Kinetics and Mechanism Study of Chemical Treatment of Methylene Green by Urea |
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Authors: | Ahmed Tehseen Uddin Fahim Azmat Rafia |
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Institution: | 1. Department of Chemistry, University of Karachi, Karachi 75270, Pakistan;2. Fax: 0092‐021‐9261330;3. Department of Chemistry, Jinnah University for Women, Nazimabad, Karachi, Pakistan |
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Abstract: | The kinetics and mechanism studies, for the reduction of methylene green (MG) by urea, in acidic and alkali media, were studied at λmax=652.8 nm by monitoring the depletion in MG concentration. The reaction was carried out by UV radiation, with variable dye concentration, reducing agent (urea), acid and base under different additive ions that are very common in dye waste water. The reduction followed pseudo first‐order kinetics with respect to different anions, cations, dye, reductant and OH? ion concentrations. It was found that most of the cations tested showed the inhibitory effect on dye decoloration, due to the formation of insoluble precipitate and followed the order K+>Na+>Al3+>Ca2+≈Mg2+. Tested anions showed that the dye decoloration was significantly accelerated and followed the order Cl?>Br?>I?>NO?3>SO2?4. A mechanistic model involving generation of a complex of dye with ions was proposed. |
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Keywords: | methylene green (MG) urea additive ion precipitation OH− ion decoloration |
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