Stink buster: The Zeolite quarry in Ngakuru, south of Rotorua.
The final Whanganui Science Forum of the year was held last week when Massey University professor Shane Telfer gave the Davis Lecture Theatre audience a story full of holes, as Frank Gibson reports.
The November Science Forum talk was about nothing — specifically it was about what you can do with the empty spaces within some materials.
A sponge has many interlinked spaces within it. Water soaks into the sponge because it is attracted into these spaces by electric forces between molecules and, having soaked up the liquid, the sponge can be taken somewhere else and wrung out, recovering the water.
That was the science required to understand the talk given by Professor Shane Telfer of Massey University.
So how do you get a job as a chemistry professor by wringing out sponges? It all depends upon what you soak up and how you wring it out.
We start with something simple. This is Zeolite, which is quarried in many places across the world, including the area south-west of Rotorua.
Straight out of the ground it costs about $100 per tonne. It is used in pet litter to absorb the smelly chemicals. On a larger scale, it is used to mop up chemical or oil spills and to absorbing composting odours. On a small scale, health shops sell it for about $25 for 100 grams (it is claimed to absorb body toxins), which is a mark-up of about 2500 per cent.
Professor Telfer's team, along with a number of other teams around the world, designs new materials similar in function to Zeolite but with very regular structures. The materials of the moment are Metal-Organic Frameworks (MOFs).
To the untrained eye, making MOFs looked like chemistry done with Lego on the kitchen table. Professor Telfer described mixing random chemicals and leaving them in the oven overnight to see what would happen. This was a smoke screen hiding details of the processes used to produce some of these potentially game-changing materials due to their lucrative commercial possibilities.
The world is addicted to petrochemical products. But it is not that simple. Between 10 and 15 per cent of energy produced in the world is absorbed into the petrochemical industry to produce the stuff we burn in our cars and aeroplanes. This energy is largely used to separate different molecules from the raw materials. Materials such as MOFs are being developed that can achieve the same effect without heat. These materials are filters engineered at the molecular level to have voids that only molecules of a specific size or shape can pass through. Reducing overall energy consumption by 10-15 per cent by changing the separation technology would have huge benefits both financially and ecologically.
Desalination of sea water uses a huge amount of energy, largely derived from fossil fuels. Apart from the energy used there is also evidence to suggest that the resulting increase in salinity of the sea around the countries has negative effects on sea life. A simple solution has been suggested.
During the cool hours of darkness, air is allowed to flow through a chamber that contains a type of MOF that grabs and holds water molecules. As the sun comes up, the chamber closes and the heat from the sun vaporises the water in the MOF. This is condensed and collected. The only energy input is solar.
A major contributor to climate change is carbon dioxide from fossil-fuelled power stations. Removing carbon dioxide from flue gases using MOF-based filters would have huge benefits. Storing the captured gas is another problem. Doing this underground in a medium of MOF would be much less prone to serious leakage.
Hydrogen-based fuel cells already exist. The main problem with vehicles based on this technology is the risk from having millions of vehicles each carrying a high-pressure tank of potentially explosive hydrogen. If a porous material can be developed that would hold significant amounts of hydrogen within its structure but in a manner allowing easy recovery, road transport could be revolutionised. Work continues.
To allow efficient transfer of nutrients, the effective area of the human gut is about half the size of a tennis court. This same principle affects the efficiency of storage batteries. The greater the effective surface area of battery electrodes, the greater the charge it stores. Battery weight is a major barrier to sustained electric-powered flight. Battery electrodes engineered at the molecular level are rapidly increasing the density of charge storage to the point that aircraft manufacturers are looking seriously at short-hop airliners (think Whanganui to Auckland) being electric powered within 10 years. On a world scale, the reduction in emissions would be huge.
It may have been missed by the audience but what I shall remember most about this talk was one superb example of how science really works.
Researchers in this field carry out complex calculations concerning interatomic forces and distances and use these to set up a computer simulation of what they expect a structure to be. The computer then produces a 3D model of the predicted structure.
Professor Telfer showed a slide of a computer-generated structure. He followed this with a slide showing a slice of a crystal of this new substance, and there we could see, on a scale of a few millionths of a millimetre, the same structure that the calculations predicted. The personal satisfaction for the scientists must have been amazing. It also shows the strength of the scientific method.
I met a friend in Pak 'n Save carpark not long before the talk. He was dubious about attending as he thought it sounded a bit nebulous. He missed something he could have really got his teeth into.
Next time you wring out the sponge in your bath, think about how great science can be born from simple ideas.
■ Frank Gibson is a semi-retired teacher of mathematics and physics who has lived in the Whanganui region since 1989.
Comment: There are food sources that have a stronger attraction for certain birds.