Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/96249
標題: Oxidative polymerization reactions of hydroquinone and chromium(VI) in an aqueous solution
對苯二酚與六價鉻在水溶液中之氧化聚合反應
作者: Ching-Yun Cheng
鄭靜芸
關鍵字: 氧化聚合
對苯二酚
對苯醌
六價鉻
過氧化氫
類腐植物質
oxidative polymerization
hydroquinone
1,4-benzoquinone
chromium(VI)
hydrogen peroxide
humic-like substances
引用: Ahalya, N., R.D. Kanamadi, and T.V. Ramachandra. 2005. Biosorption of chromium(VI) from aqueous solutions by the husk of Bengal gram (Cicer arientinum). Electron. J. Biotechnol. 8: 258-264. Ahamad, T., N. Nishat, and S. Parveen. 2008. Synthesis, characterization and anti-microbial studies of a newly developed polymeric Schiff base and its metal-polychelates. J. Coord. Chem. 61: 1963-1972. Aiken, G.R., D.M. McKnight, R.L. Wershaw, and P. MacCarthy. 1985. Humic substances in soil, sediment, and water: geochemistry, isolation and characterization. John Wiley & Sons, New York, USA. Albarran, G. and R.H. Schuler. 2008. Determination of the spectroscopic properties and chromatographic sensitivities of substituted quinones by hexachlorate(IV) oxidation of hydroquinones. Talanta 74: 844-850. Amir, S., A. Jouraiphy, A. Meddich, M. El Gharous, P. Winterton, and M. Hafidi. 2010. Structural study of humic acids during composting of activated sludge-green waste: elemental analysis, FTIR and 13C NMR. J. Hazard. Mater. 177: 524-529. Amonette, J.E. and D. Rai. 1990. Identification of noncrystalline (Fe, Cr)(OH)3 by infrared spectroscopy. Clay Clay Miner. 38: 129-136. Anderson, H.A., W. Bick, A. Hepburn, and M. Stewart. 1989. Nitrogen in Humic Substances. Humic Substances II: In Search of Structure. John Wiley & Sons, New York, USA. Arakawa, H., M.W. Weng, W.C. Chen, and M.S. Tang. 2012. Chromium(VI) induces both bulky DNA adducts and oxidative DNA damage at adenines and guanines in the p53 gene of human lung cells. Carcinogenesis 33: 1993-2000. ATSDR. 2017. Priority List of Hazardous Substances. Division of Toxicology, Department of Health and Human Services, USA. Bassett, J. 2013. Inorganic chemistry: a concise text. Pergamon press, London, UK, pp. 294-296. Belzile, N., H.A. Joly, and H. Li. 1997. Characterization of humic substances extracted from Canadian lake sediments. Can. J. Chem. 75: 14-27. Bielicka, A., I. Bojanowska, and A. Wisniewski. 2005. Two Faces of Chromium- Pollutant and Bioelement. Pol. J. Environ. Stud. 14: 5-10. Blasco, J., J.M. Michalik, J. García, G. Subías, and J.M. De Teresa. 2007. Effects of the lanthanide addition to the Sr2CrReO6 double perovskite. Phys. Rev. B 76: 144402. Campitelli, P.A., M.I. Velasco, and S.B. Ceppi. 2006. Chemical and physicochemical characteristics of humic acids extracted from compost, soil and amended soil. Talanta 69: 1234-1239. Cao, X.H., J. Guo, J.D. Mao, and Y.Q. Lan. 2011. Adsorption and mobility of Cr(III)–organic acid complexes in soils. J. Hazard. Mater. 192: 1533-1538. Chang, R.R., S.L. Wang, Y.T. Liu, Y.T. Chan, J.T. Hung, Y.M. Tzou, and K.J. Tseng. 2016. Interactions of the products of oxidative polymerization of hydroquinone as catalyzed by birnessite with Fe (hydr)oxides–an implication of the reactive pathway for humic substance formation. RSC Adv. 6: 20750-20760. Chattopadhyay, B., S. Datta, and A. Chatterjee. 2000. The environmental impact of waste chromium of tannery agglomerates in the East Calcutta wetland ecosystem. J. Soc. Leather Technol. Chem. 84: 94-100. Chauhan, A., S. Samanta, and R. Jain. 2000. Degradation of 4‐nitrocatechol by Burkholderia cepacia: a plasmid‐encoded novel pathway. J. Appl. Microbiol. 88: 764-772. Chen, J.K., C.H. Yeh, L.C. Wang, T.H. Liou, C.R. Shen, and C.L. Liu. 2011. Chitosan, the marine functional food, is a potent adsorbent of humic acid. Mar. Drugs 9: 2488-2498. Cheng, C.Y., Y.T. Chan, Y.M. Tzou, K.Y. Chen, and Y.T. Liu. 2016. Spectroscopic investigations of the oxidative polymerization of hydroquinone in the presence of hexavalent chromium. J. Spectrosc. 2016: Article ID 7958351. Chin, Y.P., G.R. Aiken, and K.M. Danielsen. 1997. Binding of pyrene to aquatic and commercial humic substances: the role of molecular weight and aromaticity. Environ. Sci. Technol. 31: 1630-1635. Cotton, F.A. and G. Wilkinson. 1980. Advanced inorganic chemistry: a comprehensive text. John Wiley & Sons, New York, USA. Dadzie, O.E. and A. Petit. 2009. Skin bleaching: highlighting the misuse of cutaneous depigmenting agents. J. Eur. Acad. Dermatol. Venereol. 23: 741-750. Das, L., M. Dutta, and J.K. Basu. 2013. Photocatalytic degradation of phenol from industrial effluent using titania-zirconia nanocomposite catalyst. Int. J. Environ. Sci. 4: 415-431. Daulton, T.L., B.J. Little, K. Lowe, and J. Jones-Meehan. 2001. In situ environmental cell–transmission electron microscopy study of microbial reduction of chromium(VI) using electron energy loss spectroscopy. Microsc. Microanal. 7: 470-485. Davis, A. and R.L. Olsen. 1995. The geochemistry of chromium migration and remediation in the subsurface. Groundwater 33: 759-768. De Groot, F., G. Vankó, and P. Glatzel. 2009. The 1s x-ray absorption pre-edge structures in transition metal oxides. J. Phys.: Condens. Matter 21: 104207. De Paolis, F. and J. Kukkonen. 1997. Binding of organic pollutants to humic and fulvic acids: influence of pH and the structure of humic material. Chemosphere 34: 1693-1704. Dellinger, B., W.A. Pryor, R. Cueto, G.L. Squadrito, V. Hegde, and W.A. Deutsch. 2001. Role of free radicals in the toxicity of airborne fine particulate matter. Chem. Res. Toxicol. 14: 1371-1377. Demiral, H., I. Demiral, F. Tümsek, and B. Karabacakoğlu. 2008. Adsorption of chromium (VI) from aqueous solution by activated carbon derived from olive bagasse and applicability of different adsorption models. Chem. Eng. J. 144: 188-196. Dermatas, D., C. Vatseris, I. Panagiotakis, and M. Chrysochoou. 2012. Potential contribution of geogenic chromium in groundwater contamination of a Greek heavily industrialized area. Chem. Eng. Trans. 28: 217-222. Dobos, D. 1975. A handbook for electrochemists in industry and universities. Elsevier. dos Santos, A.J., D.K. de Souza Xavier, D.R. da Silva, M. Antonio Quiroz, and C.A. Martinez-Huitle. 2014. Use of combined electrochemical approaches for mineralization and detection of hydroquinone using PbO2 electrodes. J. Mex. Chem. Soc. 58: 356-361. Dupont, L., E. Guillon, J. Bouanda, J. Dumonceau, and M. Aplincourt. 2002. EXAFS and XANES studies of retention of copper and lead by a lignocellulosic biomaterial. Environ. Sci. Technol. 36: 5062-5066. Eash, N.S., T.J. Sauer, D. O'Dell, and E. Odoi. 2015. Soil science simplified. John Wiley & Sons, New York, USA, pp. 35-38. Elzinga, E.J. and A. Cirmo. 2010. Application of sequential extractions and X-ray absorption spectroscopy to determine the speciation of chromium in Northern New Jersey marsh soils developed in chromite ore processing residue (COPR). J. Hazard. Mater. 183: 145-154. Emsley, J. 2011. Nature's building blocks: an AZ guide to the elements. Oxford University Press, New York, USA, pp. 111-114. Enev, V., L. Pospisilova, M. Klucakova, T. Liptaj, and L. Doskocil. 2014. Spectral Characterization of Selected Humic Substances. Soil Water Res. 9: 9-17. Evans, K.A., H.S.C. O'Neill, J.A. Mavrogenes, N.S. Keller, L.Y. Jang, and J.F. Lee. 2009. XANES evidence for sulphur speciation in Mn-, Ni-and W-bearing silicate melts. Geochim. Cosmochim. Acta 73: 6847-6867. Farhod Chasib, K. 2013. Extraction of phenolic pollutants (phenol and p-chlorophenol) from industrial wastewater. J. Chem. Eng. Data 58: 1549-1564. Filip, Z., K. Haider, H. Beutelspacher, and J.P. Martin. 1974. Comparisons of IR-spectra from melanins of microscopic soil fungi, humic acids and model phenol polymers. Geoderma 11: 37-52. Fukushima, M., K. Nakayasu, S. Tanaka, and H. Nakamura. 1995. Chromium(III) binding abilities of humic acids. Anal. Chim. Acta 317: 195-206. Görner, H. 2003. Photoprocesses of p-benzoquinones in aqueous solution. J. Phys. Chem. A 107: 11587-11595. Galgale, A.D., N.B. Shah, and N.G. Shah. 2014. Treatment of wastewater containing high concentration of phenol and total dissolved solids in moving bed biofilm reactor. Int. J. Inn. Res. Sci., Eng. Technol. 3: 10924-10930. Gan, D. 2005. Aqueous photochemistry of 1, 4-benzoquinones and their possible role in the photochemistry of natural organic matter. Ph.D. Dissertation. Department of Chemistry and Biochemistry, University of Maryland. Gonzalez-Vila, F.J., F. Martin, J.C. Delrio, and R. Fründ. 1992. Structural characteristics and geochemical significance of humic acids isolated from three Spanish lignite deposits. Sci. Total Environ. 118: 335-343. Greathouse, J.A., K.L. Johnson, and H.C. Greenwell. 2014. Interaction of natural organic matter with layered minerals: recent developments in computational methods at the nanoscale. Minerals 4: 519-540. Grevatt, P.C. 1988. Toxicological review of trivalent chromium. U.S. Environmental Protection Agency Washington, D.C., USA. Guibal, E., T. Vincent, E. Touraud, S. Colombo, and A. Ferguson. 2006. Oxidation of hydroquinone to p‐benzoquinone catalyzed by Cu (II) supported on chitosan flakes. J. Appl. Polym. Sci. 100: 3034-3043. Guo, W., J. Xu, J. Wang, Y. Wen, J. Zhuo, and Y. Yan. 2010. Characterization of dissolved organic matter in urban sewage using excitation emission matrix fluorescence spectroscopy and parallel factor analysis. J. Environ. Sci. 22: 1728-1734. Gupta, V.K., S. Agarwal, and T.A. Saleh. 2011. Chromium removal by combining the magnetic properties of iron oxide with adsorption properties of carbon nanotubes. Water Res. 45: 2207-2212. Hättenschwiler, S. and P.M. Vitousek. 2000. The role of polyphenols in terrestrial ecosystem nutrient cycling. Trends Ecol. Evol. 15: 238-243. Hardie, A.G., J.J. Dynes, L.M. Kozak, and P.M. Huang. 2007. Influence of Polyphenols on the Integrated Polyphenol-Maillard Reaction Humification Pathway as Catalyzed by Birnessite. Ann. Environ. Sci. 1: 91-110. Hardie, A.G., J.J. Dynes, L.M. Kozak, and P.M. Huang. 2009. The role of glucose in abiotic humification pathways as catalyzed by birnessite. J. Mol. Catal. A: Chem. 308: 114-126. Hays, M.D., P.M. Fine, C.D. Geron, M.J. Kleeman, and B.K. Gullett. 2005. Open burning of agricultural biomass: physical and chemical properties of particle-phase emissions. Atmos. Environ. 39: 6747-6764. Hedges, J.I. 1988. Polymerization of humic substances in natural environments. In humic substances and their role in the environment. John Wiley & Sons, New York, USA, pp. 45-58. Heymann, K., J. Lehmann, D. Solomon, M.W. Schmidt, and T. Regier. 2011. C 1s K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy for characterizing functional group chemistry of black carbon. Org. Geochem. 42: 1055-1064. Hotta, T.A. 2011. The Hydroquinone Debate. Plast. Surg. Nurs. 31: 115-116. Hseu, Z.-Y. and Y. Iizuka. 2013. Pedogeochemical characteristics of chromite in a paddy soil derived from serpentinites. Geoderma 202: 126-133. Hseu, Z.-Y., F. Zehetner, F. Ottner, and Y. Iizuka. 2015. Clay-mineral transformations and heavy-metal release in Paddy soils formed on serpentinites in eastern Taiwan. Clays Clay Miner. 63: 119-131. Hsu, L.C., Y.T. Liu, and Y.M. Tzou. 2015. Comparison of the spectroscopic speciation and chemical fractionation of chromium in contaminated paddy soils. J. Hazard. Mater. 296: 230-238. Hu, Y. and T.H. Boyer. 2017. Integrated bicarbonate-form ion exchange treatment and regeneration for DOC removal: Model development and pilot plant study. Water Res. 115: 40-49. Huang, S.W., P.N. Chiang, J.C. Liu, J.T. Hung, W.H. Kuan, Y.M. Tzou, S.L. Wang, J.H. Huang, C.C. Chen, and M.K. Wang. 2012. Chromate reduction on humic acid derived from a peat soil–Exploration of the activated sites on HAs for chromate removal. Chemosphere 87: 587-594. Huang, Y.Y., S.L. Wang, J.C. Liu, Y.M. Tzou, R.R. Chang, and J.H. Chen. 2008. Influences of preparative methods of humic acids on the sorption of 2, 4, 6-trichlorophenol. Chemosphere 70: 1218-1227. Hussain, A., S.K. Dubey, and V. Kumar. 2015. Kinetic study for aerobic treatment of phenolic wastewater. Water Resour. Ind. 11: 81-90. Ikan, R., Y. Rubinsztain, A. Nissenbaum, and I.R. Kaplan. 1996. The Maillard reaction: consequences for the chemical and life sciences. Wiley, Chichester, UK, pp. 1-25. James, B.R., J.C. Petura, R.J. Vitale, and G.R. Mussoline. 1995. Hexavalent chromium extraction from soils: a comparison of five methods. Environ. Sci. Technol. 29: 2377-2381. Jena, B.K. and C.R. Raj. 2008. Highly sensitive and selective electrochemical detection of sub-ppb level chromium(VI) using nano-sized gold particle. Talanta 76: 161-165. Jin, W., Z. Zhang, G. Wu, R. Tolba, and A. Chen. 2014. Integrated lignin-mediated adsorption-release process and electrochemical reduction for the removal of trace Cr(VI). RSC Adv. 4: 27843-27849. Jokic, A., A.I. Frenkel, and P.M. Huang. 2001a. Effect of light on birnessite catalysis of the Maillard reaction and its implication in humification. Can. J. Soil Sci. 81: 277-283. Jokic, A., A.I. Frenkel, M.A. Vairavamurthy, and P.M. Huang. 2001b. Birnessite catalysis of the Maillard reaction: Its significance in natural humification. Geophys. Res. Lett. 28: 3899-3902. Jokic, A., H.R. Schulten, J.N. Cutler, M. Schnitzer, and P.M. Huang. 2004a. A significant abiotic pathway for the formation of unknown nitrogen in nature. Geophys. Res. Lett. 31: L05502. Jokic, A., M.C. Wang, C. Liu, A.I. Frenkel, and P.M. Huang. 2004b. Integration of the polyphenol and Maillard reactions into a unified abiotic pathway for humification in nature: the role of δ-MnO2. Org. Geochem. 35: 747-762. Joschek, H.I. and S.I. Miller. 1966. Photooxidation of Phenol, Cresols, and Dihydroxybenzenes1, 2. J. Am. Chem. Soc. 88: 3273-3281. Kafilzadeh, F. and S. Saberifard. 2016. Isolation and identification of chromium(VI)-Resistant bacteria from Soltan Abad river sediments (Shiraz-Iran). Jundishapur J. Health Sci. 8: e33576. Kang, S. and B. Xing. 2005. Phenanthrene sorption to sequentially extracted soil humic acids and humins. Environ. Sci. Technol. 39: 134-140. Katsoyiannis, A. and C. Samara. 2007. The fate of dissolved organic carbon (DOC) in the wastewater treatment process and its importance in the removal of wastewater contaminants. Environ. Sci. Pollut. Res. 14: 284-292. Kelly, S.D., D. Hesterberg, and B. Ravel. 2008. Analysis of soils and minerals using X-ray absorption spectroscopy. Methods Soil Anal. 5: 387-463. Khachatryan, L., J. Adounkpe, Z. Maskos, and B. Dellinger. 2006. Formation of cyclopentadienyl radical from the gas-phase pyrolysis of hydroquinone, catechol, and phenol. Environ. Sci. Technol. 40: 5071-5076. Khodari, M., A.A. El-Rady, E. Rabee, and N. Nabil. 2014. Electro analytical determination of di hydroxybenzene isomers using glassy carbon electrode. J. Chem. Chem. Eng. 8: 654-661. Kim, H.-C. and M.-J. Yu. 2007. Characterization of aquatic humic substances to DBPs formation in advanced treatment processes for conventionally treated water. J. Hazard. Mater. 143: 486-493. Kim, J.I., G. Buckau, G.H. Li, H. Duschner, and N. Psarros. 1990. Characterization of humic and fulvic acids from Gorleben groundwater. Fresenius J. Anal. Chem. 338: 245-252. Kobya, M. 2004. Removal of Cr (VI) from aqueous solutions by adsorption onto hazelnut shell activated carbon: kinetic and equilibrium studies. Bioresour. Technol. 91: 317-321. Kulkarni, S.J. and J.P. Kaware. 2013. Review on research for removal of phenol from wastewater. Int. J. Sci. Res. Publ. 3: 1-5. Kumar, A.S.K., C.U. Kumar, V. Rajesh, and N. Rajesh. 2014. Microwave assisted preparation of n-butylacrylate grafted chitosan and its application for Cr(VI) adsorption. Int. J. Biol. Macromol. 66: 135-143. Kurien, K.C. and P.A. Robins. 1970. Photolysis of aqueous solutions of p-benzoquinone: a spectrophotometric investigation. J. Chem. Soc. B: Phys. Org.: 855-859. Lan, Y.Q., J.X. Yang, and B. Deng. 2006. Catalysis of dissolved and adsorbed iron in soil suspension for chromium(VI) reduction by sulfide. Pedosphere 16: 572-578. Legros, S., P. Chaurand, J. Rose, A. Masion, V. Briois, J.H. Ferrasse, H.S. Macary, J.Y. Bottero, and E. Doelsch. 2010. Investigation of copper speciation in pig slurry by a multitechnique approach. Environ. Sci. Technol. 44: 6926-6932. Levitt, J. 2007. The safety of hydroquinone: a dermatologist's response to the 2006 Federal Register. J. Am. Acad. Dermatol. 57: 854-872. Li, C., Y.Q. Lan, and B.L. Deng. 2007. Catalysis of manganese(II) on chromium(VI) reduction by citrate. Pedosphere 17: 318-323. Li, L., W. Huang, P.a. Peng, G. Sheng, and J. Fu. 2003. Chemical and molecular heterogeneity of humic acids repetitively extracted from a peat. Soil Sci. Soc. Am. J. 67: 740-746. Liang, B., J. Lehmann, D. Solomon, S. Sohi, J.E. Thies, J.O. Skjemstad, F.J. Luizao, M.H. Engelhard, E.G. Neves, and S. Wirick. 2008. Stability of biomass-derived black carbon in soils. Geochim. Cosmochim. Acta 72: 6069-6078. Liu, C. and P.M. Huang. 2002. Role of hydroxy-aluminosilicate ions (proto-imogolite sol) in the formation of humic substances. Org. Geochem. 33: 295-305. Liu, M.M., X.H. Cao, W.F. Tan, X.H. Feng, G.H. Qiu, X.H. Chen, and F. Liu. 2011. Structural controls on the catalytic polymerization of hydroquinone by birnessites. Clay Clay Miner. 59: 525-537. Lu, X.Q., J.V. Hanna, and W.D. Johnson. 2000. Source indicators of humic substances: an elemental composition, solid state 13C CP/MAS NMR and Py-GC/MS study. Appl. Geochem. 15: 1019-1033. Lugo-Lugo, V., L.A. Bernal-Martínez, F. Ureña-Núñez, I. Linares-Hernández, P.T. Almazán-Sánchez, and P. de JB Vázquez-Santillán. 2014. Treatment of Cr (VI) present in plating wastewater using a Cu/Fe galvanic reactor. Fuel 138: 203-214. Ma, H., Y. Xu, Z. Rong, X. Cheng, S. Gao, X. Zhang, H. Zhao, and L. Huo. 2012. Highly toluene sensing performance based on monodispersed Cr2O3 porous microspheres. Sens. Actuators B: Chem. 174: 325-331. Maillard, L.C. 1913. Formation de matieres humiques par action de polypeptides sur sucres. CR Acad. Sci 156: 148-149. Majcher, E.H., J. Chorover, J.M. Bollag, and P.M. Huang. 2000. Evolution of CO during Birnessite-Induced Oxidation of C-Labeled Catechol. Soil Sci. Soc. Am. J. 64: 157-163. Mao, J.D., W.G. Hu, K. Schmidt-Rohr, G. Davies, E.A. Ghabbour, and B. Xing. 2000. Quantitative characterization of humic substances by solid-state carbon-13 nuclear magnetic resonance. Soil Sci. Soc. Am. J. 64: 873-884. Marinho, B.A., R.O. Cristóvão, J.M. Loureiro, R.A. Boaventura, and V.J. Vilar. 2016. Solar photocatalytic reduction of Cr(VI) over Fe(III) in the presence of organic sacrificial agents. Appl. Catal. B: Environ. 192: 208-219. Marquardt, R., S. Grandjean, and R. Bonneau. 1992. Competition between intersystem crossing and intramolecular electron transfer in substituted benzoquinones. J. Photochem. Photobiol. A: Chem. 69: 143-153. Maurya, M.R. and S. Sikarwar. 2007. Oxidation of phenol and hydroquinone catalysed by copper(II) and oxovanadium(IV) complexes of N, N'-bis(salicyledene) diethylenetriamine (H2 saldien) covalently bonded to chloromethylated polystyrene. J. Mol. Catal. A: Chem. 263: 175-185. McElvenny, D.M., A.J. Darnton, J.T. Hodgson, S.D. Clarke, R.C. Elliott, and J. Osman. 2003. Investigation of cancer incidence and mortality at a Scottish semiconductor manufacturing facility. Occup. Med. 53: 419-430. Mebrahtu, G. and S. Zerabruk. 2011. Concentration and health implication of heavy metals in drinking water from urban areas of Tigray region, Northern Ethiopia. Momona Ethiopian J. Sci. 3: 105-121. Meyrowitz, S. 2007. Nutritional supplement. In Nutritional supplement: Google Patents. Moafi, H.F., R. Ansari, and F. Ostovar. 2016. Ag2O/Sawdust nanocomposite as an efficient adsorbent for removal of hexavalent chromium ions from aqueous solutions. J. Mater. Environ. Sci. 7: 2051-2068. Mukhopadhyay, B., J. Sundquist, and R.J. Schmitz. 2007. Removal of Cr(VI) from Cr-contaminated groundwater through electrochemical addition of Fe(II). J. Environ. Manage. 82: 66-76. Nakayama, E., T. Kuwamoto, S. Tsurubo, H. Tokoro, and T. Fujinaga. 1981. Chemical speciation of chromium in sea water: Part 1. Effect of Naturally Occurring Organic Materials on the Complex Formation of Chromium(III). Anal. Chim. Acta 130: 289-294. Namasivayam, C. and M. Sureshkumar. 2008. Removal of chromium(VI) from water and wastewater using surfactant modified coconut coir pith as a biosorbent. Bioresour. Technol. 99: 2218-2225. Newville, M. 2001. IFEFFIT: interactive XAFS analysis and FEFF fitting. J. Synchrot. Radiat. 8: 322-324. Nieboer, E. and W.E. Sanford. 1985. Essential, Toxic and Therapeutic Functions of Metals (Including Determinants of Reactivity). Rev. Biochem. Toxicol. 7: 205-245. Oh, Y.J., H. Song, W.S. Shin, S.J. Choi, and Y.H. Kim. 2007. Effect of amorphous silica and silica sand on removal of chromium(VI) by zero-valent iron. Chemosphere 66: 858-865. Ohta, A., H. Kagi, H. Tsuno, M. Nomura, and T. Okai. 2012. Speciation study of Cr(VI/III) reacting with humic substances and determination of local structure of Cr binding humic substances using XAFS spectroscopy. Geochem. J. 46: 409-420. Ohta, A., H. Kagi, H. Tsuno, M. Nomura, T. Okai, and N. Yanagisawa. 2011. IR and XANES spectroscopic studies of humic acids reacting with Cr(III) and Cr(VI). Bull Geol Surv Jpn 62: 347-355. Ononye, A.I., A.R. McIntosh, and J.R. Bolton. 1986. Mechanism of the photochemistry of p-benzoquinone in aqueous solutions. 1. Spin trapping and flash photolysis electron paramagnetic resonance studies. J. Phys. Chem. 90: 6266-6270. Owalude, S.O. and A.C. Tella. 2016. Removal of hexavalent chromium from aqueous solutions by adsorption on modified groundnut hull. J. Basic Appl. Sci. 5: 377-388. Owlad, M., M.K. Aroua, W.A.W. Daud, and S. Baroutian. 2009. Removal of hexavalent chromium-contaminated water and wastewater: a review. Water Air Soil Pollut. 200: 59-77. Oze, C., S. Fendorf, D.K. Bird, and R.G. Coleman. 2004. Chromium geochemistry of serpentine soils. Int. Geol. Rev. 46: 97-126. Park, D., Y.-S. Yun, J.H. Jo, and J.M. Park. 2005. Mechanism of hexavalent chromium removal by dead fungal biomass of Aspergillus niger. Water Res. 39: 533-540. Park, D., Y.S. Yun, and J.M. Park. 2008. XAS and XPS studies on chromium-binding groups of biomaterial during Cr(VI) biosorption. J. Colloid Interface Sci. 317: 54-61. Pertusatti, J. and A.G. Prado. 2007. Buffer capacity of humic acid: Thermodynamic approach. J. Colloid Interface Sci. 314: 484-489. Pettit, R.E. 2004. Organic matter, humus, humate, humic acid, fulvic acid and humin: Their importance in soil fertility and plant health. Texas A&M University, Texas, USA. Rai, D., B.M. Sass, and D.A. Moore. 1987. Chromium(III) hydrolysis constants and solubility of chromium(III) hydroxide. lnorg. Chem. 26: 345-349. Rai, D. and J.M. Zachara. 1986. Geochemical behavior of chromium species. In Geochemical behavior of chromium species. Pacific Northwest Lab., Richland, Washington, USA. Ravel, B. and M. Newville. 2005. ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. J. Synchrot. Radiat. 12: 537-541. Remoundaki, E., A. Hatzikioseyian, and M. Tsezos. 2007. A systematic study of chromium solubility in the presence of organic matter: consequences for the treatment of chromium‐containing wastewater. J. Chem. Technol. Biotechnol. 82: 802-808. Rengaraj, S., K.H. Yeon, and S.H. Moon. 2001. Removal of chromium from water and wastewater by ion exchange resins. J. Hazard. Mater. 87: 273-287. Richard, F.C. and A.C.M. Bourg. 1991. Aqueous geochemistry of chromium: a review. Water Res. 25: 807-816. Risser, J.A. and G.W. Bailey. 1992. Spectroscopic study of surface redox reactions with manganese oxides. Soil Sci. Soc. Am. J. 56: 82-88. Rodríguez, I.N., J.A.M. Leyva, and J.L.H.H. de Cisneros. 1997. Use of a bentonite-modified carbon paste electrode for the determination of some phenols in a flow system by differential-pulse voltammetry. Analyst 122: 601-604. Rosales-Landeros, C., C.E. Barrera-Díaz, B. Bilyeu, V.V. Guerrero, and F.U. Núñez. 2013. A review on Cr(VI) adsorption using inorganic materials. Am. J. Anal. Chem. 4: 8-16. Sabaa, M.W., T.M. Madkour, and A.A. Yassin. 1988. Polymerization products of p-Benzoquinone as bound antioxidants for styrene-butadiene rubber: Part I-Preparation of quinone polymers. Polym. Degrad. Stab. 22: 195-203. Saha, R., R. Nandi, and B. Saha. 2011. Sources and toxicity of hexavalent chromium. J. Coord. Chem. 64: 1782-1806. Saiz-Jimenez, C., K. Haider, and J. Martin. 1975. Anthraquinones and phenols as intermediates in the formation of dark-colored, humic acid-like pigments by Eurotium echinulatum. Soil Sci. Soc. Am. J. 39: 649-653. Saleh, F.Y., G.E. Mbamalu, Q.H. Jaradat, and C.E. Brungardt. 1996. Ion chromatography-photodiode array UV-visible detection of Cr(III) hydrolytic polymerization products in pure and natural waters. Anal. Chem. 68: 740-745. Salnikow, K. and A. Zhitkovich. 2007. Genetic and epigenetic mechanisms in metal carcinogenesis and cocarcinogenesis: nickel, arsenic, and chromium. Chem. Res. Toxicol. 21: 28-44. Sanchez-Cortes, S., O. Francioso, J.V. Garcıa-Ramos, C. Ciavatta, and C. Gessa. 2001. Catechol polymerization in the presence of silver surface. Colloids Surf. Physicochem. Eng. Aspects 176: 177-184. Santos, A., P. Yustos, A. Quintanilla, F. Garcia-Ochoa, J. Casas, and J. Rodriguez. 2004. Evolution of toxicity upon wet catalytic oxidation of phenol. Environ. Sci. Technol. 38: 133-138. Santos, A., P. Yustos, A. Quintanilla, S. Rodrıguez, and F. Garcıa-Ochoa. 2002. Route of the catalytic oxidation of phenol in aqueous phase. Appl. Catal. B: Environ. 39: 97-113. Schnitzer, M. 1999. A lifetime perspective on the chemistry of soil organic matter. Adv. Agron. 68: 1-58. Schnitzer, M. and P. Schuppli. 1989. Method for the sequential extraction of organic matter from soils and soil fractions. Soil Sci. Soc. Am. J. 53: 1418-1424. Schuchmann, M., J. Sonntag, and C. Sonntag. 1998. Reaction of OH radicals with benzoquinone in aqueous solutions. A pulse radiolysis study. J. Chem. Soc., Perkin Transactions 2: 791-796. Shen, Y.S., S.L. Wang, Y.M. Tzou, Y.Y. Yan, and W.H. Kuan. 2012. Removal of hexavalent Cr by coconut coir and derived chars-The effect of surface functionality. Bioresour. Technol. 104: 165-172. Sherine, B., A.A. Nasser, and S. Rajendran. 2010. Inhibitive action of hydroquinone-Zn2+ system in controlling the corrosion of carbon steel in well water. International Journal of Engineering Science and Technology 2: 341-357. Shi, X. 1999. Reduction of chromium(VI) and its relationship to carcinogenesis. J. Toxicol. Environ. Health, Part B: Crit. Rev. 2: 87-104. Shindo, H. and P.M. Huang. 1984a. Catalytic effects of manganese(IV), iron(III), aluminum, and silicon oxides on the formation of phenolic polymers. Soil Sci. Soc. Am. J. 48: 927-934. Shindo, H. and P.M. Huang. 1992. Comparison of the influence of Mn(IV) oxide and tyrosinase on the formation of humic substances in the environment. Sci. Total Environ. 117: 103-110. Shindo, H. and P.M. Huang. 1982. Role of Mn(IV) oxide in abiotic formation of humic substances in the environment. Nature 298: 363-365. Shindo, H. and P.M. Huang. 1984b. Significance of Mn(IV) oxide in abiotic formation of organic nitrogen complexes in natural environments. Nature 308: 57-58. Shirai, M., T. Awatsuji, and M. Tanaka. 1975. Photolysis of p-benzoquinone in aqueous solution. Possibility of a polar mechanism in the primary process. Bull. Chem. Soc. Jpn. 48: 1329-1330. Shirzad, S.M., M.R. Samarghandi, S. Azizian, W.G. Kim, and S.M. Lee. 2011. The removal of hexavalent chromium from aqueous solutions using modified holly sawdust: equilibrium and kinetics studies. Environ. Eng. Res. 16: 55-60. Singh, B., Y. Fang, B.C. Cowie, and L. Thomsen. 2014. NEXAFS and XPS characterisation of carbon functional groups of fresh and aged biochars. Org. Geochem. 77: 1-10. Singh, V., A.K. Sharma, P. Kumari, and S. Tiwari. 2008. Efficient chromium (VI) adsorption by Cassia marginata seed gum functionalized with poly (methylmethacrylate) using microwave irradiation. Ind. Eng. Chem. Res. 47: 5267-5276. Sposito, G. 2008. The chemistry of soils. Oxford university press, New York, USA. Steelink, C. 1985. Implications of elemental characteristics of humic substances: In Humic substances in soil, sediment, and water. John Wiley & Sons, New York, USA. Stevenson, F.J. 1994. Humus chemistry: genesis, composition, reactions. John Wiley & Sons, New York, USA. Stevenson, I.L. and M. Schnitzer. 1982. TRANSMISSION ELECTRON MICROSCOPY OF EXTRACTED FULVIC AND HUMIC ACIDS1. Soil Sci. 133: 179-185. Stoppler, M.C. and J.W. Marks. 2010. FDA proposes hydroquinone ban: A Journal of Culture and African Women Studies. Africa Resource Centre, Nairobi, Kenya. Suksabye, P., P. Thiravetyan, W. Nakbanpote, and S. Chayabutra. 2007. Chromium removal from electroplating wastewater by coir pith. J. Hazard. Mater. 141: 637-644. Sun, J., J.D. Mao, H. Gong, and Y.Q. Lan. 2009. Fe(III) photocatalytic reduction of Cr(VI) by low-molecular-weight organic acids with α-OH. J. Hazard. Mater. 168: 1569-1574. Sun, Y.G., H. Cui, Y.H. Li, and X.Q. Lin. 2000. Determination of some catechol derivatives by a flow injection electrochemiluminescent inhibition method. Talanta 53: 661-666. Suresh, S., V.C. Srivastava, and I.M. Mishra. 2012. Adsorption of catechol, resorcinol, hydroquinone, and their derivatives: a review. Int. J. Energy Environ. Eng. 3: 1-19. Sze, C.C., C.Y. Shi, and C.N. Ong. 1996. Cytotoxicity and DNA strand breaks induced by benzene and its metabolites in Chinese hamster ovary cells. J. Appl. Toxicol. 16: 259-264. Takenaka, S., J. Koshiya, S. Okugawa, A. Takata, S. Murakami, and K. Aoki. 2011. Fe-superoxide dismutase and 2-hydroxy-1, 4-benzoquinone reductase preclude the auto-oxidation step in 4-aminophenol metabolism by Burkholderia sp. strain AK-5. Biodegradation 22: 1-11. Talhout, R., T. Schulz, E. Florek, J. Van Benthem, P. Wester, and A. Opperhuizen. 2011. Hazardous compounds in tobacco smoke. Int. J. Environ. Res. Public Health 8: 613-628. Tan, K.H. 2014. Humic matter in soil and the environment: principles and controversies. CRC Press, Boca Raton, USA, pp. 58-60. Tang, Y., E.J. Elzinga, Y.J. Lee, and R.J. Reeder. 2007. Coprecipitation of chromate with calcite: batch experiments and X-ray absorption spectroscopy. Geochim. Cosmochim. Acta 71: 1480-1493. Tate III, R.L. 1987. Soil organic matter: Biological and ecological effects. John Wiley and Sons, New York, USA, pp. 1-25, 114-164. Tian, X.F., X.C. Gao, F. Yang, Y.Q. Lan, J.D. Mao, and L.X. Zhou. 2010. Catalytic role of soils in the transformation of Cr(VI) to Cr(III) in the presence of organic acids containing α-OH groups. Geoderma 159: 270-275. Torkmahalleh, M.A., L. Lin, T.M. Holsen, D.H. Rasmussen, and P.K. Hopke. 2012. The impact of deliquescence and pH on Cr speciation in ambient PM samples. Aerosol Sci. Technol. 46: 690-696. Tzou, Y.M., M.K. Wang, and R.H. Loeppert. 2004. Organic ligand-enhanced photochemical reduction and immobilization of chromium(VI) on TiO2 particles in acidic aqueous media. Soil Sci. 169: 413-422. Uchimiya, M. and A.T. Stone. 2006. Redox reactions between iron and quinones: thermodynamic constraints. Geochim. Cosmochim. Acta 70: 1388-1401. USEPA. 1993. Integrated Risk Information System (IRIS) on Chromium(III). Office of Research and Development, National Center for Environmental Assessment, Washington, D.C., USA. Uyguner, C.S., C. Hellriegel, W. Otto, and C.K. Larive. 2004. Characterization of humic substances: Implications for trihalomethane formation. Anal. Bioanal. Chem. 378: 1579-1586. Venkateswaran, P. and K. Palanivelu. 2005. Studies on recovery of hexavalent chromium from plating wastewater by supported liquid membrane using tri-n-butyl phosphate as carrier. Hydrometallurgy 78: 107-115. von Sonntag, J., E. Mvula, K. Hildenbrand, and C. von Sonntag. 2004. Photohydroxylation of 1, 4‐Benzoquinone in Aqueous Solution Revisited. Chem.-Eur. J. 10: 440-451. Waksman, S.A. 1932. CONTRIBUTION TO OUR KNOWLEDGE OF THE CHEMICAL NATURE AND ORIGIN OF HUMUS: I. ON THE SYNTHESIS OF THE' HUMUS NUCLEUS'. Soil Sci. 34: 43-70. Wang, M.C. and P.M. Huang. 2003. Cleavage and polycondensation of pyrogallol and glycine catalyzed by natural soil clays. Geoderma 112: 31-50. Wang, M.C. and P.M. Huang. 1986. Humic macromolecule interlayering in nontronite through interaction with phenol monomers. Nature 323: 529-531. Wang, M.C. and P.M. Huang. 2000. Ring cleavage and oxidative transformation of pyrogallol catalyzed by Mn, Fe, Al, and Si oxides. Soil Sci. 165: 934-942. Wang, S.L. and J.F. Lee. 2011. Reaction mechanism of hexavalent chromium with cellulose. Chem. Eng. J. 174: 289-295. Weckhuysen, B.M. and I.E. Wachs. 1996. Raman spectroscopy of supported chromium oxide catalysts. Determination of chromium-oxygen bond distances and bond orders. J. Chem. Soc., Faraday Trans. 92: 1969-1973. Wilson, A.D. and J.W. Nicholson. 2005. Acid-base cements: their biomedical and industrial applications. Cambridge University Press, Cambridge, UK, pp. 100-205. Wu, S., H. Shi, H. Wu, S. Yan, J. Guo, Y. Sun, and L. Pan. 2012. Treatment of melasma with oral administration of tranexamic acid. Aesthetic Plast. Surg. 36: 964-970. Wu, Z. and M. Zhou. 2001. Partial degradation of phenol by advanced electrochemical oxidation process. Environ. Sci. Technol. 35: 2698-2703. Xu, X.R., H.B. Li, X.Y. Li, and J.D. Gu. 2004. Reduction of hexavalent chromium by ascorbic acid in aqueous solutions. Chemosphere 57: 609-613. Yamamoto, T. 2008. Assignment of pre‐edge peaks in K‐edge x‐ray absorption spectra of 3d transition metal compounds: electric dipole or quadrupole? X‐Ray Spectrom. 37: 572-584. Yang, C., Y. Jiang, L. Zhang, and Y. Qian. 2006. Liquid− liquid equilibria for the ternary system methyl isobutyl ketone+ water+ hydroquinone. J. Chem. Eng. Data 51: 2107-2109. Yang, H., R. Yan, H. Chen, D.H. Lee, and C. Zheng. 2007. Characteristics of hemicellulose, cellulose and lignin pyrolysis. Fuel 86: 1781-1788. Yang, J.W., Z.S. Tang, R.F. Guo, and S.Q. Chen. 2008. Soil surface catalysis of Cr(VI) reduction by citric acid. Environ. Prog. 27: 302-307. Young, C.C., P.D. Rekha, and A.B. Arun. 2005. What Happens During Composting? Food and Fertilizer technology Centre (FFTC) for The Asian and Pacific Region. FFTC Publication Database, Taipei, Taiwan, pp. 01-12. Zapico, R.R., P. Marín, F.V. Díez, and S. Ordóñez. 2015. Influence of operation conditions on the copper-catalysed homogeneous wet oxidation of phenol: Development of a kinetic model. Chem. Eng. J. 270: 122-132. Zargar, B. and A. Hatamie. 2012. Colorimetric determination of resorcinol based on localized surface plasmon resonance of silver nanoparticles. Analyst 137: 5334-5338. Zhao, D., A.K. SenGupta, and L. Stewart. 1998. Selective removal of Cr(VI) oxyanions with a new anion exchanger. Ind. Eng. Chem. Res. 37: 4383-4387. Zhao, G., M. Li, Z. Hu, H. Li, and T. Cao. 2006. Electrocatalytic redox of hydroquinone by two forms of L-proline. J. Mol. Catal. A: Chem. 255: 86-91. Zhitkovich, A. 2011. Chromium in drinking water: sources, metabolism, and cancer risks. Chem. Res. Toxicol. 24: 1617-1629. Zhitkovich, A. 2005. Importance of chromium-DNA adducts in mutagenicity and toxicity of chromium(VI). Chem. Res. Toxicol. 18: 3-11.
摘要: 對苯二酚與重金屬鉻皆被廣泛地應用在半導體製造、皮革製造、顯影、油漆等化學工業上,是工業廢水中常見的污染物。此外,在降解受苯酚汙染的廢水處理過程中,苯酚也會轉變成有毒性且不易降解的對苯二酚和醌類等的中間產物。六價鉻具有高毒性、致癌性以及會對生物造成突變性,因此,將廢水中的六價鉻還原成三價鉻以降低六價鉻在自然界中的毒性和移動性為最主要減低鉻危害的策略。六價鉻為一強氧化劑,當其與水溶液中之有機物/膠體反應時,可將有機物氧化,且此反應可因光的介入而增強。然而,反應中有機物亦可能因部分分解造成可溶性有機碳(DOC)的增加和/或生成有毒性的中間產物,影響後續廢水處理的成效。根據前人研究指出,錳氧化物能促進有機分子(如對苯二酚)氧化聚合生成類腐植物質,故當六價鉻與酚類化合物反應時,有機化合物被六價鉻氧化成DOC或二氧化碳可能並非唯一的反應途徑,因此,本研究的目的為探討在酸性條件下,六價鉻與多酚化合物,即對苯二酚,的氧化還原反應,以及在施予光照 (100瓦中壓汞燈,最大輻射強度於波長366 nm) 時對所生成反應產物之影響,同時,反應所形成的氧化聚合產物之結構將以光譜分析,並與天然的腐植酸以及在高pH值下由多酚類/醌類所合成的聚合物相互比較。此外,過氧化氫亦為一氧化劑,在本研究中,其將被用來取代六價鉻來氧化對苯二酚,以評估三價鉻金屬離子在氧化聚合過程中所扮演的角色。結果顯示,當67.3 µM六價鉻與181.6 µM對苯二酚反應時,對苯醌為唯一的有機產物;而在光系統下,則有產物1,2,4-苯三酚和2-羥基-對苯醌的生成。隨著對苯二酚和六價鉻濃度的增加,有機分子會發生氧化聚合反應並生成含三價鉻的有機聚合物,且研究發現,對苯醌可能為促使後續氧化聚合的重要中間產物。根據X光吸收近邊緣結構的線性疊加擬合分析結果,此有機聚合物主要有78.0-90.4%是以三價鉻鍵結至較大的有機物聚合物的型態存在,顯示六價鉻不僅會氧化對苯二酚,也能進一步藉由生成的三價鉻將部分分解的中間產物聚合,生成含有三價鉻鍵結的類腐植物質。不同於天然腐植酸有脂肪族碳和芳香族碳的結構,該有機聚合物是以芳香族碳結構為主。當提高溶液pH值至10.0時,對苯二酚或對苯醌亦會發生聚合反應,而不同於六價鉻系統,其聚合物有較明顯的羧酸(COOH)結構。對苯二酚與對苯醌在高pH下的聚合產物其化學結構仍以芳香族碳的結構為主,但對苯醌系統存在有較明顯的脂肪族結構。另一方面,不論光照與否,在沒有金屬離子的存在下,即過氧化氫系統,則無法有效地促進對苯二酚的聚合反應,而生成的對苯醌會再轉變成2-羥基-對苯醌和其它有機酸。故在酸性條件下,六價鉻能促進對苯二酚的氧化聚合反應。然而,相較於對苯二酚及對苯醌在高pH下的系統,則金屬扮演著連接聚合之芳香性有機分子的一個重要之角色。
Hydroquinone (H2Q) and chromium (Cr) are widely used in semiconductor manufacturing processes, tanning, photography, paint, etc., and they are the major environmental pollutants in industrial wastewaters. It was also found that the formation of toxic and less degradable intermediate products, such as H2Q and quinones, at early stages of phenol degradation in phenol-containing wastewaters. Chromium(VI) is a toxic and carcinogenic element, and it will cause mutagenic effects to organisms. Therefore, reduction of Cr(VI) to Cr(III) in the wastewater is an important strategy for eliminating the toxicity and mobility of Cr(VI) in nature. Chromium(VI) is a strong oxidant, and upon its interaction with organic matter/colloids in solutions, the organic compounds can be mineralized and the reaction is enhanced under illumination. However, an increase in dissolved organic carbon (DOC) and/or the formation of toxic intermediate products may occur if the organic materials are partially decomposed which may affect the efficiency of wastewater treatment systems. It is well-known that manganese (Mn) oxides can promote the oxidative polymerization of H2Q to humic-like polymers. Based on the findings, we hypothesized that the oxidative decompositions of organic compounds, forming DOC or CO2, may not be the only pathway of the redox reaction involving Cr(VI) and phenolic compounds. Thus, this study aims to investigate the redox reactions of Cr(VI) and H2Q, a model organic compound of the polyphenols, in an acidic condition, and their reactive products as influenced by ultraviolet (UV) irradiation (a medium-pressure mercury lamp with the maximum intensity of illumination at 366 nm). The structures of oxidative polymerization products are spectroscopically analyzed and compared to the natural humic acids and the reactive products of polyphenols/quinones at a high pH value. In addition, the hydrogen peroxide (H2O2), a substitute oxidant of Cr(VI), will be used to oxidize H2Q for evaluating the roles of metal ions of Cr(III) in the oxidative polymerization process. The results showed that when 67.3 µM Cr(VI) reacted with 181.6 µM H2Q, 1,4-benzoquinone (BQ) was the only organic product, but 1,2,4-benzenetriol (Ph(OH)3) and 2-hydroxy-1,4-benzoquinone (BQ(OH)) were produced when UV irradiation was provided. With an increase in the H2Q and Cr(VI) concentrations, the oxidative polymerization of organic molecules occurred, and the derived organic polymers contained Cr(III). The BQ was probably the primary intermediate of H2Q that induced the subsequent oxidative polymerization reaction in the presence of Cr(VI). The linear combination fitting of the XANES spectra demonstrated that the organic polymers consisted of 78.0-90.4% Cr(III)-humic-like polymers, suggesting that Cr(III) may act as a linkage of organic molecules during the polymerization processes of H2Q. This study indicates that polymerization of oxidized organic molecules occurs even in the presence of a strong oxidant of Cr(VI). The aromatic domains dominated the chemical structures of the organic polymers, different from natural humic acids with both aliphatic and aromatic carbons. The polymerization of H2Q or BQ also occurred when the solution pH value was adjusted to 10.0. Unlike the products of Cr(VI)/H2Q, the polymerized products of H2Q/BQ bore mainly the aromatic domains with more characteristic peaks of COOH exhibited in the polymers. It was found that the obviously aliphatic structures existed in the BQ system. The H2O2 could not promote the polymerization of H2Q either in the presence or absence of UV irradiation. Because the BQ, the important precursor of organic polymer, would be converted to BQ(OH) and other organic acids upon its formation in the presence of H2O2, we presumed this associated with the lack of binding metals may lead to a change in the reactive pathways of H2Q. In summary, the oxidative polymerization of H2Q could be promoted by Cr(VI) in an acidic solution; however, metals played an important role of linkage of these aromatic enriched polymers as compared to the reactive products of H2Q and BQ at a high pH.
URI: http://hdl.handle.net/11455/96249
文章公開時間: 10000-01-01
Appears in Collections:土壤環境科學系

文件中的檔案:

取得全文請前往華藝線上圖書館



Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.