Solar detoxification of water containing chlorinated solvents and heavy metals via TiO sub 2 photocatalysis
Researchers around the world have demonstrated the effectiveness of titanium dioxide-based photocatalysis for decontaminating water containing hazardous organics and heavy metals. A great advantage of this process is that the organic is completely destroyed, leaving behind only water, carbon dioxide and dilute mineral acids. Also, the process has potential for doing two decontamination jobs at once: oxidizing organics while reducing toxic metals. As part of a program sponsored by the DOE, Sandia National Laboratories is carrying out large-scale tests to study the solar destruction of organics at realistic processing rates in addition to laboratory work aimed at determining the applicability of solar detoxification to the removal of heavy metals. In this paper, we present up-to-date results from Sandia's effort. The large-scale tests illustrate the effectiveness of solar detoxification for a variety of organics and compare measured reaction rates against published values of the rate constants for attack by aqueous hydroxyl radicals. This comparison highlights the importance of hydroxyl radical chemistry in solar detoxification processes. It is concluded that solar detoxification is only feasible for easily destroyed compounds like TCE, and PCE. The chlorinated methanes and ethanes are much more difficult to destroy and require very large solar collectors. In the second part of the paper, laboratory data are presented for a variety of different metals, including Ag, Cd, Cu, Hg, Ni, and Pt. The concentration of dissolved oxygen is one of the variables in the study. It is shown that the presence of dissolved metals can have a profound effect on organic oxidation rate, and that oxygen is not necessarily required for oxidation to occur. It is concluded that solar detoxification would be useful for removing mercury and silver but not for copper, nickel nor cadmium. 38 refs., 7 figs., 2 tabs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5858147
- Report Number(s):
- SAND-91-1285C; CONF-920436-3; ON: DE91018396
- Resource Relation:
- Conference: 1992 ASME-JSES-KSES international solar energy conference, Maui, HI (United States), 4-8 Apr 1992
- Country of Publication:
- United States
- Language:
- English
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Summary of engineering-scale experiments for the Solar Detoxification of Water project
Destruction of organics and removal of heavy metals in water via TiO{sub 2} photocatalysis
Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
CHLORINATED ALIPHATIC HYDROCARBONS
DECOMPOSITION
MERCURY
REDUCTION
PLATINUM
SILVER
TITANIUM OXIDES
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
NEAR ULTRAVIOLET RADIATION
PHOTOCHEMICAL REACTIONS
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTROMAGNETIC RADIATION
ELEMENTS
HALOGENATED ALIPHATIC HYDROCARBONS
KINETICS
METALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
RADIATIONS
REACTION KINETICS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
ULTRAVIOLET RADIATION
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)
400500 - Photochemistry
540320 - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)