Transformation of microcystin-LR and olefinic compounds by ferrate(VI): Oxidative cleavage of olefinic double bonds as the primary reaction pathway.

The presence of toxic microcystins in algal-impacted surface waters is a concern for drinking water quality management. In this study, the potential of ferrate(VI) to eliminate microcystins during drinking water treatment was assessed by investigating reaction kinetics, reaction sites, transformation products, and toxicity changes for the oxidation of microcystin-LR (MC-LR) as a representative microsystin. The investigations also included several substructural model compounds of MC-LR, such as cinnamic acid and sorbic acid, to elucidate the major transformation products and pathways of MC-LR and olefinic compounds.

Transformation of ranitidine during water chlorination and ozonation: Moiety-specific reaction kinetics and elimination efficiency of NDMA formation potential.

Ranitidine can produce high yields of N-nitrosodimethylamine (NDMA) upon chloramination and its presence in water resources is a concern for water utilities using chloramine disinfection. This study assessed the efficiency of water chlorination and ozonation in transforming ranitidine and eliminating its NDMA formation potential (NDMA-FP) by determining moiety-specific reaction kinetics, stoichiometric factors, and elimination levels in real water matrices. Despite the fact that chlorine reacts rapidly with the acetamidine and thioether moieties of ranitidine (k>10(8)M(-1)s(-1) at pH 7), the NDMA-FP decreases significantly only when chlorine reacts with the less reactive tertiary amine (k=3×10(3)M(-1)s(-1) at pH 7) or furan moiety (k=81M(-1)s(-1) at pH 7).