AvaliaÃÃo CinÃtica da Taxa de ReaÃÃo de DegradaÃÃo do Ãcido DicloroacÃtico via tecnologia de oxidaÃÃo avanÃada OzÃnio/UV: um estudo cinÃtico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

With the current level of industrial activity the quantity of pollutants being rejected into the aquatic environment are constantly increasing. The removal of these products through conventional processes such adsorption, filtration, incineration or biological treatment is not always efficacious, since these methods are based on the simple transference of the pollutants from one phase to another with no degradation. Therefore more efficient technologies must be developed. A possible attractive option is based upon the application of advanced oxidation technologies (AOT). These consist of the utilization of chemical species that promote a complete mineralization of the pollutants with, or without, aiding of light UV. In this work the degradation of dichloroacetic acid (DCA) in aqueous solution with direct ozonization and photolytic ozonization (UV 253.7 nm) was sudied. OzÃnio, âin situâ, was generated by a Fischer generator. The kinetics of the process was evaluated using a 105.3 cm3 almost isoactinic teflon type photoreactor with quartz windows. The dichloroacetic acid degradation tests were performed with standard solutions of the acid with initial concentrations in the range of 2.14 x 10-4 to 11.8 x 10-4 mol.L-1, these circulated for 4 hours through a system consisting of an absorption column, the photoreactor and a heat exchanger, in the presence and also in the absence of light UV. During the experiments, samples were taken and the DCA was quantified using ion chromatography and the total organic carbon level established by a Shimadzu. The concentration of ozone was monitored with indigo blue colorimetry. The results showed that for the O3/UV system the rate was not less than 80% in four hours for a solution with an initial DCA concentration of 2.14 x 10-4 mol.L-1. For a solution of 9.05 x 10-4 mol.L-1 the degradation was 52% indicating that for higher concentrations longer retention times are required. For the system operated without light UV, the degradation rate was only 76%. Cleary the use of ozone associated with UV radiation accelerates the degradation of organic species, an is of potential interest for manufactoring industries. The experimental data were fitted to a mechanicists model basead upon the kinetic data and the constants obtained were KLa=1.03 x 10-3 s-1 and kO3,ag = 7.9 x 10-4 s-1

ASSUNTO(S)

engenharia quimica fotorreator radiaÃÃo ultravioleta Ãcido dicloroacÃtico modelagem ozÃnio ozone dichloracetic acid photoreactor coluna de borbulhamento uv radiation bubbling column.

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