title: Elimination of microcystin-LR and residual Mn species using permanganate and powdered activated carbon: Oxidation products and pathways.
abstract: The oxidation of microcystin-LR (MC-LR) in deionized water (DI) and river water using potassium permanganate (KMnO4) at a neutral pH and at 23 ± 2 °C was investigated. These two aqueous systems (i.e., DI and river water) gave comparable second-order rate constants (289.9 and 285.5 M-1s-1(r2> 0.99), respectively), which confirmed the effectiveness of this oxidation process for the treatment of natural surface water. The presence of either humic or fulvic acid reduced the removal efficiency of MC-LR, with the latter exhibiting a greater inhibitory effect. Monitoring of MC-LR and residual Mn2+levels with adding KMnO4(1 mg/L) and powdered activated carbon (PAC, 5-20 mg L-1) before and during coagulation, respectively, revealed that 60 min of permanganate pre-oxidation followed by coagulant addition with PAC was the most effective approach for reducing both levels below limits stated by WHO guidelines. The MC-LR degradation products were the result of oxidation occurring at the diene and aromatic moieties of the Adda (3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid) side-chain, in addition to amine bond hydrolysis of the Mdha (N-methyldehydroalanine) moiety. Several toxic by-products with an intact Adda chain were observed during the reaction, but completely disappeared after 60 min. This further supports the conclusion that sufficient contact time with permanganate (i.e., >60 min) is essential to reducing the residual toxicity and maximizing the efficiency of MC-LR oxidation when treating raw water.
authors.affiliation: Center for Water Resources Cycle Research, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul, 02792, Republic of Korea.
authors.forename: Boyoung
authors.initials: B
authors.lastname: Jeong
authors.affiliation: Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul, 02792, Republic of Korea.
authors.forename: Min-Seok
authors.initials: MS
authors.lastname: Oh
authors.affiliation: Advanced Analysis Center, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul, 02792, Republic of Korea.
authors.forename: Hyun-Mee
authors.initials: HM
authors.lastname: Park
authors.affiliation: Center for Water Resources Cycle Research, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul, 02792, Republic of Korea.
authors.forename: Chanhyuk
authors.initials: C
authors.lastname: Park
authors.affiliation: Center for Water Resources Cycle Research, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul, 02792, Republic of Korea; Energy and Environmental Engineering, Korea University of Science and Technology, Seoul, 02792, Republic of Korea. Electronic address: eunjukim@kist.re.kr.
authors.forename: Eun-Ju
authors.initials: EJ
authors.lastname: Kim
authors.affiliation: Center for Water Resources Cycle Research, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul, 02792, Republic of Korea; Energy and Environmental Engineering, Korea University of Science and Technology, Seoul, 02792, Republic of Korea. Electronic address: swhong@kist.re.kr.
authors.forename: Seok Won
authors.initials: SW
authors.lastname: Hong
mesh_terms: D002606:Charcoal; D005618:Fresh Water / Q000737:chemistry; D052998:Microcystins / Q000737:chemistry*; D010084:Oxidation-Reduction; D011196:Potassium Permanganate; D018508:Water Purification
chemical_list: D052998:Microcystins; D011196:Potassium Permanganate; D002606:Charcoal
keywords: Microcystin-LR; Natural organic matter; Oxidation by-product; Oxidation pathway; Potassium permanganate; Powdered activated carbon