Photolysis of chloroform and other organic molecules in aqueous TiO sub 2 suspensions

Journal Article · Thu Feb 28 23:00:00 EST 1991 · Environmental Science and Technology; (USA)

DOI:https://doi.org/10.1021/es00015a018· OSTI ID:5555899

Kormann, C; Bahnemann, D W; Hoffmann, M R ^[1]

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1. California Insitute of Technology, Pasadena (USA)

The photocatalytic degradation of chloroform has been investigated in aqueous suspensions of TiO{sub 2} over the wavelength range of 310-380 nm. A detailed reaction mechanism has been proposed in which the rate-determining step is the reaction of surface-bound {sup {sm bullet}}OH with adsorbed CHCl{sub 3}. A pH-stat titration technique was developed for the measurement of the rates of degradation of chlorinated hydrocarbons. The quantum efficiency ({Phi} = 0.56 at {lambda} = 330 nm) of the degradation of CHCl{sub 3} was found to be inversely proportional to the square root of the incident light intensity. This relationship can be explained in terms of a direct competition between a second-order recombination of surface-bound {sup {sm bullet}}OH and the rate-determining reaction of surface-bound {sup {sm bullet}}OH with CHCl{sub 3}. The rates of degradation of several electron donors have been correlated with their computed surface speciation. The results of this study show that the adsorption of electron donors and acceptors to the TiO{sub 2} surface plays a more important role in determining the rate of the photocatalytic reactions than the effect of pH-dependent Fermi-level shifts.

• OSTI ID: 5555899
• Journal Information: Environmental Science and Technology; (USA), Journal Name: Environmental Science and Technology; (USA) Vol. 25:3; ISSN ESTHA; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
54 ENVIRONMENTAL SCIENCES
540320 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
AQUEOUS SOLUTIONS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
CHLOROFORM
DATA ANALYSIS
DECOMPOSITION
DISPERSIONS
EFFICIENCY
ENERGY LEVELS
FERMI LEVEL
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROXYL RADICALS
MIXTURES
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
QUANTUM EFFICIENCY
RADICALS
SOLUTIONS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS