There are currently two major environmentally significant projects in the Margerum lab. Both the Water Treatment Project and the Arctic Project involve aqueous non-metal redox kinetics. Water chlorination, the most common source of water treatment, and water bromination are two effective means of disinfecting wastewater. The amount of halogen necessary to accomplish disinfection is described by breakpoint halogenation. If too little halogen is used, then complete disinfection does not occur. If too much halogen is used, then various side products (hazardous and non-hazardous) form. Characterization of these processes are, therefore, very important. We have been studying reactions in the Margerum lab that help characterize water treatment processes for the past 25 years.
Efforts in this area have included the kinetics and/or mechanisms of:
the formation and equilibria of chloramines (119,120);
the reactions of hypohalites and hypohalous acids with cyanide (195,205);
reactions of the chloramines with sulfite (193),
ammonia (194), bromine, tribromide, hypobromous
acid, and hypobromite (203,207),
nitrite ion (208), cyanide ion (214),
bromide (215), and formaldehyde (228);
formation of bromochloramines (203,207);
the hydrolysis of bromine and chlorine (209,217);
the oxidation of hydroxylamine by aqueous chlorine or bromine (206,211);
the equilibrium of bromine monochloride in solutions of high bromide or
high chloride (212); the disproportionation
of hypobromous acid (222); chlorine dioxide
and chlorate formation by hypobromous acid/chlorite ion reaction (224);
BrCl kinetics and equilibria (226, 231,236);
the reactions of ozone with various reducing agents (232,
237); and the decomposition of HOCl/HOBr reaction
mixtures (235).
The other environmentally significant project studied in our lab is the Arctic Project. It is a collaborative effort with Paul Shepson (Chemistry / Earth and Atmospheric Sciences), Joe Francisco (Chemistry / EAS), and Wen-Yih Sun (EAS) in which we are searching for an explanation to ozone depletion in the Arctic troposphere during the polar sunrise. The focus of contribution from the Margerum lab involves solution phase kinetics of bromine monochloride, bromine, hypobromous acid, ozone, and sulfer(IV) reactions under Arctic temperatures and conditions. Robert Becker is currently working on this project, with work initiated in this lab by Qian Liu and Wenzel Bartlett. Work completed includes the temperature dependence of BrCl hydrolysis (236), reverse bromine hydrolysis (236), and Br2(Br3-)/S(IV) (236) reactions, the temperature dependence of the BrCl/BrCl2- equilibrium (231), and the Henry's law constant and hydrolysis equilibrium constant of BrCl (226). All the above studies are significant in creating a better model of Arctic ozone depletion during polar sunrise.
Last updated 25 May 2002, Kara Huff Hartz and Robert Becker
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