Aqueous photochemical reactions of chloride, bromide, and iodide ions in a diode-array spectrophotometer. Autoinhibition in the photolysis of iodide ions

Abstract

The photoreactions of halide ions were studied in water using a diode array spectrophotometer. The triiodide ion has been shown to exert a strong autoinhibitory effect on the reaction.Please check this proof carefully. Our staff will not read it in detail after you have returned it.Translation errors between word-processor files and typesetting systems can occur so the whole proof needs to be read. Please pay particular attention to: tabulated material; equations; numerical data; figures and graphics; and references. If you have not already indicated the corresponding author(s) please mark their name(s) with an asterisk. Please e-mail a list of corrections or the PDF with electronic notes attached -do not change the text within the PDF file or send a revised manuscript. Corrections at this stage should be minor and not involve extensive changes. All corrections must be sent at the same time.Please bear in mind that minor layout improvements, e.g. in line breaking, table widths and graphic placement, are routinely applied to the final version.We will publish articles on the web as soon as possible after receiving your corrections; no late corrections will be made. Please ensure that all queries are answered when returning your proof corrections so that publication of your article is not delayed. The aqueous photoreactions of three halide ions (chloride, bromide and iodide) were studied using a diode array spectrophotometer to drive and detect the process at the same time. The concentration and pH dependences of the halogen formation rates were studied in detail. The experimental data were interpreted by improving earlier models where the cage complex of a halogen atom and an electron has a central role. The triiodide ion was shown to exert a strong inhibiting effect on the reaction sequence leading to its own formation. Assuming a chemical reaction between the triiodide ion and the cage complex interpreted Q3the strong autoinhibition effect. It is shown that there is a real danger of unwanted interference from the photoreactions of halide ions when halide salts are used as supporting electrolytes in spectrophotometric experiments using a relatively high intensity UV light source.

A detailed kinetic study of the direct photooxidation of 2,4,6-trichlorophenol

“…Through the volume change, the number of photons absorbed in unit volume can be influenced and its controlled variation can be used to study the dependence of the reaction rate on the illumination intensity. This fact has been explained previously in several recent publications from our group [23,25,26,29]. The volume of the sample was changed from 1.0 to 3.5 cm 3 in a standard fluorometric cuvette (path length: 1.000 Â 1.000 cm), i.e., the light intensity per volume can be varied by a factor of 3.5.…”

“…The accelerating effect of light on chlorophenol oxidation also implies that their photochemical properties must be thoroughly investigated together with the known intermediates of the process. Recently, experimental techniques were developed for the online monitoring of photochemical processes using diode array spectrophotometers alone or with external light sources [9,[25][26][27][28][29]. These techniques use online monitoring and can yield kinetic data on photoreactions that have very high time resolution and thus be evaluated by up-to-date kinetic analysis methods.…”

“…These techniques use online monitoring and can yield kinetic data on photoreactions that have very high time resolution and thus be evaluated by up-to-date kinetic analysis methods. They facilitated detailed studies on direct photolytic processes [23,29] and photochemically initiated chain reactions [25]. The experience gained in a number of different studies was summarized in a review article a few years ago [26].…”

Photocatalytic performance of highly amorphous titania–silica aerogels with mesopores: The adverse effect of the in situ adsorption of some organic substrates during photodegradation

“…This kinetic curve cannot be simulated by taking into account only the depletion of SA in unhindered parallel photoreactions, i.e. using the widely accepted kinetic approximations (Langmuir-Hinshelwood model) [25,33,43] for the catalyzed process, and the photochemical model [53,54,57] for the uncatalyzed process. In other words, the amount of SA consumed and the drop of reaction rate cannot be described by two parallel pseudo-first-order photoreactions.…”

Kinetics of the autoxidation of sulfur(iv) co-catalyzed by peroxodisulfate and silver(i) ions

“…Diode array spectrophotometers were not used to avoid known problems of photoinitiation by the analyzing light beam. [38][39][40][45][46][47][48] Kinetic experiments were carried out in standard quartz cuvettes (optical path length = 1.000 cm). Constant temperature (25.0 ± 0.1°C) was maintained with an external thermostat and circulating thermal bath.…”