Current Projects
The curious case of clay minerals – how these overlooked minerals control redox reactions on Earth (09/2022 ― 08/2023; funded by the Alexander von Humboldt Foundation through a Humboldt Research Fellowship for Experienced Researchers)
Clay minerals have long been regarded as mostly unreactive but are emerging as potentially important redox-active minerals in natural environments. Intriguingly, their interaction with the naturally abundant reductant Fe(II) leads to the formation of transient, yet highly reactive mineral species capable of degrading recalcitrant contaminants. This project will determine the identity of these reactive mineral intermediates (RMIs), which is key to understanding their role in many of Earth’s crucial element cycles, as well as nutrient availability, and contaminant degradation. Due to their transient and highly reactive nature, RMIs are challenging to characterize and our preliminary results further suggest that the RMIs are amorphous or nano-crystalline, present in low abundance and frequently made up of particles of very small sizes (nanometer range). Here, we will use an alternative approach based on the isotope-specificity of Mössbauer spectroscopy to selectively study either the clay mineral Fe or the Fe-containing RMIs. We will combine this with high-resolution transmission electron microscopy (HR- TEM) equipped with analytical tools that cannot just identify but fully characterize these nano-phases, and with the atomic pair distribution function (PDF) method to resolve this conundrum. This project’s results will underpin the needed process understanding that will significantly enhance our ability to assess and understand RMIs’ contribution to element cycling and contaminant degradation in natural environments – and hence how clay minerals control redox reactions on Earth.
This project is hosted by Prof Liane G. Benning at the German Research Centre for Geosciences (GFZ).
Novel clay mineral-based technologies for the treatment of per- and polyfluo- roalkyl substances-impacted matrices (NSERC Alliance Grant; 06/2022 ― 05/2024)
Per- and polyfluoroalkyl substances (PFAS) are among the main contaminants of concern at thousands of contaminated sites in Canada and the United States and also among the most challenging pollutants to remediate. Efficient and sustainable remediation technologies are urgently needed for mobile PFAS and those retained by soils, rocks or solid surfaces. We propose to apply a systemic view to the PFAS contamination problem from source to plume and suggest developing a modular treatment train based on natural and modified clay minerals. For the treatment train, we will develop innovative, cost-effective, and sustainable approaches for in-situ and ex-situ treatment of PFAS-impacted ground- and surface water, soil, and sediment. Our objectives are (1) to develop a new treatment process that uses reactive and self-regenerating Fe-containing clay minerals for in-situ remediation of contaminant source zones via radical-accelerated PFAS degradation, and (2) to further develop and evaluate modified bentonite adsorbents for the removal of mobile/mobilized PFASs in challenging water matrices. The team will build upon preliminary data and years of experience in PFAS and clay mineral research to develop the mechanistic process understanding for future applications of clay minerals for modular in-situ and ex-situ treatment of PFAS. Our treatment train targets the source of contamination and will therefore provide a clear endpoint for clean-up operations, which enables cost predictions and environmental impact assessments. When practical and sustainable PFAS treatment solutions are identified and well developed, there will be thousands of sites where the solutions could be applied. These upcoming remediation projects will energize Canada’s economy through engineering, technology development, environmental remediation and water/wastewater treatment market. Federal government departments, municipalities and private corporations most affected by the PFAS crisis to may redirect investments currently used to fund inefficient PFAS treatments to business initiatives that would greatly benefit to the Canadian economy.
Lead Investigator: Prof Jinxia Liu (McGill University); Collaborators: Stefano Marconetto (WSP Global Inc.), Michael Donovan (CETCO, Minerals Technologies Inc.)
Cataclastic hydrogen and oxidant production in the deep biosphere: uncover- ing the ancient role of microbial antioxidant enzymes (CERBERUS) (NERC funded project; 05/2022 ― 04/2025)
This project will ascertain how mechanochemical reactions, that can occur along tectonically driven faults and fracture zones, can generate hydrogen gas and oxidants from water to support the hot, subsurface biosphere, both today and in the deep geological past. More information on the CERBERUS website.
Lead Investigator: Dr Jon Telling; Collaborators: Prof Neil Gray; Prof Jan Kaiser (University of East Anglia)
Understanding Arsenic removal processes: passive treatment systems as proxies for natural environments (NERC IAPETUS2 funded PhD project; 10/2021 ― present)
We recently found that As removal occurred in a compost-based passive treatment system for mine-water, which may be a potential low-cost and zero-energy treatment for As-contaminated irrigation water. However, the process(es) leading to this unexpected removal are currently unclear but may be relevant to other passive treatment systems (e.g. sand or zero-valent iron-based filters), and/or occur in natural environments such as soils. This project will investigate the fundamental processes of As removal in these passive treatment systems, as case studies for natural attenuation processes.
Co-investigators: Prof Adam Jarvis; Prof Cindy Smith (University of Glasgow); supported by the Coal Authority/Environment Agency
Developing a quantitative framework for predicting abiotic attenuation under natural and transitional site management scenarios (in collaboration with Paul Tratnyek and Richard Johnson (Oregon Health & Science University) and Michelle Scherer, Drew Latta, and Tim Mattes (University of Iowa), SERDP funded project; 09/2020 ― 09/2023)
Current conceptual site models do not adequately include abiotic natural attenuation of chlorinated solvents, as this pathway is difficult to characterize and contributing processes have only recently been recognized. The main objective of this project is develop a quantitative framework for characterizing site geochemistry and assessing site management scenarios with respect to their potential for natural abiotic attenuation, including changes in site conditions. Detailed project description
Harnessing microbially mediated redox processes for sustainable water treatment (EPSRC funded PhD project; 10/2019 ― present)
Providing clean water for all remains one of the main challenges for humanity and thus is one of the UN’s Sustainable Development Goals (SDG6). In this project, we will address this challenge by investigating the potential of a recently discovered process involving natural sedimentary minerals to sustainably treat water. The process relies on the production of hydroxyl radicals to degrade organic pollutants during the reaction of reduced iron in clay minerals with oxygen and the sustainable regeneration of clay mineral reduced iron by microbes under anoxic conditions. However, it is currently unknown whether treatment efficiency can be maintained over several cycles of use and re-generation under realistic environmental conditions. Using mesocosm experiments, we will evaluate the sustainability of the treatment and regeneration processes; monitor the evolution and efficiency of the microbial communities driving clay mineral reactivity regeneration (via DNA/RNA metabarcoding); and examine the suitability of ecological indicators and analytical techniques as novel, low-cost tools for performance monitoring. This interdisciplinary project will provide the proof of concept that a low energy, low input (waste) water treatment system harnessing microbially mediated redox processes of iron-bearing clay minerals can be operated sustainably and at scale. The overall aim is to demonstrate a feasible water treatment approach for high, middle, and low-income countries alike.
Co-investigator: Dr James Kitson
Providing the last piece of the puzzle: Completing our understanding of the unusual redox buffer behavior of clay minerals (funded through Eawag discretionary funds; 07/2019 ― present)
The characterization of redox properties of clay minerals through research initiated at Eawag has significantly advanced our understanding of nutrient cycling, trace element mobility, and organic pollutant transformation in subsurface environments. Such information has also become practically useful, for example, for expert consulting on the assessment of host rocks and buffer materials for the storage of radioactive wastes. The clay minerals’ unique ability to buffer redox reactions over an unusually large range of environmental conditions was hypothesized to originate from reversible changes in redox state of iron in their octahedral sheet, yet the role of iron in the tetrahedral sheets remained elusive. Because synthetic clay minerals with well-defined iron coordination have recently become available, we propose to investigate their redox properties with a combination of electrochemical and spectroscopic methods to complete our understanding of the redox buffering by iron-containing minerals in soils and groundwaters.
Lead investigator: Dr Thomas Hofstetter
Collaborators: Fabien Baron, Sabine Petit, Eric Ferrage (University of Poitiers); Jagannath Biswakarma (University of Bristol); Carolyn Pearce, Michel Sassi, Kevin Rosso (PNNL); Meret Aeppli (EPFL); Andreas Voegelin (Eawag); Michael Sander (ETH Zurich)
Completed Projects
Enhancing analytical capabilities in soils for low-carbon technologies (11/2020 ― 10/2021; funded through the White Rose Collaboration Fund)
The aim of this project is to combine different analytical microscopy and spectroscopy techniques to accurately identify and monitor Fe and Al co-ordination and speciation in soils at the micro- to nano-scale. The advances made will help tackle outstanding questions around soils’ role in low-carbon technologies.
Lead investigator: Alastair Marsh (University of Leeds); all team members and details on the project
Advancing Circular Economy (ACE) Research and Development Demonstrator project (09/2020 ― 01/2022)
This innovation demonstrator project is co-funded by the North of Tyne Combined Authority and Proctor & Gamble and brings together collaborators from Proctor & Gamble’s Newcastle Innovation Centre, Newcastle University, Northumbria University, Prozomix Ltd., the Centre for Process Innovation, and the Innovation SuperNetwork. The project will realize three Demonstrators and we will be involved in Demonstrator 2: Innovation for Water Scarcity. Find out more about the other demonstrators and the entire project.
Assessing the sustainability of Fe-bearing clay mineral redox reactions for application in engineered systems (EPSRC funded PhD project; 10/2017 ― 06/2022)
The quality of surface and groundwater is strongly influenced by redox reactions of iron-bearing minerals, which transform contaminants and nutrients. Iron-bearing clay minerals are particularly important because they are thought to be a renewable source of reduction equivalents in the environment. In this project, we will test the validity of this paradigm and expand current knowledge from closed systems to more realistic, flow-through conditions. Specifically, we will investigate aspects of reversibility of clay mineral redox reactions; the effect of redox cycling on clay mineral stability and reactivity; and differences between chemical, microbial, and biologically mediated clay mineral iron reduction. We will complement our experimental work with quantitative modeling of the processes involved. The results of this project will aid in designing effective (natural) remediation strategies as well as engineered water systems such as aquifer storage and recovery.
Antibacterial Clay Therapy (sponsored by the Institute of Advanced Study, Durham University; 09/2019 ― 01/2020)
Antimicrobial resistance is a global concern requiring innovative and lateral approaches to combat the threat to human health. New antimicrobial agents and materials are urgently needed to tackle increasingly drug resistant pathogens. For centuries, clay minerals have been employed in traditional medicine, either topically or by ingestion. Recent studies have verified that clays do possess unique antibacterial properties that offer considerable health benefits. The approach to this project aims to merge empirical studies on the constituents and antibacterial properties of therapeutic clays, while also considering political, social and cultural contexts that may inform future medical applications.
As a starting point, we will evaluate clay from the Baku region of Azerbijan as an antibacterial agent with potential for the treatment of wound infections. The structure and composition of this clay will be specifically defined and its antibacterial efficacy assessed against representative bacterial species. As an integral part of the project, we will commence a broader, humanities-driven approach to investigate the poorly characterised usage of clays in the treatment of infections. There are many questions surrounding the different ways that clays are harnessed as therapies, for what types of infection and in what kinds of social interactions.
Lead investigators: Dr Gary J. Sharples, Dr Kim Jamie (Durham University)
Biologically Mediated Abiotic Degradation of Chlorinated Ethenes: A New Conceptual Framework (in collaboration with Michelle Scherer, Drew Latta, and David Cwiertny (University of Iowa), and Rula Deeb and Deepa Ghandi (Geosyntec consultants), SERDP funded project; 10/2015 ― 6/2019)
While biological degradation of PCE and TCE has been studied in some detail, there is still a significant knowledge gap in our understanding of how abiotic processes contribute to the degradation of PCE and TCE. The overall objective of this project is to apply a new conceptual framework based on solid- state mineral chemistry to understand biologically mediated abiotic degradation (BMAD) of PCE and TCE by magnetite, Fe sulfides, and Fe-bearing clays.
This project was awarded ‘SERPD project of the year 2018‘.
From the lab to the real world – redox reactions in complex biogeochemical environments (EPSRC funded PhD project; 10/2014 ― 01/2019)
Contaminant transformation and (bio)availability as well as nutrient cycling are strongly affected by redox reactions of Fe-bearing minerals in subsurface environments. While previous laboratory studies addressed the redox reactivity of individual Fe minerals, a systematic evaluation of the combined reactivity of co-existing Fe minerals is lacking. This project will bridge the knowledge gap between laboratory experiment and natural systems. Various Fe-bearing minerals and representative soil organic components will be combined to simulate the complexity of natural environments. Experiments will range from batch to flow-through experiments and will include solid phase and redox characterization (e.g. reactive probe compounds, ICP-MS, Mössbauer spectroscopy).
Cleaning water with mud: clay minerals producing reactive oxidizing species (EPSRC Bright Ideas Award; 8/2015 ― 10/2017)
We take for granted that high quality drinking water is delivered directly to our home and that the wastewater we produce is treated to a level where it is safe to be released into the environment. Water treatment involves, however, intense inputs in the form of chemicals and energy to transform organic contaminants into a harmless form and to destroy harmful microbes, making water treatment a financially and environmentally costly process. In this project, we explore whether an abundant and low-cost natural material, clay minerals, can sustainably generate reactive oxidizing species for advanced oxidation in water treatment.
Smart reactive sorbents for the removal of emerging contaminants (in collaboration with Wojciech Mrozik, CEG Seed Corn Funding, 11/2015 ― 4/2016)
Emerging contaminants are a growing concern as current drinking water and wastewater treatment facilities are inadequately equipped to completely remove or transform micropollutants. To address this threat to our water resources, we will create and test the performance of new, smart reactive adsorbents (functionalized clay minerals) by combining approaches from two different fields of research. We will enhance the redox reactivity of the cheap and abundant natural material clay minerals and additionally modify them by the modern, environmental friendly chemicals ionic liquids, to deliver a sustainable solution for micropollutant removal from aqueous solutions.