title: Accelerated redox reaction between chromate and phenolic pollutants during freezing.
abstract: The redox reaction between 4-chlorophenol (4-CP) and chromate (Cr(VI)) (i.e., the simultaneous oxidation of 4-CP by Cr(VI) and reduction of Cr(VI) by 4-CP) in ice (i.e., at -20°C) was compared with the corresponding reaction in water (i.e., at 25°C). The redox conversion of 4-CP/Cr(VI), which was negligible in water, was significantly accelerated in ice. This accelerated redox conversion of 4-CP/Cr(VI) in ice is ascribed to the freeze concentration effect occurring during freezing, which excludes solutes (i.e., 4-CP and Cr(VI)) and protons from the ice crystals and subsequently concentrates them in the liquid brine. The concentrations of Cr(VI) and protons in the liquid brine were confirmed by measuring the optical image and the UV-vis absorption spectra of cresol red (CR) as a pH indicator of frozen solution. The redox conversion of 4-CP/Cr(VI) was observed in water when the concentrations of 4-CP/protons or Cr(VI)/protons increased by 100/1000-fold. These results corroborate the freeze concentration effect as the reason for the accelerated redox conversion of 4-CP/Cr(VI) in ice. The redox conversion of various phenolic pollutants/Cr(VI) and 4-CP/Cr(VI) in real wastewater was successfully achieved in ice, which verifies the environmental relevance and importance of freezing-accelerated redox conversion of phenolic pollutants/Cr(VI) in cold regions.
authors.affiliation: Department of Environmental Sciences and Biotechnology, Hallym University, Chuncheon, Gangwon-do 24252, Korea.
authors.forename: Jinjung
authors.initials: J
authors.lastname: Ju
authors.affiliation: Department of Environmental Sciences and Biotechnology, Hallym University, Chuncheon, Gangwon-do 24252, Korea.
authors.forename: Jaesung
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Chemistry and Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.
authors.forename: Ľubica
authors.initials: Ľ
authors.lastname: Vetráková
authors.affiliation: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Seo
authors.affiliation: Department of Chemistry and Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.
authors.forename: Dominik
authors.initials: D
authors.lastname: Heger
authors.affiliation: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.
authors.forename: Changha
authors.initials: C
authors.lastname: Lee
authors.affiliation: Korea Polar Research Institute (KOPRI), Incheon 21990, Korea.
authors.forename: Ho-Il
authors.initials: HI
authors.lastname: Yoon
authors.affiliation: Korea Polar Research Institute (KOPRI), Incheon 21990, Korea. Electronic address: ktkim@kopri.re.kr.
authors.forename: Kitae
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Environmental Sciences and Biotechnology, Hallym University, Chuncheon, Gangwon-do 24252, Korea. Electronic address: jwk@hallym.ac.kr.
authors.forename: Jungwon
authors.initials: J
authors.lastname: Kim
keywords: Chromate; Freeze concentration effect; Ice; Phenolic pollutants; Redox reaction