Coadsorption of Cu(II) and glyphosate at the water–goethite (α-FeOOH) interface: molecular structures from FTIR and EXAFS measurements
2003 (English)In: Journal of Colloid and Interface Science, Vol. 262, no 1, 38-47 p.Article in journal (Refereed) Published
The coadsorption of Cu(II) and glyphosate (N-(phosphonomethyl)glycine, abbreviated to PMG) at the water–goethite interface was studied by means of batch adsorption experiments, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The system was investigated over the pH range 3–9 and at total concentrations of 0.9 μmol and 2.2 μmol Cu(II) and PMG per m2 of goethite. The collective quantitative and spectroscopic results show that Cu(II) and PMG directly interact at the water–goethite interface to form ternary surface complexes. Two predominating complexes have been identified. At pH 4 the IR and CuK-edge EXAFS data indicate a molecular structure where the phosphonate group of PMG bonds monodentately to the surface in an inner sphere mode, while carboxylate and amine groups coordinate to Cu(II) to form a 5-membered chelate ring. Hence, at pH 4, Cu(II) and PMG form a ternary surface complex on goethite with the general structure goethite–PMG–Cu(II). At the highest pH investigated (pH 9), the carboxylate group is still coordinated to Cu(II) but the phosphonate group is present in a relatively free, noncoordinated and/or disordered state. Although the spectroscopic data are not conclusive they indicate the formation of ternary surface complexes with the molecular architecture goethite–Cu(II)–PMG at high pH.
Place, publisher, year, edition, pages
2003. Vol. 262, no 1, 38-47 p.
Glyphosate, Copper, Coadsorption, Surface complexes, FTIR, EXAFS
IdentifiersURN: urn:nbn:se:umu:diva-9288DOI: doi:10.1016/S0021-9797(03)00207-8OAI: oai:DiVA.org:umu-9288DiVA: diva2:148959