A Combined Computational and Benchtop Chemistry Approach to a Model of the Formation, Growth and Precipitation of Hydroxyaluminosilicates.

The form of dissolved silicon which is found in natural waters such as lakes, rivers and the sea is called silicic acid. A molecule of silicic acid is composed of an atom of silicon surrounded by 4 hydroxyl (OH) groups in a tetrahedral arrangement. This molecule can almost be described as chemically inert as it has no known organic chemistry and almost no known inorganic chemistry. The latter is the subject of this proposal as we have identified the unique inorganic chemistry of silicic acid with aluminium in forming what we have called hydroxyaluminosilicates (HAS). We have been able to identify how the neutral silicic acid molecule reacts with a 'surface' composed of aluminium hydroxide to form two discrete HAS which we have called HAS'A' and HAS'B'. We have been able to confirm the structures of these solid phases and assign quantitative data to their composition and solubiblity. We have shown how they may also incorporate both fluoride and phosphate in their structures. All of our achievements in this field have now resulted in this chemistry being included in authoratative text books on inorganic chemistry. However, there is a great deal still to learn about HAS and in particular how their rate of formation will have profound influences upon their chemical and biological roles in specific environments. We have identified HAS as critical secondary minerals in the biogeochemical cycles of both aluminium and silicon. Thus we know that this chemistry plays an important role in the biological availability of silicon, for example, for biosilicification (organisms which build silica frameworks for structural roles) and aluminium, it keeps aluminium out of biota. The latter role of silicic acid as the natural antagonist to the potential toxicity of aluminium has been widely demonstrated by ourselves and, following us, many other groups and is probably the major role of silicon in living organisms. Thus gaining as much understanding as is possible about the formation of HAS will not only enable some new and exciting inorganic chemistry it will also inform us as to the role this chemistry plays and has played in biochemical evolution. In particular, in this project we wish to build a computational model of the kinetics of HAS formation as such a model should be invaluable to any application where it is important to be abe to predict the biological availability of aluminium. We will use state-of-the-art benchtop chemistry including particle-sizing and mass spectrometry to establish new and innovative data concerning how HAS form, aggregate and eventually precipitate as kinetcially inert secondary mineral-like solid phases. These data will be used in our new kinetic model of HAS formation to produce an effective and predictive computational model which will be readily accessible by many different interested parties including applications in fundamental chemistry but also in applied chemistry and in toxicology.

It is never easy to predict who might benefit from fundamental research. It is often someone on the 'outside' who is able to see an application which may never have been clear to those developing the ideas. However, we now live in what I call The Aluminium Age and the consequence of this is that we are already using aluminium in myriad applications and we are actively developing new uses of this exceptionally versatile metal. To this end there could be a diverse set of end-users of the science we will generate in the described research. Beneficiaries within the private sector could include those developing technology relating to pollution monitoring and control; those using aluminium in water treatment; any industry which uses aluminium in processing including the food industry and the pharmaceutical industry. Since aluminium is a known ecotoxicant it is clear that anything which helps in understanding, and indeed predicting, its biological availability will be of great interest to policy makers for example, those charged with protecting the quality of surface waters; those whose role it is to guarantee the safety of foods and similarly the safety of pharmaceuticals, nutriceuticals, cosmetics, etc. It is less clear how our research might impact directly upon the public sector or the public at large. Clearly a successful model such as we will produce herein could be taken and used in other applications involving time as a critical factor and as such the model may find a number of roles related to this including as an educational tool both within and outside of the formal educational system.The question of how our research will benefit the various end-users is in many ways simpler to forecast. Even when limitting such to the subject of aluminium it is clear that the current use of aluminium in modern living is on an upward trend, reflecting the amazing versatility of this metal, and so we need to be absolutely confident that we understand the biological availability of this metal so that it can be used effectively and safely in its myriad current and future applications. The continued safe and effective use of aluminium in everyday life has enormous financial implications, imagine the opposite, of suddenly finding out that aluminium was not safe to use and thereafter having to find replacements for its diverse sets of applications. Stock markets would falter if not crash at such a situation! This understanding which the UK and our group specifically leads internationally is also something which could be exported. The knowledge economy is one of the most significant contributors to GDP for developed economies and the possibility of exporting the UK lead on the understanding of the biological availability of aluminium must be something to be considered.The named PDRA on this project is a computational scientist of great flare and ingenuity and will additionally benefit enormously from participating in a project which could extend to such a diverse set of end-users and beneficiaries. While we have tried to identify those who might immediately benefit from our research it should be clear to all that if aluminium exposure contributes towards chronic human diseases then we will all benefit from the knowledge and tools required to continue to use it both effectively but importantly safely.