Photochemical oxidation of methyldiethanolamine (MDEA) in aqueous solution by UV/K2S2O8 process

International Journal of Industrial Chemistry, Feb 2016

Methyldiethanolamine (MDEA) as an organic material is a hazardous contaminant in the aquatic environment because of its adverse effects on aquatic life, environment, and humans. In this study, a batch reactor of ultraviolet (UV) light and peroxydisulfate was performed to investigate the degradation of MDEA in aqueous media. The effect of different experimental parameters such as UV irradiation, peroxydisulfate concentration, MDEA concentration, temperature, and solution pH on removal of MDEA was evaluated precisely. No significant degradation was observed with a separate UV light. Adding peroxydisulfate to the solution increased the removal performance more than 75 %.

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Photochemical oxidation of methyldiethanolamine (MDEA) in aqueous solution by UV/K2S2O8 process

Int J Ind Chem Photochemical oxidation of methyldiethanolamine (MDEA) in aqueous solution by UV/K2S2O8 process G. Samira Molareza 0 1 2 Mojtaba Ahmadi 0 1 2 A. A. Zinati Zadeh 0 1 2 0 Applied Chemistry Department, Faculty of Chemistry, Razi University , Kermanshah , Iran 1 Chemical Engineering Department, Faculty of Engineering, Razi University , Kermanshah , Iran 2 & Mojtaba Ahmadi Methyldiethanolamine (MDEA) as an organic material is a hazardous contaminant in the aquatic environment because of its adverse effects on aquatic life, environment, and humans. In this study, a batch reactor of ultraviolet (UV) light and peroxydisulfate was performed to investigate the degradation of MDEA in aqueous media. The effect of different experimental parameters such as UV irradiation, peroxydisulfate concentration, MDEA concentration, temperature, and solution pH on removal of MDEA was evaluated precisely. No significant degradation was observed with a separate UV light. Adding peroxydisulfate to the solution increased the removal performance more than 75 %. Peroxydisulfate; MDEA; Advanced oxidation processes; Wastewater treatment Introduction Raw natural gas includes some acidic gases such as H2S and CO2. These acidic gases are very corrosive and toxic to the environment, and therefore required to be removed. Different alkanolamines such as monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) and diisopropanolamine (DIPA) are used for the removal of acidic gases in the sweetening gas units [ 1 ]. In addition N-methyldiethanolamine (MDEA) as metalMDEA complexes have as propertysignificant ultraviolet (UV) absorption. New photosensitive precursors was prepared as thin films by N-methyldiethanolamine complex [ 2, 3 ]. Usually during cleaning, protecting and scheduled control of absorption and desorption column, high concentration of alkanolamine is generated into the wastewater [4]. Nevertheless, due to its toxicity the conventional biological treatment cannot be used for this wastewater [ 5 ]. During recent two decades, advanced oxidation processes (AOPs) have been considered as popular techniques to treat the high concentration of organic contaminant in the wastewater [ 6 ]. AOPs are of the most alternative techniques for destruction of many other organic matters in wastewater and effluents. These processes generally involve UV/H2O2, UV/O3, UV/S2O82- or UV/Fenton’s reagent for degradation of contaminants [ 7–9 ]. A large number of experimental works have been performed on the application of AOPs to treat wastewater. The Fenton’ reagent in the AOPs was used to degrade MEA [ 10 ], DEA [ 11 ], N,N-diethyl-p-phenylenediamine [ 12 ] and DIPA [ 13 ]. Also, the use of UV/H2O2 in the AOPs for degradation of MEA and MDEA [ 4, 14 ] and ozonation for degradation of DEA [15] have been studied. Because of its high reactivity of UV/S2O82- process, high solubility, relatively low cost of peroxydisulfate and benign end products, recently the application of UV/ S2O82- in wastewater treatment was investigated in numerous studies [ 16 ]. Peroxydisulfate (S2O82-) is a strong oxidant (E0 = 2.05 V) which has been used widely in the petroleum industry for the treatment of hydraulic fluids or as a reaction initiator [ 17 ]. It has also been reported to be effective for degrading organic matters in hazardous wastewaters in acidic or basic media through direct chemical oxidation, where peroxydisulfate is used as a sacrificial reagent [ 17–19 ]. However, since the reactions of peroxydisulfate are generally slow at normal temperature. The thermal or photochemical activated decomposition of S2O82- ion to SO4- radical has been proposed as a method of accelerating the process [ 19, 20 ], as summarized in the following reactions (Eqs. 1–12): 2 hv=heat S2O8 ! 2SO4 SO4 þ RH2 ! SO24 þ Hþ þ RH 2 RH þ S2O8 ! R þ SO24 þ Hþ þ SO4 SO4 þ RH ! R þ SO24 þ Hþ 2R ! RRðdim erÞ SO4 þ H2O ! HSO4 þ OH ð500 60 S 1Þ HSO4 ! Hþ þ SO24 2 OH þ S2O8 SO4 þ OH 1 ! HSO4 þ SO4 þ 2 O2 1 ! HSO4 þ 2 O2 2OH ! H2O2 ðexpect in alkaline solutionÞ 1 H2O2 ! H2O þ 2 O2 ðmostly in acidic solutionÞ S2O8 þ H2O2 ! 2Hþ þ 2SO24 þ O2 2 ð1Þ ð2Þ ð3Þ ð4Þ ð5Þ ð6Þ ð7Þ ð8Þ ð9Þ ð10Þ ð11Þ ð12Þ As can be seen in the above reactions, the oxidation process is begun by production of the sulfate and hydroxyl radicals (Eqs. 1 and 2). These radicals are powerful oxidizing agents which may attack the organic matters (R) in the contaminated water. It causes, ultimately, complete decomposition of toxic and bioresistant compounds to harmless species (like CO2, H2O, etc.). Sulfate ion will be generated as the end product, which is practically inert and is not considered to be a pollutant. It is worth to mention that the United States Environmental Protection Agency (USEPA) has listed SO42- under the secondary drinking water standards. A maximum concentration of sulfate ion is 250 mg l-1 (1.43 mM), based on sanitary reasons such as taste and odor [ 1 (...truncated)


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G. Samira Molareza, Mojtaba Ahmadi, A. A. Zinati Zadeh. Photochemical oxidation of methyldiethanolamine (MDEA) in aqueous solution by UV/K2S2O8 process, International Journal of Industrial Chemistry, 2016, pp. 1-8, Volume 7, Issue 1, DOI: 10.1007/s40090-016-0071-2