Project No: 16307014

Title: Investigation of a new environmental catalyst for room temperature treatment of ammonia and hydrogen sulfide malodors in air

PI: Prof. Yeung, King Lun


Malodor is a particularly serious and difficult pollution problem in urban cities such as Hong Kong, where the large population and crowded space tend to aggravate the situation. Malodor can pose a serious threat to personal health and well-being. Prolonged exposure even at very low concentrations can cause olfactory dysfunction and psychological stress. Indeed, many psychosomatic symptoms such as insomnia, loss of appetite, allergy and even irrational behavior have been associated with malodor. In addition, it has an adverse impact on the commerce and value of the affected real estate. It projects an image of poor sanitation and an unhealthy environment. Malodor is a complex problem due to the large range of compounds involved, their low concentration and transient nature as well as an individual’s sensitivity to the different odorous compounds. Hydrogen sulfide (H2S) with its rotten smell, and the pungent ammonia (NH3) are the two leading causes of malodor complaints in cities. A new environmental catalyst for treatment of NH3 and H2S malodor in air was developed by a combinatorial method. The doped VOx/TiO2 catalyst is active for both selective oxidation of NH3 to N2 and partial oxidation of H2S to S6 at room temperature, while the best commercial and laboratory catalysts reported in the literature require at least 150°C. Furthermore, the catalyst does not produce secondary pollutants such as NOx and SOx. Most importantly, it tolerates high humidity (i.e., R.H. = 100 %) without a significant loss of activity (< 10 %) making it suitable for use in places where malodor is endemic such as water and waste treatment facilities, lavatories and sewer systems. The goal of the proposed project is to determine the nature of the active sites in the new environmental catalyst and reveal the reaction mechanisms and pathways in order to gain a deeper scientific understanding of the workings of the catalyst, and thus provide an engineering basis for further catalyst improvements in performance for treatment of H2S, NH3 and possibly other related malodorous compounds (i.e., reduced sulfide and nitrogeneous compounds) in ambient air.