecially the presence of common groundwater species such as Mg2+ and PO43- affects As removal efficiency.  More importantly, GRSO4 is stable and can adsorb large amounts of As which exceeds the maxiumum uptake of common iron (oxyhydr)oxides present (near) subsurface environments. These results highlight the importance of GR mineral phases in the sequestration of As in anoxic groundwaters.

ESR 8 Flavia Digiacomo

The transport mechanism of green rusts (GRs) reactants was studied in water saturated column experiments. Column tests are among the main tools to a better understanding of the behaviour of the abovementioned particles as soon as they are injected in porous media. The mobility of GR particles was studied in a series of laboratory water-saturated column experiments, samples were collected each minute in order to build a conventional breakthrough curve (plot of relative concentration of a given substance versus time); the relative concentration (Crelative) is defined as the ratio of the actual concentration (C) to the source concentration (C0): Crelative = C/C0.

The figure below shows schematically how column experiments are carried out: injection of the suspension (or contaminant solution) using a peristaltic pump (flow rate 1,5 mL/min); collection each minute of the samples in small centrifuge tubes (1,5 mL); analysis of the outlet samples using UV-VIS spectrometer and ICP-OES and interpretation of the data using breakthrough curves (concentration versus time).

ESR 9 Andrew Thomas: KIT

Due to the results obtained from the kinetics experiments and further EXAFS analysis with a more complete set of reference standards, I now have a sufficiently complete understanding of the processes taking place in my experiments to publish my results and begin experiments to determine and optimize the efficacies of these particles in the field.

ESR 10 Shikhar Nilabh: Amphos 21

The field study in Copenhagen provided me with new insights to make multiphase and transport models accounting for the fluid and contaminant flow in the subsurface. I pivoted my work to include the fracture geometry in the subsurface. The literature review and case studies helped me develop dual porosity models accounting for transport in fracture and diffusion in Matrix. The model was further extended to study the back-diffusion phenomenon. After verifying these models, it was upscaled to the field-scale dimension. Currently I am focusing on developing multiphase multicomponent flow in the subsurface.

ESR 11 Tobias Linke: University of Iceland

During the second time period of this PhD project, different water and solid samples from a field site in Iceland were collected and analysed at the University of Iceland as well as at the University of Copenhagen. The conducted analysis gave first insights to the chemical composition and the mineral content of the different natural samples. The data were interpreted with a focus on natural iron cycling and phase transformation. Based on this work, the experiments to be conducted in the near future were planned. To gain additional knowledge of possible analytical and modelling techniques, different training workshops were attended. The first results of the work were presented at the international geochemical conference Goldschmidt 2017.

For more information about work performed during this reporting period, please click here.

ESR 12 Markus Reischer: Niras

I followed two lines of work. In one line, I set up a 3D flow and transport model using Modflow and MT3DMS with GMS as the graphical user interface. Due to current low concentration of contaminants in the groundwater at the test site, the consortium intends to shut down the pump and treat facility, that currently operates to contain the contamination to increase the concentration again for later experiments. Thus, I used my 3D flow and transport model to evaluate the safety of a pump shutdown. Results show that the pumping can be stopped for 1 year at least. In the second line of work, I tested the optical image profiler (OIP) for the detection of fluorescent tracers. This device was originally made for detection of hydrocarbons. I tested three different versions of the probe, that are optimised for different light wavelengths. Standard dye tracers could be detected with all probes. However, the sensitivity of the three types of probes varied based on the fluorescent tracer. The first field testing with Eosin injection in the groundwater showed that the tracer could be confidently detected. Further laboratory experiments are now in progress.

ESR 13 Adrian Schiefler: Capital Region of Denmark

I received training in both the procedure of PCR, the informatics to evaluate microbial community structure and x-ray tomography data analysis and finite element modelling. I learned about iron oxide synthesis and characterisation by various techniques. I made some first experiments in microbiology to progress the experimental setup for my intended studies. I was lucky to visit the Spring8 synchrotron research facility in Japan and have a first try to track Green Rust particle transport. However the particles seem to show too little absorption and mobility during my experiments to track them. I visited the Aquaconsoil conference in Lyon where I gave a presentation, made valuable contacts regarding all aspects of my PhD plan and met again with the ESRs of the Remediate ITN. And if lucky, I will be almost done with collecting my ECTS!

ESR 14 Virginia Alonso de Linaje: AECOM/URS

During the second semester, I gathered field data to develop a regional groundwater model for the pilot test site. As part of my secondment at the University of Salamanca I synthesized and characterized two types of layered double hydroxides (LDHs) with surfactants in the interlayer that I will use to adsorb chlorinated hydrocarbons from the groundwater.

Figure 1. Virginia during a field campaign collecting data to be used at the laboratory and to feed the groundwater model.
Figure 2. Laboratory set up for layered doubles hydroxides synthesis. A solution of Mg(NO3)2 and Al (NO3)3 is added at a low rate of 1 ml/min into a solution containing a known concentration of organics to be intercalated in the LDH interlayer. The pH is maintained at 9±0.5 by a controlled addition of NaOH. During the process the solution is stirred and nitrogen is burbled in the vessel. Organo-LDHs are aged for 24 h under nitrogen burbling.
Figure 3. Pulverized organo-LDHs. After drying during at least 72 h LDHs are powdered and stored in plastic bottles before using.

Semester 3

Available March 2018

Semester 4

Available September 2018

Semester 5

Available March 2019

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