title: EDTA degradation induced by oxygen activation in a zerovalent iron/air/water system.
abstract: A method for the removal of ethylenediaminetetraacetic acid (EDTA) at room temperature and 1 atm is demonstrated. EDTA (1 mM, 50 mL) containing 2.5 g of granular zerovalent iron (ZVI) (20-40 mesh) was degraded in 2.5 h. Using a recently developed form of O2 activation, reactive oxygen species are generated in situ, resulting in the degradation of EDTA when complexed with FeII. ESI-MS measurements indicate that degradation of EDTA yields low-molecular carboxylic acids. The presence of oxygen is crucial: the observed pseudo-first-order rate constants for EDTA removal are kobs = 1.02 h(-1) (kSA = 1.85 +/- 0.046 L h(-1) m(-2)) and kobs = 0.04 h(-1) (kSA = 0.00724 +/- 0.002 L h(-1) m(-2)) under air and under N2 purge, respectively. kSA represents surface area normalized rate constants. Large excesses of EDTA in the reaction mixture slowthe rate of degradation. Increasing the concentration of EDTA from 1.0 to 10.0 mM while holding all other parameters constant gave observed rates of kobs = 1.02 +/- 0.26 h(-1) (kSA = 1.85 +/- 0.046 L h(-1) m(-2)) and kobs = 0.044 +/- 0.01 h(-1) (kSA = 0.00796 +/- 0.002 L h(-1) m(-2)), respectively. The rate-limiting step is determined to be homogeneous oxygen activation.
authors.affiliation: Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343, USA.
authors.forename: Christina E
authors.initials: CE
authors.lastname: Noradoun
authors.forename: I Francis
authors.initials: IF
authors.lastname: Cheng
mesh_terms: D000388:Air; D002264:Carboxylic Acids / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000737:chemistry* / Q000494:pharmacology; D005609:Free Radicals; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D011312:Pressure; D017382:Reactive Oxygen Species; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays; D014867:Water
chemical_list: D002264:Carboxylic Acids; D002614:Chelating Agents; D005609:Free Radicals; D017382:Reactive Oxygen Species; D014867:Water; D004492:Edetic Acid; D007501:Iron; D010100:Oxygen