Study of the interaction of ozone with phenantroline for the determination of the oxidation kinetic of iron (II) with a FIA system
Advancing the chemical engineering fundamentals
Catalysis (T2-13P)
Keywords: ozone; iron; FIA; kinetic; phenantroline
Electroplating wastewaters are characterized for high concentrations of iron (II) up to 20g/100 ml. The removal of this pollutant in wastewaters is desirable for reasons of protecting wastewater treatment systems. Iron can be eliminated by oxidation followed by precipitation or absorption. This preoxidation treatment can be done by bubbling ozone in a G/L reactor due to this gas is capable of oxidize iron (II) to iron (III) (1). In order to study the kinetic of this process it is convenient an automated process for the on-line measurement of the variation in concentration of the dissolved ferrous ions in the solution. One of the most popular methods for the determination of iron is the measurement of the absorbance of Fe(II) - 1,10-phenanthroline complex (2). This method can be combined with FIA system, which makes possible to carry out a large number of determinations with a minimum consumption of samples and reagents (3).
The aim of this work has been the preliminary study of the kinetic process when ozone is used to oxidize Fe(II) to Fe(III) in a G/L reactor and the proposal of an experimental set-up for the determination of the different substances involved in the reaction. Experiments to study the effect of temperature, ozone gas concentration, and the interaction between ozone+phenantronile and ozone+complex Fe and phenetroline has been done.
For the experiments a G/L reactor of 0.5 L capacity has been used. Ozone has been produced with a Multiozono generator. Solutions of iron (II) have been prepared with ultra pure water using Mohr’s salt (Merck). Phenantroline has been used as chelating agent (Merck). The absorption spectra have been measured with a Diode Array Multispec-1501 (Shimazdu).
Results of ozonation of a phenantroline solution show that ozone is not consumed during the experiment so oxidation rate of ozone+phenantroline is insignificant or null. Kinetic experiments with and without iron-phenantroline complex in the G/L reactor show that the presence of phenantroline decreases significantly the oxidation rate of iron (II) to iron (III). There have not been appreciated any effects in the kinetic of the reaction in the range of temperatures studied. The analysis of absorption spectra of a non complexed iron solution during the ozonation experiments shows that a peak at 303 nm appears as the oxidation occurs, reaching a maximum when the ozonation is completed. This peak has been associated to the presence of Iron (III) in the solution.
The authors gratefully acknowledge the Conselleria d’Empresa, Universitat i Ciència de la Generalitat Valenciana for financial support of this work under project ref. GV06/083.
(1) Reckhow, D.A., Knocke, W.R., Kearney, M.J. and Parks, C.A., Oxidation of Iron and Manganeso by Ozone; Ozone Science and Engineering, 13, 675-695 (1991)
(2) Radionova, T.V:, Beklemishev, M.K., Dracheva, L.V. and Zolotov, Y.A., Continuous Flow Analysis Determination of Iron in Industrial Solutions; Journal of Analytical Chemistry, 47 (7), 888 -892 (1992).
(3) Mortatti, J., Drug, F.J., Pessenda, L.C.R., Zagatto, E.A.G., Determination of Iron in Natural Waters and Plant Material with 1,10-Phenantroline by Flow Injection Analysis; Analyst, 107, 659-663 (1982).
Presented Wednesday 19, 13:30 to 15:00, in session Catalysis (T2-13P).
