Fijs van Leeuwen (promotion date: 31 March 2005)

Selective extraction of naturally occurring radioactive Ra²⁺ from aqueous waste streams.

Extraction based on Thiacalix[4]arene and iso-guanosine

Promotion date: 31 March 2005

What was your thesis about?

Radioactive material does not only occur in the waste of nuclear plants, but one of the main sources actually is the environment we live in. One example is the naturally occurring radioactive element uranium and its decay products. For example, when drilling for oil saline well water, holding decay products of uranium e.g. radium, is pumped to the surface together with the crude oil, releasing these elements in to the environment. At the time the project was initiated, there seemed to be an industrial necessity to get the radium out of these produced waters, which led to the sponsoring of this project by the oil and gas (and pigment) industry. Consequently, we set out to develop molecules that could selectively remove radium ions from all the non-radioactive substances in wastewaters.

So this leaves you with a waste product to get rid of?

Polluted water of e.g. the oil and gas industry is produced in huge quantities, making proper disposal very difficult. If we were able to concentrate the radium ions it would leave us with only a small volume of radioactive material, which can be properly disposed of at the Dutch depot for radioactive waste (COVRA).

Is there a measurable increase of radio activity in the oceans?

No, not really, it diffuses quite quickly.

So why bother when there is no measurable increase or threat?

Legally, it is not allowed to release water streams with changed chemical matrix into the environment. Furthermore, radium ions can also be found as pollutant e.g. drinking water, were does pose an actual health threat. This makes the development of know-how on its selective removal very appealing for the (future) implementation in the purification of drinking water.

What was your main result?

We were able to surpass the objectives of the project, which was to selectively isolate one-part-per-million radium from a suspension comprised of numerous other elements. We even succeeded in isolating one-part-per-hundred-million! Besides, we only needed a surprisingly small quantity of radium complexating agent, owing to the fact that we developed highly selective agents.

How is this connected to nanotechnology?

The fact that the research performed was at the molecular level. This means that we actually build compounds and performed chemical recognition with them at a nano/angstrom levels.

Is your method going to be deployed?

We have worked as realistically as possible, even using real produced water from oil/gas rigs. However, the research performed remains to be of a fundamental nature. There is still a substantial amount of research to be done on the engineering front before it can be implemented as e.g. ‘radium kit’. It is thinkable that due to the development costs our method will never be used in the oil industry, yet it may be useful in purifying drinking water. In countries such as the US where a large supply of the drinking water comes from well water, radium posses a significant health problem.

What did you like best about your research?

The fact that I was working at a practical problem, or at least, had the illusion.

Did you have moments of frustration?

Of course I had, like everybody doing scientific research. Being completely in the dark in the beginning was difficult, but as soon as I found my way it all when a lot better.

For the summary of the thesis, click here.