Chlorinated herbicide (triallate) dehalogenation by iron powder.
The reductive degradation of a chlorinated herbicide by iron powder was investigated at lab scale. The studied substrate was triallate (S-2,3,3-trichloroallyl di-isopropyl thiocarbamate) which contains a trichloroethylene moiety potentially reducible by zero-valent iron. Degradation reactions were carried out in batch, at 25 degrees C, in the absence of oxygen, by contacting electrolytic iron powder (size range: 20-50 microm) with a triallate aqueous solution (2.5 mgl(-1)). Herbicide decay, corresponding evolutions of TOC, TOX and chloride ion release were regularly monitored throughout the reactions. Furthermore, the main degradation by-products were identified by HPLC/MS. The results showed that, after 5 days, herbicide degradation extent was about 97% and that the reaction proceeded through the formation of a dechlorinated alkyne by-product (S-2-propinyl di-isopropyl thiocarbamate) resulting from the complete dechlorination of triallate. The subsequent reduction of such an alkyne intermediate gave S-allyl di-isopropyl thiocarbamate as main end by-product. The identified by-products suggested that dechlorination took place mainly via reductive beta-elimination. However, as traces of dichloroallyl di-isopropyl thiocarbamate were also detected, a role, although minor, was assigned even to hydrogenolysis in the overall dechlorination process.
Consiglio Nazionale delle Ricerche, Istituto di Ricerca Sulle Acque, Sezione di Bari, Via Francesco De Blasio, 5-70123 Bari, Italy. angela.volpe@area.ba.cnr.it
Angela
A
Volpe
Antonio
A
Lopez
Giuseppe
G
Mascolo
Antonia
A
Detomaso
D002851:Chromatography, High Pressure Liquid; D008401:Gas Chromatography-Mass Spectrometry; D006540:Herbicides / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D014214:Triallate / Q000737:chemistry*; D014241:Trichloroethylene / Q000737:chemistry
D006540:Herbicides; D014241:Trichloroethylene; D014214:Triallate; D007501:Iron