3 research outputs found

    Kinetic modeling based on the non-linear regression analysis for the degradation of Alizarin Red S by advanced photo Fenton process using zero valent metallic iron as the catalyst

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    The degradation of Alizarin Red S (ARS), an anthraquinone dye was investigated by advanced photo Fenton process using zero valent metallic iron (ZVMI) powder as the catalyst with symmetrical peroxides like hydrogen peroxide (HP)/ammonium persulfate (APS) as the oxidants. APS is proved to be a better oxidant compared to HP as it provides efficient acidic medium which is critical for Fenton process. A kinetic/mathematical model was developed based on the non-linear regression analysis and the validity of the model was tested by comparing the observed experimental values with the theoretically calculated data. The rate equation obtained was found to be a function of iron dosage, oxidant and dye concentration at pH 3.k = 0.2456 Fe 0.21 APS 0.15 ARS - 0.76k = 0.58 Fe 0.12 HP 0.10 ARS - 0.86. The degradation pathway was followed by UV-vis spectroscopy and GC-MS techniques. Based on the intermediates analyzed, a probable degradation mechanism has been proposed. © 2009 Elsevier B.V. All rights reserved

    Degradation mechanism of diazo dyes by photo-Fenton-like process: Influence of various reaction parameters on the degradation kinetics

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    The degradation of diazo dyes Brilliant Yellow (BY) and Bismark Brown (BB) was investigated by the photo-Fenton-like process Fe2+/aminonium persulphate (APS)/UV in acidic pH medium. The influence of various reaction parameters like pH, concentration of Fe2+ ions/APS, structure of the dye and effect of radical scavenger on the degradation kinetics is reported. The rate constant (k), catalytic efficiency (kc) and process efficiency (Φ) are evaluated at different concentrations of Fe2+ ions. It was found out that the BB degrades at a faster rate than BY. The degradation process was followed by GC-MS technique. The results show that the initial step in the degradation of BB involves direct oxidation of azo chromophore, while in the case of BY the initial step is oxidation of azo group followed by the oxidation of ethylenic chromophore. Based on the obtained intermediates, probable degradation mechanism has been proposed. The results show that photo-Fenton-like process could be a useful and efficient technology for the mineralization of diazo dyes at lower concentrations of iron in acidic medium. © 2009 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria

    Photo-Fenton and photo-Fenton-like processes for the degradation of methyl orange in aqueous medium: Influence of oxidation states of iron

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    Degradation of methyl orange (MO) was carried out by the photo-Fenton process (Fe2+/H2O2/UV) and photo-Fenton-like processes (Fe3+/H2O2/UV, Fe2+/S2O8 2-/UV, and Fe3+/S2O8 2-/UV) at the acidic pH of 3 using hydrogen peroxide and ammonium persulfate (APS) as oxidants. Oxidation state of iron had a significant influence on the efficiency of photo-Fenton/photo-Fenton-like processes. It was found that a process with a source of Fe3+ ions as the catalyst showed higher efficiency compared to a process with the Fe2+ ion as the catalyst. H2O2 served as a better oxidant for both oxidation states of iron compared to APS. The lower efficiency of APS is attributed to the generation of excess protons which scavenges the hydroxyl radicals necessary for degradation. Further, the sulfate ions produced from S2O8 2- form a complex with Fe2+/Fe3+ ions thereby reducing the concentration of free iron ions in the solution. This process can also reduce the concentration of hydroxyl radicals in the solution. Efficiency of the various MO degradation processes follows the order: Fe3+/H2O2/UV, Fe3+/APS/UV, Fe2+/H2O2/UV, Fe2+/APS/UV. © 2009 Institute of Chemistry, Slovak Academy of Sciences