Kinetics Of Sorption Of Cr((vi)-diphenylcarbazide Complex On Ku-2-8 Cation Exchanger
KINETICS OF SORPTION OF Cr((VI)-DIPHENYLCARBAZIDE COMPLEX ON KU-2-8 CATION EXCHANGER
A. N. Chebotaryov, T. M. Shcherbakova, E. M. Guzenko
I.I. Mechnikov Odessa State University, Department of Analytical Chemistry, Odessa, Ukraine
Cr(VI) is one of high-toxic elements (its maximum permissible concentration (MPC) is 0.05 mg/l) which content in aqueous media must be controlled. A spectrophotometric reaction of Cr(VI) with 1,5-diphenylcarbazide (DPC) is sufficiently selective and allows to determine CCr(VI) at the MPC level. One of perspective tendencies in the monitoring of toxic-element content in waters is the development of rapid and selective test methods combining the sorption concentrating in the dynamic regime with the visual colorimetric determination. Kinetic investigations of the sorption process are of great importance for the development of such test methods.
In the work, the results of the study of the Cr(VI)-DPC-complex adsorption from aqueous solutions with different concentrations of the complex (0.1 to 0.2 mg/l), volumetric rates of the solution flow (0.31 to 15.65ml/min), and residence times of the solution in the sorbent phase (0.167-1 min) are presented. Analyzing the outlet adsorption-diagrams at different solution volumetric rates, two types of the dynamic curves have been found: with one or two plateaus. They are evidence of differences in the space location of the complex molecules relative to the support surface as well as in the quantitative sorption characteristics. The optimal conditions for the sorption in the investigated system as well as the factor of the sorption process have been found. The plot of the latter as a function of the residence time confirms the suggested mechanism of the sorption extraction studied at different volumetric rates of the complex solution passing through a bed of the sorbent.
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