Green synthesis of bromine by TiO2 heterogeneous photocatalysis and/or ozone: A kinetic study

Elemental bromine is an industrially relevant compound traditionally produced from bromide ions by using chlorine as the oxidizing agent. Problems related to transportation and handling of the corrosive, expensive and toxic chlorine make green synthetic alternatives highly desirable. In this paper the green synthesis of bromine from bromide in aqueous solutions under mild conditions by means of TiO2 photocatalysis and/or ozonation has been investigated from a kinetic point of view. The ozonation in the absence of the photocatalyst follows a first order kinetic with respect to both ozone and bromide. The kinetics of the reactions in the presence of the photocatalyst has been described by means of a Langmuir-Hinshelwood type model and the values of the kinetic constants and of the apparent adsorption constants have been determined. The results obtained constitute the basis for practical applications of this green and novel bromine synthesis and can be used for future reactor engineering and scale up of the process.