Download Chemical waste

Chemical waste
ROBERT BROOK/SCIENCE PHOTO LIBRAR
Y
Where does it go?
In the school lab, the chemicals you deal with are easily
disposable but what about back in the technician’s store?
Chemical disposal
Pete Foulkes from ChemGo is one of the experts that
your school might phone. He explains that he is licensed
in the safe storage and transport of chemicals and often
goes into schools just to advise technicians on best
practice so that everything is as safe as can be.
The chemical store is where everything is kept,
portioned out for each class and taken back at the
end of the session. A safe store will have flammables
locked in a cupboard, far away from oxidisers and all the
Pete has also run training courses for firemen so that
corrosives will be stored together.
they know what to do if they are ever called to a chemical
As syllabuses change, chemicals that were once
spill, or an accident where chemicals are involved.
regularly used are not used at all, but technicians will
often save supplies in case they are needed once again. Pete says he is often called to schools when the science
department is moving as that’s often when people take
This means that over time shelves can get full and
eventually something has to be thrown away. When that stock and realise that they are still storing chemicals
they might not have used in years, or that are no longer
happens, the school will have to phone in an expert.
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JAMES KING-HOLMES/SCIENCE PHOTO LIBRARY
allowed to be used in schools.
Sometimes there are labels that are
no longer legible and Pete has to
work out what is inside the bottle.
Once Pete knows what he’s dealing
with, he contacts a transfer station
who agree to take and process the
chemicals. It’s Pete’s job to check
that the chemicals are what the
school says they are, and then to
transfer them safely to the transfer
station.
At the transfer station
At the transfer station, another
chemist will run tests to confirm that
Pete is delivering what is expected.
It’s very important that everyone’s
report of what chemicals are being
processed matches up and nothing
is sneaked in or missing. The tests
will range from simple pH tests to full
mass spectrometry analysis.
Once the chemicals are analysed, the different bottles
are tipped into separate containers: one for acids, one for
chlorinated solvents etc. It is then the transfer station’s
job to send the different containers of chemicals to be
disposed of. Where possible they send the chemicals
to be recycled but sometimes the chemicals have to be
dealt with in other ways, like burning.
A lot of what comes to the transfer station from schools
are acids and solvents and both can often be reused.
Acids contaminated with organic compounds can be
cleaned with steam and distilled. Acids with metal
contamination can be cleaned and reused using
dialysis through a semi-permeable membrane, leaving
contaminants behind. Sulfuric acid contaminated with
metals can also be concentrated and heated to give off
sulfur dioxide. This can be used to make more sulfuric
acid. Solvents can often be reclaimed using activated
carbon, which is a form of charcoal with a very high
surface area. Chlorinated solvents are tricky to recover
safely but can often be incinerated instead.
The transfer station doesn’t just deal with school
chemicals, but also old buckets of paint, out of date
cleaning products and even oily rags from garages.
The rags contain too much oil (over one per cent) to
be allowed into land fill. Instead the transfer station
squeezes out as much oil as possible, which can be
recycled, and then the oily rags are chopped up into
small pieces and sold to Germany where they are burnt
to provide heat and power.
The bottles that the chemicals came in are also recycled,
but that recycling is done in China. The Chinese take
the old bottles from the transfer station, as well as old
paint pots, and clean, grade and chip them. The chipped
plastic is then sold again and often used in this country
to make injection moulded plastics.
Plastic bottles and oily
rags can be recycled
So what happens to the chemicals in your school? Well
sometimes they can be recycled and sometimes they
need to be destroyed, but it’s always done as safely and
efficiently as possible.
Would you like to solve a chemical mystery?
Recently, students from a school in the midlands have
been analysing left over chemicals just like Pete from
ChemGo might.
Ironbridge Gorge Museum in Telford recently called in
chemists from Keele University to help them identify
samples in old bottles from their Victorian pharmacy.
Rather than just run the tests themselves, the Keele team
decided to enlist local school students to help out.
GCSE students from Sir Graham Balfour School,
Stafford, visited the museum and performed a variety
of experiments to try and identify the different potions.
Did you know?
Pete doesn’t just get called out to schools. He once spent several days crawling
around an airplane that had been taken to pieces; he was looking for mercury from a
broken thermometer.
Mercury can corrode through metal, including planes, so when a thermometer is
broken on a plane, it has to be taken apart and checked carefully before being allowed
to fly again. It was Pete’s job to climb around the aircraft with a mercury vapour sensor
and then suck up any escaped mercury. Once Pete had collected all the mercury, the
plane could then be checked for damage and put back together again.
If you break a mercury thermometer it’s unlikely you’ll do much damage but you
should avoid mercury contact with jewellery. Collect up the mercury mechanically (eg,
with a syringe). Mop up the remainder with a hot paste of 1:1 calcium oxide/sulfur
mixture in water.
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against reference samples, assuming that the earlier
identifications were correct.
PETER FOULKES
Peter Foulkes from ChemGo
unloads chemical waste at
the transfer station
Most of the samples turned out to be quite safe, despite
the labels on the bottles claiming to contain poisons
and disposal won’t be a problem. But Kathrine Haxton,
who ran the work at Keele, thinks it’s a shame that the
bottles in the museum will now be empty.
Following that, A-level students have then gone into
the chemistry department at Keele to run analytical
tests in the lab. The A-level students analysed samples
When asked what the weirdest sample the team found,
Haxton answered easily ‘rhubarb powder.’ Odd now,
but in Victorian times rhubarb powder was used an a
laxative and was so useful that it was more expensive,
by weight, than opium.
Laura Howes
Magnificent molecules
Phillip Broadwith, Chemistry World features editor, highlights one of his favourite molecules.
In this issue: nitric oxide
scrubbers in power plant exhausts
is to reduce these nitrogen oxides
(collectively known as NOx) back to
elemental nitrogen and oxygen.
several nearby cells all at once.
When tissues in the body become
inflamed for long periods of time,
the concentration of nitric oxide
within them increases. This can
NO as a molecular messenger
be used to diagnose disease. It is
The chemistry of nitric oxide inside
particularly useful for monitoring
humans and other mammals is
lung diseases like asthma,
perhaps the most interesting aspect
tuberculosis and even some forms
of this simple molecule’s behaviour.
of lung cancer. As NO can diffuse
NO is involved in controlling blood
through cell membranes easily
pressure – transmitting nerve
and is a gas, it gets breathed
signals and a variety of other
out. By tracking the nitric oxide
signalling processes. Its radical
concentration in patients’ breath,
single electron can also be used as
doctors can keep tabs on the
Nitric oxide is a colourless gas and
a weapon by the immune system
progress of the disease and the
has a single unpaired electron,
to kill invading bacteria. Its role
effectiveness of their treatments.
making it a free radical. On contact
in biology is so significant that
with oxygen it reacts to form brown
Monitoring by mobile
Science magazine proclaimed it
NO2. It coordinates strongly to
their ‘Molecule of the year’ in 1992.
An ideal way to carry out monitoring
transition metals – either using its
single radical electron to make ‘bent’ NO gas is produced within the body would be for each patient to have
a sensor that they could use every
nitrosyl complexes, or donating three by oxidising one of the nitrogen
day. That’s where the chemists are
atoms on the side chain of the
electrons to give ‘linear’ nitrosyls.
Although it has few direct uses itself, amino acid arginine with molecular coming into play. By developing new
kinds of sensors to detect NO, it may
oxygen. This is done by specialised
NO is produced industrially on a
soon be possible to have one built
tonne scale as an intermediate in the enzymes called nitric oxide
into your mobile phone. You can
Ostwald process for producing nitric synthases. When this happens in
the muscular walls of blood vessels, breathe into it and see an instant
acid from ammonia.
this stimulates them to relax so they indication of your health. At the same
Nitric oxide also contributes to
open up and reduce blood pressure. time, the data can be transmitted
air pollution, transforming into
over the mobile phone network to
When NO is produced in nerve
nitrous acid (HONO). Along with
update your doctor’s records.
cells it plays a special signalling
NO2, it is produced by burning
role. Because nitric oxide is a very
So, the baby of the nitrogen oxide
fossil fuels that contain nitrogen
small, uncharged and fat-soluble
family may not be as funny as its big
compounds. One of the main
brother N2O, but it certainly knows
functions of the catalytic convertors molecule, it can diffuse directly
how to get a message across.
in motor vehicles and the chemical across cell membranes and affect
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JOHN BAVOSI/SCIENCE PHOTO LIBRARY
Nitrogen forms many different
compounds with oxygen, which
have a bewildering array of
chemical properties and biological
action. The brown vapours of
nitrogen dioxide (NO2) are toxic;
whereas nitrous oxide, or N2O, is
used as an anaesthetic. N2O is also
known as ‘laughing gas’ because of
the tendency for people to giggle
uncontrollably after inhaling it. But
it is the simplest of the nitrogen
oxides - nitric oxide or NO - that I
am going to focus on here.
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