INTERNATIONAL YEAR OF CHEMISTRY Remediation of indoor air pollution

1. INTERNATIONAL YEAR OF CHEMISTRYRemediation of indoor air pollution ISAAC W MWANGI

2. Background • Chemistry is a big part of modern mans everyday life. You find chemistry in daily life: food, air, soap, your emotions and literally every object you can see or touch. • In our abode, chemistry is the building block of construction. It’s used in every component of all infra structures. Chemistry helps save energy and creates environments that are healthy, safe and comfortable. •  One is justified to say that chemistry is the key to everything we use on earth and we can therefore lead a better life with chemistry. • THE CHEMIST, A PROFESSIONAL PARTNER IN ALL ACTIVITIES, not reward nor regarded.

3. Pollution • It is expected to be refreshing to be in the house after a tiring day, leaving behind the noise, air and light pollution of the traffic hoping to come and relax. •   But that pollution rest in wait indoors to welcome the occupant. • Indoor air quality (IAQ) needs attention because of the effects it has on human health. • There are several pollutants that compromise the quality of comfort we expect in our homes.

4. Pollutants and causes • They are:- • Organic chemicals around the house, such as floor cleaners, paints, disinfectants, detergent and polish. • Gases from cooking and combustion. • Furniture materials like plywood, particle boards and insulating foam and laminate- contain compounds like formaldehyde, toluene and acetone. • Humidity in the house encourages the growth of fungi, moss and bacteria, which release spores into the air. • Indoor flowers that release pollen and volatiles • Waste from persons and pets living in the house and even emitted tobacco smoke and exhaled human breath • Gases like nitric oxides (NO and NO2), sulphur dioxide (SO2). and ammonia (NH3) and volatile organic compounds (VOCs)

5. Pollutants and causes

6. Pollutants and causes

7. Problem These can deny the resident comfort and cause serious health problem like drowsiness, headache, sore throat, mental fatigue and can cause asthma, skin rashes, irritate the eyes and lead to allergies Solution A chemist should use the knowledge acquired to make a tangible difference to society by picking scientific problems that are challenging such as indoor pollution. Traditional methods Increasing the air exchange and using air purifiers. These methods have the following disadvantages. This might transport more pollutants from outdoor environment (Jones 1999).This creates another problem Jones, A. P. (1999). Atmos. Environ. 33: 4535-4564.

8. Objectives • The idea is to compare reactions taking place in natural systems and consider their applicability to solve existing problems of indoor air pollutants as it relates to human exposure. This should be a medium and long-term solution. • An example is that researchers have found that when pollution by ozone passes over a forest, a significant fraction of it disappears. This is because it reacts with VOCs from the trees (Kurpius 2003) • Establish a similar reaction in the house • However introduction of gases in the house might complicate the situation. • Kurpius, M. R., Goldstein, A. H. (2003). " Geophys." Res. Lett. 30: 1371.

9. Specific objectives • Taking the forests case where ozone is stripped off oxygen by the volatile organics should be proposed and be realised by use of heterogeneous photocatalytic oxidation (PCO) (Fujishima 1972) • Use of TiO2 photocatalytic oxidation should be the solution • TiO2 has a limitation- can only be activated by UV light (Kuo 2007). • It has to be modified like carbon-doped TiO2 with a cut-off wavelength of 535 nm (band gap of 2.32eV) that corresponds to bluish green light (Blöß 2007). • TiO2 promotes ambient temperature oxidation of the major indoor air pollutants and no other chemical additives are required. • Fujishima, A., Honda, K. (1972). Nature 238: 37-38. • Kuo, C. S., Tseng, Y.H., Huang, C. (2007). " Carbon-containing nano-titania prepared by chemical vapor deposition and its visible-light-responsive photocatalytic activity." J. Mol. Catal. A-Chem. 270: 93-100. • Blöß, S. P., Elfenthal, L. (2007). Doped titanium dioxide as a photocatalyst for UV and Visible Light. In: , Environment and Construction Materials TDP. Proceedings International RILEM Symposium on Photocatalysis. Florence, Italy

10. Justification • TiO2 is the best photocatalyst because of its excellent properties like safety, low price, stability, and high photocatalytic efficiency (Obee 1995). • TiO2 products are used in domestic paint products • They are mechanically stable support material to anchor chelating agents. • Obee, T. N., Brown, R.T.: (1995). "TiO2 photocatalysis for indoor air applications: effects of humidity and trace contaminant levels on the oxidation rates of formaldehyde, toluene,and 1, 3-butadiene." Environ. Sci. Technol. 29: 1223-1231.

11. The chemistry of heterogeneous photocatalytic oxidation reaction • Electron plus hole generation • TiO2 + hʋ e- + h+ • Formation of electron and hole pairs • Adsorption of the reactants onto the photocatalyst Free radicals • TiO2 + H2O TiO2_H2O • TiO2 + O2 TiO2_O2 • TiO2 + NO TiO2_NO • Recombination of the generated electron and hole pairs: • e- + h+ Heat

12. The remediation mechanism organic species of the form - RH Since the surplus of oxygen is maintained through photo catalysis, the reaction is allowed to continue, multiple hydroxylated products will be formed in the case of aromatics and complete oxidation to C02 occurs eventually (Matthews 1992). This bring the idea of application remediation of on indoor air quality by use of photocatalytic technology. Matthews, R. W. (1992). "Photocatalytic oxidation of organic contaminants in water: An aid to environmental preservation." Pure &App/. Chern.64(9): 1285-1290.

13. Methods • The carbon doped TiO2 can be deposited onto fibrous material, which then mounted on plaster boards and placed as ornamental wall hangings • Thin films of TiO2 be applied on the interior walls of a house • Ceramic tiles with TiO2 coated surface used for interior decoration • TiO2 coated paper could be used as wallpaper • All these remove various pollutants indoor ( Zehua et.al., 2008). • Efforts should be made not to compromise on the beauty of the house. Zehua, L. An,Y., and Ranran, M. (2008) Removal of indoor pollutants by nano TiO2/β- cyclodextrin coated paper under UV irradiation Laboratory of Pulp and PaperLaboratory Tianjin University of Science & Technology

14. The schematic diagram of the photocatalytic oxidation set-up

15. Schematic diagram of TiO2 onto the glass fibres gypsum plasterboard paper The board is ready to be placed on the wall as an ornament without compromising the beauty of the house (Puddu 2010) Chemists making homes healthier keeping them pollution-free

16. Degradation of food stains Applications: • Living rooms, kitchens, bathrooms and basements

17. Pictorial representation of heterogeneous photocatalytic oxidation (Puddu 2010) Puddu, V., Choi,H., Dionysiou,D.D., Puma,G L. (2010). " TiO2 photocatalyst for indoor air remediation: Influence of crystallinity, crystal phase, and UV radiation intensity on trichloroethylene degradation " Applied Catalysis B: Environmental94: 211-218.

18. How does it work? The chemist says, turn the Lights On and see a Miracle! When exposed to light, the titanium oxide shows its true strength:By destroying odours, pollutants and even tiny spores. Due to this photo-catalyticreaction, germs and dust cannot adhere to walls or ceilings, they are broken down and cleaned. A silent-acting permanent process without any side effects. Increasing the intensity of light (artificial light or daylight) will boost this self-cleaning process, eliminating even heavy contamination.

19. ACKNOWLEDGEMENTS • I wish to thank ANENMS (ANALYTICAL-ENVIRONMENTAL & MATERIAL SCIENCE RESEARCH GROUP) Research group for support • THANK YOU ALL FOR LISTENING 19