AVENA marcelo Javier
A real time in situ ATR-FTIR spectroscopic study of glyphosate desorption from goethite as induced by phosphate adsorption: Effect of surface coverage
CAROLINA WAIMAN; MARCELO AVENA; ALBERTO REGAZZONI; GRACIELA ZANINI
JOURNAL OF COLLOID AND INTERFACE SCIENCE
ACADEMIC PRESS INC ELSEVIER SCIENCE
Lugar: Amsterdam; Año: 2013 vol. 394 p. 485 - 489
The desorption of glyphosate from goethite as induced by the adsorption of phosphate was investigated by attenuated total reﬂectance Fourier transform infrared (ATR-FTIR) spectroscopy in combination with adsorption isotherms. Desorption of glyphosate was very low in the absence of phosphate. Addition of phosphate promoted glyphosate desorption. At low initial surface coverages, added phosphate adsorbed on free surface sites, mainly, displacing a small amount of glyphosate. At high initial surface coverages, on the contrary, phosphate adsorption resulted in a signiﬁcant glyphosate desorption. In the latter conditions, the ratio desorbed glyphosate to adsorbed phosphate was 0.60. The desorption process can be explained by assuming that phosphate adsorbs ﬁrst forming a monodentate mononuclear complex, which rapidly evolves into a bidentate binuclear complex that displaces glyphosate.