Oxidation of trace organic impurities in ultrapure water by UV and ozone

Abstract

In this dissertation, the chemical oxidation of trace organic impurities by the treatment of UV light alone, ozone alone, and the combination of UV light and ozone in ultrapure water is discussed. Eighteen model compounds are chosen as the representative organic contaminants. Significant synergistic removal effect by the oxidation of the combination of UV light and ozone has been observed on all model compounds except for trichloroethylene, benzoic acid, and methionine. The removal efficiency by the oxidation of the combined treatment is observed to be greater than that by the oxidation of UV light alone or ozone alone for all model organics. Based on the same injected amount of contaminants over a given period of time, it is shown that the amount of leftover material after one cycle in the loop in a run with ozone injection is lower than that in a run without ozone injection for most compounds. The photolytic ozonation improves the TOC removal efficiency not only on the UV unit, but also on the loop removal performance. The chemistry, advantages and disadvantages of all those three oxidative methods are discussed. The mechanisms of oxidative reaction for the UV/ozone interactions and of ion exchange in the deionized tank are proposed. The rate coefficient of each reaction for model compound is determined by fitting the model prediction to the experimental data. The metrology for modeling the whole ultrapure water system has been established. The mathematical derivations for that metrology are given. For the purpose of paving the road for the reuse of rinsing wastewater, three cases simulating TOC dynamic responses are discussed, and the chemistry between HCl and organics under the treatment of UV light alone is studied. The combined UV/ozone reaction has been proven to be a better way in removing organic contaminants in terms of particles population number density. The mathematical equation of particle size reduction with its breakage rate and fragmentation distribution function is proposed and validated with the experimental data. It is concluded that the surface erosion is the pathway of size reduction when organic particles are oxidized.