Kinetics Study of Dye Decolorization by Oxidation in Aqueous and Aqueous Alcohol Medium
- PDF / 403,934 Bytes
- 6 Pages / 595.276 x 790.866 pts Page_size
- 107 Downloads / 222 Views
(0123456789().,-volV)(0123456789().,-volV)
RESEARCH PAPER
Kinetics Study of Dye Decolorization by Oxidation in Aqueous and Aqueous Alcohol Medium Maria Ashfaq1
•
Rehana Saeed1 • Zahida Khalid1 • Afshan Irfan1
Received: 31 March 2020 / Accepted: 30 October 2020 Ó Shiraz University 2020
Abstract The kinetics of oxidation of methylene blue with potassium bromate was investigated by observing decolorization of methylene blue in aqueous, aqueous methanol and aqueous isopropanol solvent system. The rate of reaction was studied as function of concentrations of methylene blue and potassium bromate in acidic medium at temperature 303 and 313 K. The increase in concentration of potassium bromate enhances the rate of decolorization of methylene blue in acidic medium; no significant change in rate was observed with variation of methylene blue. The rate of decolorization was found to be fastest in aqueous methanol compared to aqueous isopropanol and slow in aqueous medium. From the investigation, it was observed the reaction follows pseudo-first-order kinetics. The kinetic data were used to propose the mechanism of reaction. Thermodynamic parameters, enthalpy of activation (DH*), entropy of activation (DS*) and Gibbs free energy of activation (DG*), were also calculated to support kinetic results. Keywords Methylene blue Pseudo-order kinetics Bromated Dielectric constant Thermodynamic parameters
1 Introduction Methylene blue (phenothiazin-5-ium, 3,7-bis(dimethylamino)-,chloride) (MB), an intense blue dye, is watersoluble and has a sharp absorption peak in the visible region of the spectrum (kmax 667.5 nm). It is well known for its staining and sensitizing characteristics in biological reactions (Muthakia and Jonnalagadda 1989; Santus et al. 1983), and it also acts as a catalyst, inhibitor for polymerization and complexing agent in various chemical reactions (Cizek and Studlarova 1984). It is widely used for dying cotton, wool and silk. The color and toxicity it adds to water bodies are very adverse and injurious to the environmental (Saquib et al. 2008; Jain and Shrivastava 2008). Various methods have been adopted to degrade and remove color of dyes from the industrial effluent as & Maria Ashfaq [email protected] & Rehana Saeed [email protected] 1
Department of Chemistry, University of Karachi, Karachi, Pakistan
precipitation, adsorption, reverse osmosis, aerobic and anaerobic treatment, oxidation and reduction, but these methods were found to be time-consuming and ineffective (Olajire and Olajjide 2014). The decolorization of dye from industrial effluent is found to be more effective than degradation because latter produces hazardous free radicals which are again harmful to the environment, while decolorization of dye involves removal of color from the water effluent without producing any harmful product. The decolorization of dye is influenced by many factors such as nature of the solvent, dye, the reactivity of reductant or oxidant, the pH and ionic strength of the reaction medium (Khan et al.
Data Loading...
