UV ozonizing

The common oxidants are ozone, hydrogen peroxide, H2O, catalyzed usually with ferrous iron, Fe , and ia some cases chlorine dioxide and uv light. Advanced oxidation systems iaclude H2O2 + uv ozone + uv and H2O2, ozone, and uv. Depending on the appHcation, the oxidation can be complete to end products as in a contaminated groundwater or partial to degradable intermediate products as in a process wastewater. 

Ozone. Ozone generators are based on uv or silent discharge. Although uv ozone generators are marketed, they are not effective for treating... 

When the films were treated in either an oxygen plasma environment or under UV/ozone irradiation, the rates of oxidation were faster for the plasma process. Irradiation of chitosan solution showed that UV/ozone induces depolymerization. In both plasma and UV/ozone reactions, the main active component for surface modification was UV irradiation at a wavelength below 360 nm [231]. 

A (100) oriented p-silicon wafer (Wacker Chemitronic) was cut into 5x5 mm pieces. These were cleaned in a UV/ozone dry stripper (Samco) for 15 min followed by a two minute rinse in doubly deionized water. The samples were dried in clean air for several minutes. A 10 pi amount of TEOS (purchased by Aldrich, electronic grade, as received) was dropped onto the dried surfaces. The film was allowed to dry in ambient air for 10 minutes and then immediately transferred into the vaccum-chamber of the TOF-SIMS spectrometer. 

Kearney, P.C., J.M. Ruth, Q. Zeng, and P. Mazzocchi. 1985. UV-ozonation of paraquat. Jour. Agric. Food Chem. 33 953-957. 

Note that a native oxide film also forms under dry conditions in ambient air the oxidation rate of this process can be enhanced by ultraviolet (UV)-ozone photooxidation (Tal, Vil]. Oxide-covered Si surfaces exhibit low contact angles. Only if the oxide surface is contaminated, for example by a monolayer of absorbed hydrocarbons, may larger contact angles be observed. 

EVAs are naturally resistant to light, UV, ozone and weathering and, even more, they can be protected by addition of specific anti-UV and other protective agents. Under identical... 

Recently, Genzer and coworkers [85] presented an interesting new approach for the preparation of stable silane-based SAM systems. As a substrate, cross-linked polydimethylsiloxane (PDMS) was oxidized by UV/ozone treatment to yield a thin sihcon dioxide surface. The surface was then treated with fluorinated alkyltrichlo-rosilanes from the gas phase while being mechanically stretched by a certain length Ax. After modification, the elastomer was allowed to relax resulting in a mecdianically assembled monolayer (MAM) at the surface (Fig. 9.8). 

Fig. 9.8 Schematic illustration of the preparation of mechanically assembled monolayers (MAMs). (A) A cross-linked PDMS film is (B) mechanically stretched by Ax (C), oxidized by UV/ozone treatment to yield a thin Si02 sur-...

Dwell time, or the time the molecule was actually in the lamp unit, and concentration were two parameters that affected the rate of degradation. Mass spectra of the trimethylsilyl (TMS) derivatives of atrazine subjected to UV-ozonation revealed a number of dehalogenated, dealkylated s -triazines, paraquat yielded the 4-picolinic acid, and 2,4-D gave oxalic acid, glycolic acid and several four-carbon oxidation products. The economics of UV-ozonation as a pretreatment for land disposal compares favorably with incineration and other options open to the small pesticide user. 

Table I. Pesticides, Formulations and Concentrations Subjected to UV-Ozonation in the 66-Lamp Unit...

The TMS derivative of 4-picolinic acid (isonicotinic acid) was identified in the TMS-treated reaction mixture from the UV-ozonation of paraquat. This suggests a sequence of reactions, in which Slade (10), Funderburk et al, (11), and others have made... 

Figure 4. Products resulting from UV-ozonation of atrazine.

Field studies. Our research with the large UV reactor on the Beltsville Research Farm was directed toward finding the optimal conditions for destroying pesticide wastewater using UV-ozonation. We did not concentrate on the microbial phase at this time, other than in a very limited way. 

Figure 8. Degradation of atrazine at 12000 ppm via UV-ozonation in the 66-lamp unit.

It is difficult to compare costs to other disposal options. The Seiber report ( ) listed the capital cost for incineration at 89,550, and yearly operating cost of 106,500, based on 1978 estimates. The capital and operating costs for our UV-ozonation... 

Figure 9. Effect of concentration on the degradation of formulated atrazine at four concentrations via UV-ozonation in a 450 W medium-pressure mercury vapor lamp.

Figure 10. Effect of gradual increase in concentration up to a concentration of 2356 ppm on the degradation of formulated atrazine up to a concentration of 2356 ppm via UV-ozonation in the 66-lamp unit.

Figure 12. Degradation of paraquat via UV-ozonation at 1500 ppm in the 66-lamp unit.

Fig. 5 Illustration of NIST Gradient UV-Ozone device for generating surface energy libraries on substrates functionalized with hydrophobic SAM species. The sample stage accelerates the specimen blue) beneath a slit-source of UV light. (Reproduced with permission from [12])...

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