Kinetics and mechanisms of the reactions of monochloramine with nitrite ion, chloramines with cyanide ion, and ozone with inorganic nucleophiles

Lynn Marie Schurter, Purdue University

Abstract

Since monochloramine can oxidize nitrite (both commonly present in wastewater treatment systems) to nitrate ion, it is important to understand this reaction as it is a source of chlorine demand. Spectrophotometric techniques were used to collect kinetic data on this reaction under pseudo first-order reaction conditions with nitrite in excess. It was determined that this reaction proceeds via a Cl$\sp{+}$-transfer mechanism analogous to that of the reaction of hypochlorous acid with nitrite ion. Cyanogen chloride is an undersirable byproduct in chloraminated wastewater treatment systems. Proposed mechanisms for the formation of cyanogen chloride include the reaction of chloramine with nitriles and other organic nitrogen-containing compounds. Thus, the reactions of the simplest nitrile, cyanide ion with mono-, di-, and trichloramine were studied. The kinetics of the reactions proved that they proceed via Cl$\sp{+}$-transfer mechanisms, to form cyanogen chloride, with only the monochloramine reaction exhibiting general-acid assistance. Ozone is also used for wastewater treatment and occurs naturally in the atmosphere. It is important to understand the reactions of ozone with inorganic nucleophiles to be able to model these reactions in real world systems (i.e. wastewater treatment or environmental systems). Stopped-flow and pulsed-accelerated flow spectrophotometric methods were used to monitor ozone loss with time in the study of the ozone reactions. All of the reactions of ozone with nitrite, iodide, sulfite and bromide ions are first-order in ozone and nucleophile concentrations and appear to proceed via oxygen-atom transfer mechanisms. Attempts to obtain reliable data for the reaction of ozone with cyanide ion under a wide range of reaction conditions were made, but reproducible data for this reaction were not obtained.

Degree

Ph.D.

Advisors

Margerum, Purdue University.

Subject Area

Chemical engineering|Inorganic chemistry|Civil engineering

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