Functionalized hydrogels for controlled crop nutrient release

Supervisor(s)

Contact Dr Terence P. Kee to discuss this project further informally.

Project description

Feeding our growing world population, currently estimated to be increasing by just over 1% per annum, is a significant and ever more prescient global challenge. Many countries face enormous problems in being able to manage staple crop production with suitable farming practise. Of these key problems, water, nutrient and crop-protection strategies are amongst the most important to address. These are, in turn, most pressing in countries such as India, which is home to 15% of the world’s undernourished population. In order to explore new method of addressing such problems, we will here focus on local, systemic mechanism for managing water retention, nutrient and protection release for staple crops by the use of modified hydrogel composites (MHC’s). Whilst there is a rich literature within this field, our approach is novel as it explores the simultaneous release of multiple key nutrients within a local and controlled environment.

The overall aim of this project is to: develop hydrogel systems based on both inorganic and organic gelators, with the capability of promoting the controlled release of multiple nutrient sources (particularly nitrates, phosphates). In order to achieve this overall aim, the project is divided into a suite of work-packages (WP) each of which has key deliverables. These together will address the overall aim of the project as outlined in the section on Methodology below.

Methodology

Selection of gelator systems to explore

We will examine various different gelator systems for producing hydrogels. Our investigations will include work on organic gelators, especially those that are recognised as being naturally occurring and low toxicity hydrogelators such as guar and gallan gum.

We will also examine mineral or inorganic gelators including silica hydrogels and hydrogel; based on the synthetic clay mineral laponite.

Deliverables: Reasoned selection of hydrogel systems to be explored.

Chemical Functionalisation of Organic Gelators Organic hydrogel systems

These systems, based on guar or gellan gum, have the potential to be covalently modified at the hydroxyl functionalities. We will examine mechanisms to do this by a combination of phosphorylation and hydrolysis to afford terminal phosphate functions. Phosphorylation will be performed using known phosphorylating agents such as amido and/or diamidophosphates.

Preparation and characterisation of functionalised organic hydrogel systems.

Functionalisation of Inorganic Mineral Gelators

The key aspects of functionalisation with the context of the mineral, inorganic gels such as laponites is to exploit the natural electrostatic interactions between clay particles to encapsulate phosphate and nitrate salts between the stacked clay particles. In addition, we will explore the ability of surfactant additives (such as sodium dodecyl sulfate) on stabilising such salts with the hydrogel environment.

Deliverables: Preparation and characterisation of functionalised mineral hydrogel systems.

Examination of Nutrient Release Kinetics Phosphate

Release kinetics will be examined in a controlled reactor space, both using static water sinks and dynamic watercourses. Analytical determination of phosphate will be achieved using a combination of quantitative 31P-NMR spectroscopy and also by fluorescent tagging of phosphate; both techniques having sensitivities in the sub-ppm range. Deliverables: Scope of phosphate and nitrate release kinetics as a function of environmental and hydrogel properties.

Examination of Environment-Responsive Nutrient Release Kinetics

In this work-package, we note the unusual behaviour of laponite clays, where the gel properties change over time as the clay particles organise themselves. We will examine how it may be possible to control the structure/viscosity of the hydrogel by local environmental conditions such as physicochemical changes in pH or presence of chemicals released by a second, composite hydrogel (a guar gel for example). Deliverables: Potential for using remote, environmental triggers for nutrient release from hydrogel systems.

References

1. J. Saltiel, J. W. Bauder, S. Palakovich. Adoption of Sustainable Agricultural Practices: Diffusion, Farm Structure, and Profitability. Rural Sociology (1994), 59, 333-349.

2. I. P. Abrol and Sunita Sangar. Sustaining Indian agriculture – conservation agriculture the way forward. Current Science (2006) 91, 1020-1025.

3. How sustainable farming in India can secure its food for ther future.

4. M. Cassanelli, I. Norton, T. Mills. Role of gellan gum microstructure in freeze drying and rehydration mechanisms. Food Hydrocolloids (2018) 75, 51-61.

5. Ruzicka B. et al. Observation of empty liquids and equilibrium gels in a colloidal clay. Nat. Mater. (2011) 10, 56–60.

Entry requirements

Applications are invited from candidates with or expecting a minimum of a UK upper second class honours degree (2:1), and/or a Master's degree in chemistry, physics or environmental science.

If English is not your first language, you must provide evidence that you meet the University’s minimum English Language requirements.

How to apply

Formal applications for research degree study should be made online through the university's website. Please state clearly in the research information section that the PhD you wish to be considered for ‘Functionalized hydrogels for controlled crop nutrient release’ as well as Dr Terence P. Kee as your proposed supervisor.

We welcome scholarship applications from all suitably-qualified candidates, but UK black and minority ethnic (BME) researchers are currently under-represented in our Postgraduate Research community, and we would therefore particularly encourage applications from UK BME candidates.  All scholarships will be awarded on the basis of merit.

If you require any further information please contact the Graduate School Office e: maps.pgr.admissions@leeds.ac.uk