Mike Bullivant's diary about the challenge for the Rover programme, from the BBC/OU series Rough Science 4
Day One
Here we go again…. this time with a change to the team. Mikey Leahy’s place has been taken by Iain Stewart (an Earth Scientist) who, even within a few minutes of meeting him, I knew was going to fit in well. I arrived in LA from Perth (Western Australia) just under a week ago, and three days ago I had to pick the other four scientists and film crew up from Las Vegas where they’d flown to from Heathrow. We’ve all now spent a few days together, and it looks like it’s going to be a good team all-round.
Anyway, it’s the first day of filming, and there’s a lot to do. My challenge for programme one is to purify various samples of ‘impure’ water which Iain and Ellen are to collect from a variety of botanical and geological sources. Sounds easy enough, but where to start, given the limited resources I have at my disposal? I settle on charcoal (made from burning wood). In fact, I think NASA actually use charcoal filters to purify the air and water systems in their spacecraft. Charcoal is also used in domestic water filters. I suspect that ordinary charcoal will do, but there’s a chance I can make it an even more effective filter by ‘activating’ it – to do this I’ll need to blow air or ‘superheated’ steam through the hot charcoal, neither of which processes will be easy, or even possible, under Rough Science conditions.
My plan is to pack some two and a half centimetre diameter PVC tubing with plugs of charcoal and trickle the impure water samples (when I eventually get them) down the columns, under gravity. The charcoal is acting as more than just a physical filter to the impurities in the water. It’s an extremely porous material, containing, as it does, lots of tiny cavities, channels and pores. These all go to increase the material's surface area quite significantly. Incredibly, just one gramme of activated charcoal can have an internal surface area equivalent to five or six tennis courts. As the impure water works its way down the column, many of the impurities will bind weakly to the charcoal surfaces (a process called adsorption). The slower the trickle, the more efficient the purification process. The purified water should pass through unhindered, for collection at the bottom of the column.
Today’s goal will therefore be to make some charcoal.
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Content last updated: 18/07/2006
