Tertiary amine-catalyzed generation of chlorine dioxide from hypochlorous acid and chlorite ions
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Tertiary amine‑catalyzed generation of chlorine dioxide from hypochlorous acid and chlorite ions Estefania Isaza Ferro1 · Jordan Perrin1 · Owain George John Dawson1 · Tapani Vuorinen1 Received: 18 February 2020 / Accepted: 10 November 2020 © The Author(s) 2020
Abstract The reaction between hypochlorous acid and chlorite ions is the rate limiting step for in situ chlorine dioxide regeneration. The possibility of increasing the speed of this reaction was analyzed by the addition of tertiary amine catalysts in the system at pH 5. Two amines were tested, DABCO (1,4-diazabicyclo[2.2.2]octane) and its derivative CEM-DABCO (1-carboethoxymethyl-1-azonia-4-aza-bicyclo[2.2.2]octane chloride). The stability of the catalysts in the presence of both reagents and chlorine dioxide was measured, with CEM-DABCO showing to be highly stable with the mentioned chlorine species, whereas DABCO was rapidly degraded by chlorine dioxide. Hence, CEM-DABCO was chosen as a suitable candidate to catalyze the reaction of hypochlorous acid with chlorite ions and it significantly increased the speed of this reaction even at low catalyst dosages. This research opens the door to a faster regeneration of chlorine dioxide and an improved efficiency in chlorine dioxide treatments.
Introduction Tertiary amines are versatile compounds that can catalyze a wide range of organic (Ammer et al. 2010) and oxidation reactions (Prütz 1998; Huang and Shah 2018). They are versatile catalysts because of their nucleophilic character and their availability to incorporate different functional groups, which may provide higher stability and reactivity (Prütz 1998; Shah et al. 2011; Dodd et al. 2005). Tertiary amines can be used as catalysts in polyurethane production (Sardon et al. 2015), in the Baylis–Hillman reaction, enhancing the generation of new C–C bonds (Basavaiah et al. 2010) and in water treatment. In water treatment, tertiary amines have been shown to boost the degradation of organic contaminants and promote the disinfection of * Estefania Isaza Ferro [email protected] 1
Department of Bioproducts and Biosystems, Aalto University School of Chemical Engineering, P.O. Box 16300, 00076 Espoo, Finland
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water (Huang and Shah 2018; Basavaiah et al. 2010). It is known that the addition of a tertiary amine such as DABCO (1,4-diazabicyclo[2.2.2]octane) to hypochlorous acid ( HOCl ) produces a highly reactive chlorommonium cation (Rosenblatt et al. 1972). This chloroammonium cation can oxidize saturated structures faster than HOCl (Afsahi et al. 2015; Prütz 1998). Hence, many industries could benefit from faster reactions using chloroammonium cations, including energy-intensive pulp bleaching processes. Nevertheless, finding the right structure that would be stable with the chlorine species, and especially with HOCl and chlorine dioxide ( ClO2 ), has proven challenging. HOCl is a strong oxidant that exists in a pH-dependent equilibrium with chlorine ( Cl2 ) and hypochlorite ion ( ClO− ). At pH
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