Cleaning water with mud: clay minerals producing reactive oxidizing species

Lead Research Organisation: Newcastle University
Department Name: Sch of Engineering

Abstract

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 the proposed research, we will explore whether an abundant and low-cost natural material, clay minerals, can sustainably generate reactive oxidizing species for advanced oxidation in water treatment. This approach would need no chemical or energy input and would therefore minimize negative environmental impacts as well as make advanced oxidation affordable also for low-income countries.

We suggest that ferrous iron-containing clay minerals can produce a series of reactive oxidizing species during the reaction with oxygen, similar to what is known for dissolved ferrous iron. Using iron in the structure of clay minerals is, however, key to reliable and repeated regeneration of oxidizing reactivity at the site where oxidation is needed and thus to designing a sustainable advanced oxidation process. In this research, we will provide a proof of concept for advanced oxidation based on iron-bearing clay minerals and will specifically investigate
(1) whether ferrous iron-containing clay minerals oxidize contaminants and inactivate microbes in the presence of oxygen;
(2) which reactive oxidizing species is produced during the reaction and whether any species bound to the clay mineral surface are formed, and
(3) how the oxidative reactivity of clay minerals can be sustainably regenerated.

In a first step, we will thus probe for oxidative reactivity in our clay mineral systems by monitoring the oxidation of model organic contaminants and the viability of microbial organisms. Different clay minerals will be screened to determine the effect of clay mineral properties on their oxidative reactivity and to identify the most promising clay mineral for further investigation. To identify which reactive oxidizing species is produced during the reaction, we will then use specific probe compounds that will react with only one of the different reactive oxidizing species that could potentially form. In additional experiments, clay minerals will be separated from the specific probe compounds by means of semipermeable membranes, allowing us to identify whether reactive oxidizing species are bound to the clay mineral surface. The results from these experiments will demonstrate the effectiveness of iron-bearing clay mineral-based advanced oxidation for disinfection and contaminant oxidation. In a last series of experiments, we will assess how we can reliably and repeatedly regenerate the oxidative reactivity of iron-bearing clay minerals. To this end, we will start with batch experiments in which the re-cycling of clay mineral reactivity will be achieved with chemicals and we will then apply the same approach to column experiments. Next, the activity of specific microbes will be used to regenerate the oxidative reactivity of clay minerals and finally only water flow and column saturation will be managed to show how iron-bearing clay minerals can be used for sustainable advanced oxidation.

In this research, we aim to demonstrate that advanced oxidation for water treatment can be implemented using a natural material often referred to as "mud" and how this advanced oxidation process can be managed and applied sustainably for water treatment or soil and sediment remediation. The expected results will illustrate a way forward to identifying new and intrinsically sustainable water treatment processes that could be applied in high-, middle, and low-income countries.

Planned Impact

Access to clean water was identified as one of the UN Global Issues and is a major component of the UN Millennium development goals. In places where water treatment is being carried out, treatment often relies on energy and cost intensive technologies that are therefore not sustainable and have only limited potential for application in low income countries. In the UK, the water industry consumes about 1% of the energy produced in the UK and energy and chemical costs for water and wastewater treatment amount to about 1 billion £ each year.

The proposed project will provide a proof of concept for how to sustainably generate reactive oxidizing species for advanced oxidation in water and wastewater treatment by exploiting the reaction of the natural material Fe-bearing clay minerals with oxygen. Because this novel approach would require neither additional chemicals nor energy, it would help minimize energy consumption, carbon emissions, and chemical costs of water and wastewater treatment. Demonstrating the potential of a natural abundant material to produce reactive oxidizing species may change how and where we look for next generation, sustainable water treatment processes and also suggest a way forward to making advanced oxidation an available and affordable option for developing countries, where most of the roughly 600 million people still lacking access to clean water live. Our research results could therefore potentially benefit the water industry nationally and internationally by reducing energy and chemical costs for water and wastewater treatment as well as water consumers in high, middle, and low-income countries by providing reliable and low cost water services.

Similarly, our approach could change current practices in soil and sediment remediation and transform high-input technologies such as in-situ chemical oxidation into inherently sustainable applications. Reducing chemical and energy inputs in remediation activities will render them more affordable nd thus more likely to happen, which will be beneficial for maintaining or increasing the environmental health of entire ecosystems.

Also other engineered water applications such aquifer recharge or aquifer storage and recovery systems could benefit from this project. Generally, oxygen containing and potentially contaminated surface water is the source water for these applications. Our approach could be used to efficiently clean the water on its way to the aquifer and to prevent release of contaminants from reducing aquifers or sediments. The same mechanisms could also be applied in sustainable urban drainage systems (SUDs) in urban areas, where surface water takes up contaminants during run-off and could be cleaned during its passage within the SUDs. Urban environments would thus be protected from potential surface water contamination and urban population could potentially benefit from re-use and recycling of these and other urban water streams such as grey water with low-cost, sustainable approaches as presented here.

The ubiquity, abundance, and low costs of clay minerals suggest that the here proposed new advanced oxidation process could be applied globally in high, middle, and low-income countries in a diverse range of applications.

Publications

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Description With this award, we intended to explore whether an abundant and low-cost natural material, clay minerals, can sustainably generate reactive oxidizing species for advanced oxidation in water treatment. Our results to date indeed suggest that ferrous iron-containing clay minerals can produce a series of reactive oxidizing species during the reaction with oxygen and that during this reaction contaminants can be oxidized and microbial activity inactivated (objective 1). The yield of reactive oxidizing species varied with the type of ferrous iron-containing clay minerals and in our kinetic analysis we identified several structural parameters that affect the efficiency of the oxidation process (total Fe content, location of structural Fe, clay mineral Fe reduction extent). A comparison between different contaminants indicates that hydroxyl radicals may be the predominant oxidizing species, yet contributions from ferryl iron could not be excluded (objective 2). This proposed dual mode of reactivity could prove useful in real-world applications, where hydroxyl radicals are often quenched by highly abundant natural organic matter. We also successfully implemented the clay mineral oxidation process in a flow through system and were able to demonstrate oxidative reactivity over three consecutive reduction-oxidation cycles.
Exploitation Route One next step is to apply this fundamental reaction to real-world problems such as micropollutant degradation, water treatment or soil and sediment remediation. New collaborations with McGill University (reported in the appropriate section - on sorption and degradation of AFFFs), Durham University (antibacterial and therapeutic potential of natural clay), and within Newcastle University (Case studentship with Thames Water - on Assessing Tertiary Treatment Technologies for Reducing Antibiotic Resistance Genes Abundance and Diversity in Domestic Wastewater Treatment Effluents) are first steps towards this goal.
Sectors Agriculture, Food and Drink,Environment,Other

 
Description Antibacterial Clay Therapy 
Organisation Durham University
Department Institute of Advanced Studies
Country United Kingdom 
Sector Academic/University 
PI Contribution Mössbauer spectroscopy and expertise in the assessment of oxidizing species for redox characterisation of Azerbaijani clays
Collaborator Contribution interdisciplinary team that will look at antibacterial effects of clays, making use of the expertise in geochemistry, microbiology, biochemistry, anthropology, and sociology.
Impact outputs: none so far collaboration is multi-disciplinary: mineralogy, biology, sociology, chemistry, medicine, anthropology, archeology
Start Year 2019
 
Description Contaminant oxidation with intercalated FeOCl 
Organisation East China University of Science and Technology
Country China 
Sector Academic/University 
PI Contribution We analysed a range of intercalated FeOCl samples using our Mössbauer facility. The results have been included in a joint publication, which has been published in the journal ACS Omega (2019). The lead author (Xuejing Yang) and I are planning to extend our collaboration to explore similarities and differences in reactivity of 2D minerals, and will be applying for a RS International Collaboration Award.
Collaborator Contribution The partners developed the synthesis of the intercalated FeOCl material, conducted contamination experiments and analysed most of the data.
Impact Joint publication, published in the journal ACS Omega (Wang J, Tsai, M-C, Lu Z, Li Y, Huang G, Wang H, Liu H, Liao X, Hwang B-J, Neumann A, Yang X. pH-dependent structure-activity relationship of Polyaniline-intercalated FeOCl for heterogeneous Fenton reactions. ACS Omega 2019, 4, 26, 21945-21953. doi:10.1021/acsomega.9b03008)
Start Year 2018
 
Description Interactions of Aqueous Film Forming Foams (AFFFs) with clay mineras 
Organisation McGill University
Country Canada 
Sector Academic/University 
PI Contribution I have provided support in how to design the experiments and we have sent clay minerals samples to the collaborator for initial experiments. Building on my experience, we designed sorption experiments and oxidation experiments similar to those studied in the EPSRC award.
Collaborator Contribution The partners are leading experts in the field of AFFF compound analysis and will thus carry out the experiments and measure both initial AFFF compounds and their potential transformation products (latter in oxidation experiments only). A MSc student has been working on initial experiments and will continue throughout their 2-year program.
Impact No outputs yet; experimental work started January 2018.
Start Year 2017
 
Description Investigating the oxygenation of mackinawite nanoparticles and the resulting oxidizing impact 
Organisation China University of Geosciences
Country China 
Sector Academic/University 
PI Contribution I provided access to lab facilities and essential equipment (Mössbauer spectrometer) for parts of the study. I also provided expertise on how to use the equipment and how to interpret the data.
Collaborator Contribution The partner seconded a PhD student to my lab for 5 months to do initial experiments and learn how to use the equipment mentioned above. Funding for travel, accommodation, and subsistence for the PhD student was provided by the partner.
Impact The results of this collaboration have been written up into a publication; the revised manuscript (second revision) has been submitted to the journal Environmental Science and Technology on 3 March 2020.
Start Year 2016
 
Description Tertiary Treatment Technologies for Reducing Antibiotic Resistance Genes in Wastewater Treatment Effluents 
Organisation Newcastle University
Country United Kingdom 
Sector Academic/University 
PI Contribution Building on my team's findings on inactivating microbes in wastewater effluent, the student investigated a clay mineral based process for its effect on antibiotic resistance genes. My team's know how was put to use to design the laboratory experiments and I am the second supervisor for the student.
Collaborator Contribution The work is part of a CASE studentship (sponsored by Thames Water) and the first supervisor is a leading expert in antibiotic resistance. The collaborator contributes expertise, intellectual input and training of the student in techniques for genetic analysis. The CASE studentship also provides full financial support for the research.
Impact Initial results were presented at the 2nd International Caparica Conference in Antibiotic Resistance (June 2017, Portugal). A more complete set of results was presented at the Research in progress meeting 'Clay minerals in the natural and built environment: formation, chemistry & applications' (May 2019, Newcastle upon Tyne).
Start Year 2016