Artículos de revistas
Competitive kinetics versus stopped flow method for determining the degradation rate constants of steroids by ozonation.
Autor
ALBERTO LOPEZ LOPEZ
VALENTIN FLORES PAYAN
ELIZABETH LEON BECERRIL
LEONEL HERNANDEZ MENA
RAMIRO VALLEJO RODRIGUEZ
Institución
Resumen
"Steroids are classified as endocrine disrupting chemicals; they are persistent with low
biodegradability and are hardly degraded by conventional methods. Ozonation process
has been effective for steroids degradation and the determination of the kinetics
is a fundamental aspect for the design and operation of the reactor. This study assessed
two methods: competitive kinetics and stopped flow, for determining the degradation
kinetics of two steroids, estradiol (E2) and ethinylestradiol (EE2) in spiked water.
Experiments were performed at pH 6, 21 °C, and using tertbutyl alcohol as scavenger
of hydroxyl radicals; competitive kinetics method used sodium phenolate as reference
compound. For the stopped flow, the experiments were performed in a BioLogic SFM-
3000/S equipment. For both methods, the second order rate constants were in the
order of 106 and 105 M−1 s−1 for E2 and EE2 respectively. The competitive kinetics can
be applied with assurance and reliability but needing an additional analysis method
to measure the residual concentrations. Stopped flow method allows the evaluation
of the degradation kinetics in milliseconds and avoids the use of additional analytical
methodologies; this method allows determining the reaction times on line. The methods
are applicable for degradation of other emerging contaminants or other steroids
and could be applied in water treatment at industrial level. Finally, it is important to
consider the resources available to implement the most appropriate method, either
competitive kinetics or the stopped-flow method".
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