Kinetic modelling of the hematin catalysed decolorization of Orange II solutions.

CECILIA CABRERA; ANDRÉS CORNAGLIA; AGOSTINA CÓRDOBA; IVANA MAGARIO; MARIA LUJAN FERREIRA

CHEMICAL ENGINEERING SCIENCE

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2016 vol. 161 p. 127 - 137

0009-2509

A mathematical description of the kinetics of the hematincatalyseddecolourization reaction of Orange II alkaline solutions wasconstructed and validated under the assumption that hematin mimics theaction of peroxidases. The clean oxidant H2O2 was applied, however,hematin dismutated it, as catalases do, under reaction conditions. Thus,special attention was cared to the understanding of this ineffectiveside-reaction by the proposal of straightforward pathways concerning thecatalatic or the pseudo-catalatic cycles. Model validations wereimplemented by a parametrization procedure of relevant rate constantsunder dynamic simulation fitting to selected experimental time-coursesdata. The peroxidatic coupled to pseudo-catalatic mechanism gavepredictions closer to experimental findings in a wide range ofconditions. The initial rate method for data processing was successfullyapplied for providing reliable initial rate constant guesses but also forthe detection of unexpected rate depletion at high dye concentrations.This was considered in the model as unproductive dye coordination tohematin native state prior to H2O2 activation. The pseudo-catalaticpathway involves the production of superoxide and its coordination tohematin native state to afford inactive but regenerable ferrousporphyrin. Model underestimations of experimental data were interpretedas cooperative oxidation of Orange II molecules by superoxide whereasmodel deviations at high dye concentration (> 400 mg/l) was assigned tofurther hematin catalysed oxidation of Orange II degraded products.