Tuesday, 29 December 2009
Tuesday, 22 December 2009
Cellulosic fibres exhibit a number of properties which fulfill the requirements of papermaking. These properties are: High tensile strength, suppleness (flexibility), resistance to plastic deformation, water insoluble, hydrophilic, have a wide range of dimensions, inherent bonding ability, ability to absorb modifying additives, chemically stable and relatively colourless.
Deinking chemicals are used for the removal of ink when recycling paper.
The deinking chemical agents are based on formulations of:
- Sodium hydroxide
- Sodium hydrosulfite
- Hydrogen peroxide
- Chelating agents
I use 1 litre of each and add them to the deinking cell in a specific order.
Deinking process can be broken down into several simple stages.
Recycled waste paper ----> screening and cleaning ----> wash deinking or flotation----> deinking post-flotation and dewatering.------> deinked pulp
Recycling technologies have been improved in recent years by advances in pulping, flotation deinking and cleaning/screening, resulting in the quality of paper made from secondary fibres approaching that of virgin paper. The process is a lot more eco-friendly than the virgin-papermaking process, using less energy and natural resources, produce less solid waste and fewer atmospheric emissions, and helps to preserve natural resources and landfill space.
However there are alternative ways of deinking paper which involves replacing harsh chemicals with enzymes. This is what I research.
Enzyme action is affected by the paper constituents in the de-inking condition. The chemically pulped fibres are more susceptible than mechanically pulped fibres. This is important because mechanical fibres have a lot of lignin left and hence they're much more resistant to the cellulases. Therefore, this technology works best in mills that are recycling stock paper such as office waste which is very high in chemical pulp content.
Office waste paper, unfortunately, is also high in laser and toner content, thus it has a very low value because you can't mix it with anything, and the technology for taking the toner particles out is not very good at the moment.Enzyme deinking is complemented by maceration, because the major role of cellulase is to release the toner particles from the surface of the fibre. One depends upon the mechanical action in the pulping process to release the toner particles, and physical separation remove the toner particles by flotation.
During the past twenty years the attempt to replacing chemicals with enzymes in deinking recycled paper including cellulase, xylanase, laccase and lipase, has been pursued. Cellulases and hemicellulases have been demonstrated to dislodge inks by peeling off fibres or fines on paper surfaces. Lipases have shown some direct action on ink particles either degrading oil carriers or breaking down pigments. Lignin-degrading enzymes, such as laccase, also hold some potential for deinking, as they may selectively remove surface lignin, and hence, facilitate ink removal. Cellulolytic enzymes have shown the most promising results for deinking of mixed office paper waste. I suppose this is to be expected since paper is actually cellulose. Oddly I personally am finding that amylase is the most effective at deinking. What is frustrating though is that after the end of my experiments/deinking sessions I am finding that there is so little enzyme activity left making it difficult to assay. Isn’t that typical of science?
Enzymatic versus chemical deinking has been widely examined for MOW (mixed office waste) and photocopy prints. This being the most difficult paper to deink. The use of enzymes could be an attractive alternative to chemicals in deinking. The application of enzymes in deinking has been studied on laboratory and pilot plant scale. This work has resulted in numerous patents. However, so far enzymatic deinking is rarely applied in commercial use although some promising applications include recycling. The enzymatic treatment is a competitive alternative for MOW and photocopy paper deinking. However, the process requires the selection of an adequate enzymatic preparation for each paper grade. It is less costly than chemical deinking, and it is more efficient.
These 2 methods of deinking are constantly being compared and work with enzymes will continue due the benefits gained by using them. I will leave actually paper making to the experts though I have done and enjoyed that activity.
Saturday, 12 December 2009
Sunday, 6 December 2009
I’m guessing that not many people in the blogosphere will know much about the art and science of papermaking so here is a quick guide. Just what exactly is paper? I will tell it from the point of view of a chemist ;D
It is composed of carbon, hydrogen and oxygen which of course means it is a carbohydrate. This is in the form of cellulose which itself is a long chain linear polymer of β-(1 4)-D-glucopyranose units in 4C1 conformation (i.e.glucose molecules)
Cellulose is found in plants as microfibrils, and is mostly prepared from wood pulp.
It is also produced in a highly hydrated form by some bacteria (for example, Acetobacter xylinum). So as you can now imagine, the chemistry, physics and process of papermaking is quite complex and very interesting I assure you.
Paper is such an important piece of our lives, but what do we really know about it? Papermaking began in China back in 200 BC. Chinese papermakers used old chopped-up fishing nets, tree bark, and scraps of linen and hemp to make the world's very first paper. Chinese papermaking spread slowly but steadily all over the world, from Asia into Africa and Europe. Soon just about everyone knew how to make paper. Still, there wasn't a lot of paper around, since making it gobbled up a lot of paper-making material. Early paper was made of rags, and rags were hard to come by. Ironically, when the disease called the Plague or Black Death killed millions of people in Europe, tons of clothing and rags became available - at just about the time the printing press was invented. Suddenly, more books were printed, people became better educated, and these better-educated people scratched their heads, trying to figure out a substance that might provide even more paper-making material.
We still make paper using that same basic formula. We just vary the kinds of wood fiber and energy, and the techniques of bringing it all together, to get just the kinds of paper we want. There are certainly many types of paper - newspapers, school books and writing stationery; envelopes, boxes, packing and wrapping paper; paper toweling, tissue, and personal hygiene products. Not a day goes by that we don't use paper in dozens of ways. But papermaking today, creating all the kinds of paper we use in such huge quantities, is a science as well as an art. Engineers and technicians speed things up, using computers to help guide factory machines that can produce huge rolls of paper at more than 45 miles an hour. (Thanks to TAPPI). Here is a photo of our dept pre 2004 before we merged with our textile friends.
And here is a photo which graced the entrance to our building. Sadly it was taken down and I miss it :( I hope to see it pop up again somewhere. Hopefully in one of our museums. I shall keep looking............Do you think we will need as much paper in the future as we become increasingly dependent on modern technology? Hopefully people will still treasure books as they read from their kindles. Of course we will always need tissue paper. A post in the near future will be about the biology and chemistry of paper recycling which is what I do.
Friday, 27 November 2009
Why do I want to talk about trans fats? Recently I caught a repeat on our new digital tv screens of a program hosted by Top Gear’s Richard Hammond. He wondered wether we should be worried about trans fats and at one point went into a sewer (in protective clothing) and the stench was apparently MUCH worse than he was expecting. We were shown huge pile of fat from fast food outlets and restaurants which had taken up residence down there. Not what I expected, they looked like giant piles of ash! The outcome of this show (yes they had a chat to a professor of nutrition), was that if we are eating 2 or 3 takeaways a week then we are putting our health at serious risk. This was in 2006 and I think people maybe in need of a reminder of exactly what trans fats are and which foods contain them and so to avoid. Hence this post.
Everyone has heard of them and knows that they are very bad for us, but what exactly are they? Any organic chemist or good food nutritionist ought to be able to tell you. So here is a quick chemistry lesson.
At room temperature, oils are liquids and fats are solids. The reason has to do with their chemical structure. The main backbone of all fats is a long chain of carbon atoms. In nature, fats contain some double bonds, these are what are known as unsaturated fats.
It is at these double bonds that addition of hydrogen takes place.The double bonds are broken during such reactions and the end product consists of a new single bond. This is now a saturated molecule/fat. There are 2 ways in which these new hydrogen atoms can add to the molecule which means there are 2 types of resulting
fats. Look at the carbons marked with a red asterisk. Both hydrogen atoms are bonded on the same side of the carbon atoms. This is known as a ‘Cis’ fat. This occurs in most cases and causes the chain to be bendy. Cis fats occur naturally. However during the manufacturing process, bombarding the chains with hydrogen results in the 2 new hydrogen atoms being attached on opposite sides, i..e a trans fat.
This gives a more solid structure. As a result trans fats are found in large amounts in dairy products and meats. Health implications of trans fats are cancer, diabetes, heart attacks, strokes, reduced sex drive and just generally not feeling great.
Its best to eat a sensible diet making sure it contains enough fruit and vegetables and using vegetable oils rather than solid butter. Be sure to ask your local chip shop etc if they use hydrogenated oils. Lets hope they say no and they are telling the truth.
Saturday, 21 November 2009
The UK city of Manchester and its university are the proud hosts of Jodrell Bank which itself is of course most well known for the Lovell Telescope.
This blog is quite 'spacey' thus far isn't it? Thats okay, its a beautiful and currently topical subject. I shall endeavour soon to diversify, maybe with some chemistry ;)
Here is a link to a 4 part guide which tells you everything you could want to know about the LHC which was restarted last night. Particle Physicists are hoping to find out more about the nature of the universe and it would be very exciting if they find the much sought after Higgs-Boson (aka 'God') particle.
Good luck to them, many of us are following whats going on especially via the wonderful 21st century medium known as Twitter
After a 14 month hiatus, the LHC restarted yesterday
Wednesday, 18 November 2009
Everything you need to know about this festival you can find on their website. It also comprises of a blog which is regularly updated.
There were very many events taking place over Greater Manchester, quite alot at MOSI (Museum of Science and Industry) where I spent most of my time and also where I had my training. This the third year of the festival but the first one for me so I was very excited.I got to meet and work with lots of lovely people. The kids were alot of fun and this was good experience for me working with them. I learned new things eg DNA modelling with wire and coloured beads. I got to see things many great things too. For example a replica of the Mars Rover, which was very impressive. Also 'Baby' which was the first ever computer to be constructed and it was built here in Manchester. As a special treat for kids, in the special exhibitions hall was a CBBC interactive booth. This was ran by a lovely guy called Isaac who's come all the way from London for this. When I was not wearing my purple STEM Ambassador T-shirt I was a CBBC volunteer so it was a full and busy week for me. Alas we weren't allowed to keep our white t-shirts:( My first day at the festival, was spent at The Manchester Mueseum which is part of Manchester University. Here I watched and helped the kids with the Darwin Tree of Life. Before their arrival, it was a case of securing wallpaper to the floor with duct tape and stenciling the title in the middle of it. The idea is that the kids look around the museum and decide upon which animal they see which they would like to draw. Then they come to us and get to draw it on the Tree of Life. They then have to draw a line connecting it to another creature which has similar features. Great fun. Photographic evidence of this and me doing my CBBC stint can be seen on my other blog. I may get around to shift them over here http://sarahstracks.blogspot.com/The next day was an entire CBBC day for me. Plenty to entertain the kids. There was a mobile treasure hunt, all texts free of course. This took the kids around the museum so they get chance to see everything, only 4 clues and should take 30 mins max. Then they come back and whisper to us hopefully the correct answer. They recieve a very colourful swish certificate and a multilingual pencil as well as getting to watch a 60 second animation. They can then do the Bamzooki workshop if they want but the text hunt isn't compulsory. Apparently Bamzooki is a kiddies CBBC show which I'd never heard of, haven't been a kid for a loooooong time! Anyway the kids get to design and build their own robots and then fight each other Robot War style! All on computer and this was all set up and designed by resident computer genius, the lovely Bjorn whom I assume to be swedish. The kids could also invent something, draw their ideas and stick their drawings on the invention wall. Or they could make cardboard models of characters from CBBC shows. Again my ignorance of those was overwhelming. Or they could make a 'chatterbox'. Remember those? This one has scientific questions in it. This certainly kept the kids amused and they seemed to really get into it. They could wear labcoats if they desired as well as a silly 'thinking cap'. I must say I found my CBBC time to be a very rewarding blast. I enjoyed it immensely. Whilst occupying the kids the adults could look around at the other stalls which were there. All scientific of course. I was impressed that in the latter half of the week was a stand all the way from St Andrews University. The next day I was with STEM again. I spent the morning on the information desk and then had great fun in the afternoon doing DNA modelling with wire and coloured beads. I got to see a lecture by Prof Frank Close of Oxford. Basically he was just plugging his new book 'Antimatter'. I acted as Usher letting people in, got to see the lecture and then escort the prof out. I was supposed to take him to the info desk and book him a taxi but as it wasn't raining he wanted to walk. The final weekend of the festival was significantly quieter but I think thats good, people get a better chance to look at everything, though that really hasn't been a problem all week. I did my STEM duty again on saturday spending some time on the information desk. I was told to go and see if anyone in the exhibition hall needed me. They didn't but this gave me a chance to look around properly. There was a spare desk where the DNA modelling had been so we did that again for a while as an extra. Then I did some paperwork (cutting out tickets). Not the most exciting day but I enjoyed it all the same. Sunday was the final day so I felt quite sad. I did my last CBBC stint in the morning until 1pm then donned my purple t-shirt for the final time. This consisted of ushering 2 lectures. The first involved a cab ride to Zion Art Centre in Hulme which I'd never been to before, its pretty cool. Large auditorium. Anyway a lecture called Horrible Science was given by Nick Arnold who is quite well know but not to me until now. He's written a series of books by that name and his lecture was full of silliness. Definitely for kids only followed by a book signing. Then we went to the university academic library John Rylands on Deansgate where there was an interesting lecture on the history of hypnosis. Yep he tried to hypnotise us in the end. No book signing this time, and that was it all over.........I'd certainly do this all again and would recommend it to anyone. As well as visiting such festivals of course. I think this will be my longest blog post ever ;D
I am now officially a STEM Ambassador for Manchester. This is a voluntary role of which I'm quite rightly proud. STEM stands for Science, Technology, Engineering and Mathematics. I will stay on the STEM database as long as I've participated in at least one 'event' every 12 months. That for me is the Manchester Science Festival though I will happily participate in any event which needs me in which I feel I can do and I have time for. This is a national programme and part of the British Science Association and obviously I represent Manchester as its where I live ;D. Our role is to promote and communicate the public understanding of science to non-scientists and to show children that it is is fun and exciting and not all boring equations etc. Hopefully it will encourage some to think about taking up a career in science in their future. I had a lovely tuesday mornings worth of training back in mid September which was great fun. We were taught and practised some science experiments which can easily be done at home with household objects. We would be performing these when out on the streets science busking! The festival itself ran from sat 24th Oct until Sun 1st Nov. On the run up to this though were plenty of events going on to promote the festival. A week before it started I enjoyed 2 science busking sessions in Stockport and Manchester Piccadilly train station respectively. All kids who walked by and stopped seemed to enjoy themselves, I had a blast although abit cold towards the end. In between these 2 days I spent a whole day as a volunteer with the schools programme. This took place in a nightclub and we had 4 schools, i.e. 200 kids! In the morning I ushered them into an auditorium to see a fun chemistry lecture given by Dr Steve Rossington of Salford University. Lots of blowing up of things! Then I ushered them out and steered them in the right direction. After a lovely and free lunch it was time for the experiments. They were on a rota system and I didn't get to see them all but did manage to walk around and talk to experts at the various exhibits. This is the first time I saw 'Baby'. Apparently it is nearly but not quite the original as most components have had to be replaced over the years. Still very impressive though, I'm happy to have seen it. The most fun thing I got involved with was CSI Manchester lol. Yep some brilliant young scientist had been murdered in his lab with his own retort stand and we had 4 suspects. I had a DNA sample taken so now I know how thats done. Of course it hasn't been tested/characterised! In the end the kids and adults all had a great day. It was nice to see smiling kids enjoying science xxx
..........2009 has been for Science. Well hasn't it? Lets see: 1) 40 years since man first set foot on the moon 2) International year of Astronomy 3) Charles Darwin's bicentennary (Happy birthday Charlie) 4) Discovery and naming of new chemical element #112, which is now officially called Copernicium. I'm sure there is something else? :/
Of course there was must excitement last year in Cern, Switzerland when they swtched on the Large Hadron Collider (LHC), in the hope of finding the Higgs-Boson or 'God' particle. This is of much excitement to physicists and in often true experimental style things didn't quite go to plan and the thing sprang a helium leak. So it will be swtched on again, this friday nov 20th. Of course they have already tried recently and a piece of bread from a baguette was apparently dropped into the machinery by a pigeon! I suspect this is not the exact story but do you think this project is jinxed perhaps? I look forward to it being switched on again and finding out what happens. Hopefully they will get lots of good data which they can use and will at least tell them something, good luck to them whatever happens. I can't wait for news of this.Here is a link to all you could want to know about the LHC
Hi Dear Reader,welcome to my first ever science blog. I really do hope you enjoy it. I shall keep it updated and active, lets see how it grows. First of all let me start by mentioning 2 of my online favourite chemistry projects, the now famous and award winning Periodic Table of Video's http://www.periodicvideos.com/# and also with musical accompaniment the ever lovely ChemToddler http://chem-toddler.com/ You can find the links to these 2 sites and much more of there on the left handside.You can also follow me on twitter @SarahScientist.
Any comments, suggestions, feedback etc are most welcome and I will be thrilled with sage advice/comments you wish to leave ;D.
Also of great importance to me is my other blog which follows my annual training for the BUPA Greater Manchester Run and raises funds for a charity which is close to my heart. The Rutger Hauer Starfish Foundation which supports and helps HIV+ pregnant women and children, initially in the Caribbean but now all over the world I think. That blog has the rather unimaginative title of 'Sarah in Training'
I'd better warn you that you'll hear alot about that come January!......
Take care xxx