News Water quality


Shells to clean wastewater


Anthony King


useful as photocatalysts to break down difficult to treat chemicals


Scientists have converted waste mussel shells from the food industry into a mineral found in bones and teeth that may also prove valuable for cleaning wastewater. In the presence of UV radiation, the researchers found hydroxyapatite (HAP) generated chemical radicals that degraded methylene blue, similar to compounds found in textile wastewater, in both oxygen poor and rich conditions. Usually, semiconductors such as titanium catalyst (TiO2


) are


in the final stage of a wastewater treatment plant. However, titanium is expensive and there is limited availability. ‘We found that HAP is pretty good as a photocatalyst, though not as good as titanium dioxide. But it comes from waste and we think there is also an advantage in that it comes from atoms that are not limited in the world – calcium and phosphate,’ lead scientist Darrell Patterson at the University of Bath, UK, explains. The HAP used was generated by crushing and then heating mussel shells to 800°C to convert the calcium carbonate (CaCO3


) in shells to lime (CaO); Theoretical chemistry Nobel-prizewinning research Maria Burke


The 2013 Nobel prize for chemistry has gone to three theoretical chemists: Martin Karplus (University of Strasbourg and Harvard University), Michael Levitt (Stanford University School of Medicine) and Arieh Warshel (University of Southern California, Los Angeles). They laid the foundations for modern chemists to simulate complex chemical reactions on a computer, work that has allowed for much deeper understanding of how chemical processes happen, and led to design of better catalysts, drugs and solar cells. The three theoreticians laid the groundwork for linking classic experimental science with theoretical science through computer models to simulate how chemicals interact with each other. Classical Newtonian mechanics is good at modelling really large molecules but offers no way to simulate chemical reactions. Quantum physics can simulate reactions but requires enormous computing power even for small molecules. Based on work started in the 1970s, the


three found a way to combine both classical and quantum physics into a ground-breaking technique called QM/MM. From simulating the spectrum of organic molecules such as diphenylhexatriene,


6 Chemistry&Industry • November 2013


the researchers extended the QM/MM approach to larger molecular systems and demonstrated its ability to model the folding of a simple protein – bovine pancreatic trypsin inhibitor – and the formation of a carbonium ion in the active site of the enzyme lysozyme. This is important recognition for a major advance in theoretical chemistry, says Martyn Poliakoff, vice-president of the Royal Society. ‘Their novel approach combined both classical and quantum physics and now enables us to understand how very large molecules react. This prize highlights the increasing role that theoretical and computational chemistry are playing in this area of science.’ Richard Henderson is a former director of the


MRC Laboratory of Molecular Biology (LMB) in Cambridge, UK, where a key part of the prize- winning research was undertaken in the 1970s by Levitt and Warshel. ‘Their early work on energy minimisation and its evolution into molecular dynamics has developed into a worldwide industry. It has permeated into all aspects of structural biology, from protein folding to drug design, to supramolecular interactions. Hopefully, it will soon be possible to compute the structure of almost everything, even if not with perfect accuracy.’


Meanwhile, the 2013 Nobel prize in physiology


or medicine was awarded to James E. Rothman (Yale University), Randy W. Schekman (the University of California at Berkeley) and Thomas C. Südhof (Stanford University) for their research on how materials such as hormones, enzymes and chemical signals, are transported in and out of cells at the right time and to the right place. Rothman identified the protein mechanisms


that allow small packages in cells called vesicles to connect with their destinations, while Schekman pinpointed the necessary genes for vesicles to move from one place to another, and Südhof revealed how signals instruct vesicles to release their cargo with precision. ‘The simplicity and elegance of their findings


provided an explanation of how a few molecules can provide a “postcode” for vesicle delivery,’ says Mike Cousin of Edinburgh University, UK. This basic biological finding has underpinned studies of how cells communicate within and between themselves, he adds. It has recently become clear that dysfunction


of vesicle trafficking events triggers a number of neurodevelopmental and neurodegenerative diseases, such as autism, schizophrenia and Alzheimer’s disease.


water and phosphate were then added, under controlled conditions with no oxygen, to generate HAP after a few hours. ‘I believe will be easily scalable,’ says Patterson. The next step is to scale up to see if the costs and benefits balance out and to see how effective it is against recalcitrant wastewater contaminants. ‘Our priority chemicals are


endocrine disrupting compounds, so things like hormones, some pesticides and pharmaceuticals, which are hard to break down conventionally in wastewater treatment plants, but can be broken down by technologies like photocatalysts,’ he says. The HAP –


produced in a collaboration between Bath and the University of Auckland in New Zealand – was comparable to commercial HAP. Around 39% of the methylene blue was degraded after 6 hours under oxygen limited conditions; under oxygen rich conditions, degradation during the initial 6 hours was around 54%, increasing to 62% after 24 hours. However, Darren Sun at


energy intensive process,’ he says.


Nanjang Technological University in Singapore, questions whether the process will be cost-effective. ‘To convert [calcium carbonate] together with organic materials to [lime] and release CO2


is also an


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