Homogeneous and Heterogeneous Oxidation of Nitrilotrismethylenephosphonic Acid (NTMP) in the Presence of Manganese(II, III) and Molecular Oxygen

Abstract

In the absence of oxygen, NTMP (nitrilotrismethylenephosphonic acid) is oxidized by aqueous suspensions of the Mn III -containing mineral manganite (MnOOH), yielding iminodimethylenephosphonic acid (IDMP) as the sole phosphonate-containing product, along with orthophosphate and two equivalents of Mn II . Hence, both C-P and C-N bond cleavage take place. The reaction proceeds via formation of a Mn III -NTMP surface complex and oxidation of NTMP by Mn III via a carbon-centered methylene radical. Mn II strongly inhibits the reaction, presumably by competition for available surface sites. Homogeneous NTMP oxidation in Mn IIand O 2 -containing solutions yields IDMP, formate, phosphate, and hydrogen peroxide. Interception of the methylene radical by O 2 leads to N-formyl-IDMP and a second not-identified product. The dual presence of MnOOH and O 2 yields autocatalytic NTMP oxidation, owing to the generation of dissolved Mn II . Although the ultimate oxidants in the Mn II -NTMP-O 2 and MnOOH-NTMP systems are different (O 2 versus Mn III ), both oxidation reactions begin with C-N bond cleavage. This finding supports the hypothesis that Mn III is generated in the Mn II -NTMP-O 2 system.

Manganese-catalyzed degradation of phosphonic acids

“…A decrease in NTMP concentrations over time was observed in oxygen-free manganite-suspensions at pH 7 (Nowack and Stone 2002). The diphosphonate IDMP was the sole phosphonate-containing product.…”

“…Hence, any formaldehyde produced was less than 0.4% of the amount predicted from observed IDMP concentrations. Instead, formic acid was detected, an Adapted with permission from Nowack and Stone (2002). Copyright (2000) American Chemical Society oxidation product of formaldehyde.…”

“…1 Structures of the compounds discussed in this article highlighted the importance of Mn(II)-phosphonate complex formation in promoting degradation. Further evidence comes from experiments involving the Mn(III) mineral manganite (MnOOH) (Nowack and Stone 2002). The breakdown products of the Mn(II)-catalyzed degradation have been analyzed in wastewater from textile industry using a newly developed liquid chromatographic method (Nowack 2002b).…”

The citric acid–MnIII,IVO2(birnessite) reaction. Electron transfer, complex formation, and autocatalytic feedback

“…Natural samples invariably contain a mixture of the two oxidation states. Mn III,IV (hydr)oxides are stronger oxidants than Fe III (hydr)oxides, which explains their importance as oxidants of inorganic species (Eary and Rai, 1987;Tournassat et al, 2002) and organic compounds (Stone and Morgan, 1984a,b;Stone, 1987;Xyla et al, 1992;McArdell et al, 1998;Klewicki and Morgan, 1999;Nowack and Stone, 2002), including chelating agents (Xyla et al, 1992;McArdell et al, 1998;Klewicki and Morgan, 1999;Nowack and Stone, 2002).…”

Synthesis of manganese oxide supported on mesoporous titanium oxide: Influence of the block copolymer

“…They are also good candidates as catalysts in water treatment applications [23][24][25]. These oxides were evaluated in the catalytic wet air oxidation reaction when the elimination of organic pollutants occurs in the liquid phase using oxygen as the oxidant [3,[26][27][28][29][30][31].…”