(548g) Optimization of Dye Degradation Process By Oxidative Technology

Mayur M. Yenkie*, Pratibha S. Agrawal, M.G.Bhotmange, M.K.N. Yenkie

Department of Chemical Technology, LIT, RTM Nagpur University, Nagpur-444033

Abstract

Background

Increasing population affects the food demand and with the modernization, various food additives are competing in market with each other. Different food flavors and dyes are now a days added for its better presentation. Excess use and disposal of such additives is dangerous for aquatic life. Various conventional methods are used for removal of such dyes which are transferring the contaminant from one phase to another phase only. Wastewater comprised of dyes are hard to treat, since the dyes are recalcitrant organic molecules that are resistant to aerobic digestion and are stable to light, heat and oxidizing agent. The Fenton reaction has been used in industrial wastewater purification [1]. Degradation of different dyes like acidic, reactive, direct, cationic, disperse and vat dyes by the Fenton process was reported [2].

In the present work, degradation of Sunset Yellow under solar, UV and dark Fenton was carried out using different oxidants. The rate of photocatalytic degradation was measured spectroscopically by measuring dye concentration at regular time interval. Optimization of experimental parameters were evaluated for the effective degradation of dye.

Methodology

All chemical were of analytical grade. All experiments were carried out in batch mode in a 1.0 liter jacketed thermostatic photo reactor (diameter 81mm and height 320 mm) equipped with low pressure mercury lamp (8 W, UV-C, manufacture by Philips, Holland) placed axially at its center. The UV lamp was encased in a quartz tube to protect it from direct contact with an aqueous solution flowing through the annulus between the inner surface of the vessel and the outer surface of the quartz tube, located at the axis of the vessel. The reactor was placed over a magnetic stirrer and a teflon coated magnetic needle was used for stirring the solution at the constant rpm using a dimmerstat. All the reactions were performed at atmospheric pressure. Constant reactor temperature was maintained by circulating water from a cryostat bath (Fourtech Systems, Mumbai, India). A gas tight syringe is used to collect the sample at desired intervals from the sample-port of the reactor.

All the stock solutions, standards and pure compounds are stored in dark, below room temperature. The adjustment of pH is made with 0.1 N /1.0N solution of H₂SO₄ or 0.1N/1.0N NaOH. Experiments were carried out in batch mode. For studying the photodegradation of sunset Yellow, the photoreactor was charged with 800 ml of 3x10^-4mol/L solution of the pollutant in deionised water and the required concentrations of iron salt FeCl₃ as a source of Fe(III) were added. A 30% aqueous hydrogen peroxide solution was injected into the reactor at required concentrations and the UV-light was switched on at the same time. The change in pollutant concentration was measured with UV-visible double beam spectrophotometer (Spectrascan UV 2600, Chemito, India). The experimental data is used to study the reaction kinetics of degradation of pollutants.

Results

Comparison among various degradation processes

Solar, fenton and fenton like processes were compared for decreasing the cost of degradation.It has been observed that, the degradation rate is minimum for dark fenton like reaction and solar reaction. In other words, solar light can induce degradation in absence of FeCl3 also. For the same set, rate has been found to be increased to 4X 10 -7, in case of UV assisted degradation. Further addition of Fenton reagent in such a reaction vessel increased rate to ten times. Still highest rate is observed for solar assisted Fenton like reaction.

Conclusion

In this work, the decolorization of SY in aqueous solution by Fenton and Fenton like oxidation process has been studied at different experimental conditions, including pH value of solution, initial concentration of H2O2 and Fe2+ dose, as well as the initial dye concentration. The examined Fenton's reaction was found to be more effective at pH 3.5. The best removal efficiency was achieved for solar assisted Fenton like reaction wheredecolorization efficiency was achieved within 60 min of reaction for initial SY solution of 2x 10-4 Molar. The Kinetic study indicated that the degradation kinetics of SY followed the second-order kinetics

References

[1] N. Klamerth, S. Malato, A. Agüera, and A. Fernández-Alba, “Photo-Fenton and modified photo-Fenton at neutral pH for the treatment of emerging contaminants in wastewater treatment plant effluents: A comparison,” Water Res., vol. 47, no. 2, pp. 833–840, 2013.

[2] X. R. Xu, H. Bin Li, W. H. Wang, and J. D. Gu, “Degradation of dyes in aqueous solutions by the Fenton process,” Chemosphere, vol. 57, no. 7, pp. 595–600, 2004.