Amino acid assisted dehalogenation of carbon tetrachloride by green rust: inhibition of chloroform production

TY - JOUR

T1 - Amino acid assisted dehalogenation of carbon tetrachloride by green rust

T2 - inhibition of chloroform production

AU - Yin, Weizhao

AU - Strobel, Bjarne W.

AU - Hansen, Hans Chr. Bruun

PY - 2017/3/21

Y1 - 2017/3/21

N2 - Layered FeII-FeIII hydroxides (green rusts, GRs) are promising reactants for reductive dechlorination of chlorinated solvents due to high reaction rates and the opportunity to inject reactive slurries of the compounds into contaminant plumes. However, it is necessary to develop strategies that reduce the formation of toxic byproducts such as chloroform (CF). In this study, carbon tetrachloride (CT) dehalogenation by the chloride form of GR (GRCl) was tested in the presence of glycine (GLY) and other selected amino acids. GLY, alanine (ALA), and serine (SER) all resulted in remarkable suppression of CF formation with only ∼10% of CF recovery while sarcosine (SAR) showed insignificant effects. For two nonamino acid buffers, TRIS had little effect while HEPES resulted in a 40 times lower rate constant compared to experiments in which no buffer was added. The FeII complexing properties of the amino acids and buffers caused variable extents of GRCl dissolution which was linearly correlated with CF suppression and dehalogenation rate. We hypothesize that the CF suppression seen for amino acids is caused by stabilization of carbene intermediates via the carbonyl group. Different effects on CF suppression and CT dehalogenation rate were expected because of the different structural and chemical properties of the amino acids. (Figure Presented).

AB - Layered FeII-FeIII hydroxides (green rusts, GRs) are promising reactants for reductive dechlorination of chlorinated solvents due to high reaction rates and the opportunity to inject reactive slurries of the compounds into contaminant plumes. However, it is necessary to develop strategies that reduce the formation of toxic byproducts such as chloroform (CF). In this study, carbon tetrachloride (CT) dehalogenation by the chloride form of GR (GRCl) was tested in the presence of glycine (GLY) and other selected amino acids. GLY, alanine (ALA), and serine (SER) all resulted in remarkable suppression of CF formation with only ∼10% of CF recovery while sarcosine (SAR) showed insignificant effects. For two nonamino acid buffers, TRIS had little effect while HEPES resulted in a 40 times lower rate constant compared to experiments in which no buffer was added. The FeII complexing properties of the amino acids and buffers caused variable extents of GRCl dissolution which was linearly correlated with CF suppression and dehalogenation rate. We hypothesize that the CF suppression seen for amino acids is caused by stabilization of carbene intermediates via the carbonyl group. Different effects on CF suppression and CT dehalogenation rate were expected because of the different structural and chemical properties of the amino acids. (Figure Presented).

KW - Journal Article

U2 - 10.1021/acs.est.6b06244

DO - 10.1021/acs.est.6b06244

M3 - Journal article

C2 - 28244752

SN - 0013-936X

VL - 51

SP - 3445

EP - 3452

JO - Environmental Science & Technology

JF - Environmental Science & Technology

IS - 6

ER -