title: Microwave-enhanced persulfate oxidation to treat mature landfill leachate.
abstract: Microwave oxidation process (MOP) was evaluated for treatment of landfill leachate. Kinetics of persulfate oxidation in MOP, effects of pH and persulfate doses on fates of derivative organic acids, and the energy cost of MOP were evaluated. The results showed that total organic carbon (TOC) removal of 79.4%, color removal of 88.4%, and UV254 removal of 77.1% were reached at MOP 550 W/85 °C within 30 min. The kinetics of oxidation by MOP followed the first-order reaction. For a given persulfate dose, the reaction rate increased with the microwave power setting (775 W>550 W>325 W>128 W) with reaction rate constants ranging from 10(-5) to 10(-2) min(-1). The adverse effects on reaction rates under higher microwave power settings and high persulfate doses are plausibly caused by excessive persulfate oxidation and self-scavenging termination of free radicals. During the MOP treatment, TOC/COD ratio dropped with time and an 86.7% reduction in TOC/COD ratio after 120 min at pH 7. Oxalic acid was the major derivative and its concentrations were higher under acidic conditions. Malic, lactic, and acetic acids were formed and soon degraded, and the solution pH has an insignificant effect on their fates. The energy cost of MOP (USD$6.03/m(3)) is essentially similar to that of conventional heating oxidation (CHO) (USD$6.10/m(3)).
authors.affiliation: Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Rd., Taipei 106, Taiwan, ROC.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Chou
authors.affiliation: Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Rd., Taipei 106, Taiwan, ROC. Electronic address: sllo@ntu.edu.tw.
authors.forename: Shang-Lien
authors.initials: SL
authors.lastname: Lo
authors.affiliation: Department of Civil and Environmental Engineering, California State University Fullerton, CA 92834, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Kuo
authors.affiliation: Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Rd., Taipei 106, Taiwan, ROC.
authors.forename: Chih-Jung
authors.initials: CJ
authors.lastname: Yeh
mesh_terms: D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry; D008872:Microwaves; D010100:Oxygen / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods; D013431:Sulfates / Q000737:chemistry*; D013696:Temperature; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D013431:Sulfates; D014874:Water Pollutants, Chemical; D019344:Lactic Acid; D007501:Iron; D010100:Oxygen
keywords: Kinetic analysis; Leachate; Microwave oxidation; Organic acid; Persulfate