All Samples Comparable Degradation Testing

ReferencesTreatment of Methyl Orange by Photocatalysis Floating Bed by Enqiang Wang, Qiaoli Zheng, Shihong Xu & Dengxin LiPorous Titanium Dioxide Coatings Obtained by Anodic Oxidation for Photocatalytic Applications by Hernán Traid & María VeraEffect of metal-doping of TiO2 nanoparticles on their photocatalytic activities toward removal of organic dyes by M. KhairySynthesis of Silica Aerogel by Supercritical Drying Method by Tomasz Błaszczyński , Agnieszka Ślosarczyk & Maciej Morawski

Personal ExperienceThe placement for me has been invaluable and given me the opportunity to experience a working lab. I have taken part in projects and experiments containing complex chemistry and learned the practical things you cannot read in a text book about the workings of a research environment. I must thank Dr. Ian Mabbett, my Nuffield Project Mentor, Dr. Rachel Woods and Mr. Ashley Pursglove whose passion for their project was infectious. I could not help but be drawn into the excitement and enthusiasm that comes along with a project which has the potential to save many lives and be very successful. I am sure this project will succeed and am proud to be able to say I was a brief part of it. More than anything else though, it has re-affirmed my desire to follow this field as it has shown me the possibility to make a real difference and revolutionise a practise performed worldwide is available for those who are ready to work hard for it.

ResultsMy objective during testing was to gain results that showed the best type of TiO2 paste and which substrate produced the best samples. The graph below shows a directly comparable test as the conditions were constant for all of the samples I made. This is the major test I carried out during my project and it gives clear and incredibly useful results. The SSM with P25 has outperformed all of the other samples, next is also SSM with anatase, so I can say with certainty that the SSM is the best substrate to coat out of all the substrates used so far. Despite having the fastest initial rate, third is the FSSM with P25 which comes in before both GFM samples. The final 4 samples are the grout samples. This means I can suggest that, the best sample is the SSM then FSSM followed by GFM and finally the grout and overall, the SSM with P25 paste has ultimately performed the best.

FSSM Sintered GFM Sintered SSM Sintered

Testing and the Set UpThe substrate samples I made for testing were 80x80mm, the materials we used were either: glass fibre mesh (GFM), stainless steel mesh (SSM), an extremely fine stainless steel mesh (FSSM) or a ‘self-cleaning’ grout. Next I made the the TiO2 paste that is in the coating. The paste is made up from a mixture of water, polymer binder and TiO2 nanoparticle powder. The TiO2 nanoparticles are in the P25 form which is seen as the best photoactive blend between the rutile phase and anatase phase of TiO2. The paste must be viscous but also have flowable characteristics. I used a glass rod to coat the substrate with the paste using the draw down method. Next comes the sintering stage where you must place the sample in an oven or on a hotplate for an hour at 500oC, this is to remove any water or polymer binder from the coating to ensure full dispersion of the nanoparticles which maximises surface area. The substrate will be left with a thin TiO2 coating in the P25 form and is ready for testing.

To test the samples a shaker plate shook the dish to allow thorough mixing of the solution during the breaking down of the dye. UV lamps were used to provide photons to be absorbed by the sample. Distilled water was used for a zero value for absorbance from the UV/VIS spectrometer. 100ml of 10ppm indigo carmine dye was broken down in the test. An initial value was recorded before the sample and dye were placed under the lamps, this absorbance value was usually around 0.375 at 610nm wavelength. The test was run until the absorbance value at 610nm was zero or three concordant values were recorded in succession with an discrepancy of around 0.002 being allowed. Values for absorbance were recorded every minute for the first ten minutes then every two minutes from thereafter. The degradation showed a first order decay so this plan was suitable.

L: Samples I Made for Further Testing After My PlacementR: Polymer Binder Instantly Combusting Due to Heat at 750oC

Indigo Carmine Molecule

TiO2 Coatings for Degradation of Organics by Photocatalysis

by David Sharp

Photocatalysis Process Involving TiO2

Background ResearchTitanium dioxide (TiO2) nanoparticles can act as photo catalysts under certain conditions. They can be sintered at high temperatures onto a surface when heated in various ways including ovens, hot plate or near infrared (NIR) machines. If this surface is then irradiated with ultra-violet (UV) light it causes an electron from the valence metallic band to be excited into the conduction band. When this electron undergoes relaxation an electron (e-) and a hole (h+) pair are formed. If the pair survive recombination they will produce a highly reactive species and will cause further reactions. The h+ in the valence band will oxidise an anion to form a hydroxyl radical (.OH) whilst the e- can reduce surface absorbed oxygen molecules to yield superoxide radicals (O2

.-). These are an extremely reactive species. The hydroxyl radical is the main species that participates in my investigations by degrading dye that has contaminated water supplies. The dye we predominantly investigated was indigo carmine (C16H8N2Na2O8S2). This dye is used as a model dye and has other uses such as in jeans, milk and biscuits. However in high concentrations it is an irritant and can cause permanent injury to the cornea and conjunctiva.

During my Nuffield research placement I was part of an investigation into the treatment of water using photocatalysis after activating titanium dioxide nanoparticles under UV light. This involved investigating curing and deposition techniques of coatings with a view to integrating this concept into future factory builds and design.