Factors influencing efficiencies of TiO2-sensitised photodegradation. Part 1.—Substituted benzoic acids: discrepancies with dark-adsorption parameters
- 1 January 1990
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions
- Vol. 86 (23), 3935-3941
- https://doi.org/10.1039/ft9908603935
Abstract
Adsorption isotherm data have been determined at 295 K for salicylic (SA), 4-aminobenzoic (ABZA) and 3-chloro-4-hydroxybenzoic (CHBZA) acids onto TiO2 particles suspended in dilute aqueous solution. Good fit is achieved between these dark-adsorption data and linearised isotherm expressions based on competitive adsorption–desorption equilibria involving competition between solute and solvent. Such linear analyses yield values for K, the equilibrium constants, and also for (ns 2)max, the limiting extents of solute adsorption, attainable in competition with the solvent. The latter values do not correspond to occupancy of each surface O—Ti—O site by a single adsorbed solute, but rather indicate that, on average, each adsorbed acid molecule coexists with ca. 40 adsorbed H2O molecules. Concentration dependences predicted for rates of photodegradation of SA, ABZA and CHBZA on the basis of the experimentally determined adsorption parameters, plus an assumption that a pseudo-first-order Langmuir–Hinshelwood-type rate expression applies to TiO2-sensitised photodegradations, differ markedly from initial rates observed for the latter at 297.5 ± 2.5 K. Consideration is given to various mechanistic sources of such discrepancy.This publication has 11 references indexed in Scilit:
- Kinetic studies in heterogeneous photocatalysis. 2. Titania-mediated degradation of 4-chlorophenol alone and in a three-component mixture of 4-chlorophenol, 2,4-dichlorophenol, and 2,4,5-trichlorophenol in air-equilibrated aqueous mediaLangmuir, 1989
- Kinetics studies in heterogeneous photocatalysis. I. Photocatalytic degradation of chlorinated phenols in aerated aqueous solutions over titania supported on a glass matrixThe Journal of Physical Chemistry, 1988
- Isotope-effect evidence for hydroxyl radical involvement in alcohol photo-oxidation sensitized by TiO2 in aqueous suspensionJournal of Photochemistry and Photobiology A: Chemistry, 1988
- Solar-electric water purification using photocatalytic oxidation with TiO2 as a stationary phaseSolar Energy, 1987
- Photooxidation of organic impurities in water using thin films of titanium dioxideThe Journal of Physical Chemistry, 1987
- Surface photochemistry: on the mechanism of the semiconductor photoinduced valence isomerization of hexamethyl Dewar benzene to hexamethylbenzeneThe Journal of Physical Chemistry, 1986
- Photo-oxidation of organic material in aqueous suspensions of titanium dioxideWater Research, 1986
- Surface photochemistryTetrahedron, 1986
- Kinetics of Heterogeneous Photocatalytic Decomposition of Phenol over Anatase TiO2 PowderBulletin of the Chemical Society of Japan, 1985
- Kinetic studies of secondary alcohol photo-oxidation on ZnO and TiO2 at 348 K studied by gas-chromatographic analysisJournal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1981