Although, glyphosate (N-(phosphonomethyl) glycine) is one of the most widely used herbicides in the world, its interaction with poorly crystalline iron oxides, such as ferrihydrite, is not well studied. In this research, we examined the adsorption of glyphosate onto ferrihydrite using infrared spectroscopy (FT-IR), electron paramagnetic resonance spectroscopy (EPR), adsorption kinetic models and adsorption isotherm models. The effect of pH and sodium chloride concentration on the adsorption of glyphosate onto ferrihydrite as well as the effect of extractors (CaCl2 0.010 mol L−1 and Mehlich) on the desorption of glyphosate were also evaluated. There are two important findings described in this work. First, 84% of adsorbed glyphosate strongly interacted to ferrihydrite as an inner-sphere complex and phosphate and amine groups are involved in this interaction. Second, an increase of sodium chloride salt concentration increased the adsorption of glyphosate onto ferrihydrite. The non-linear Langmuir model and pseudo second order model showed a good agreement of theoretical limit of glyphosate adsorbed onto ferrihydrite, 54.88 µg mg−1 and 48.8 µg mg−1, respectively. The adsorption of glyphosate onto ferrihydrite decreased when the pH increased. Under the conditions used in this work, EPR spectra did not show dissolution of ferrihydrite. Surface area, pore volume and pHpzc of ferrihydrite decreased after adsorption of glyphosate.Electronic supplementary materialThe online version of this article (10.1186/s12932-019-0063-1) contains supplementary material, which is available to authorized users.

No abstract

Interaction between adenine, salts, water and Fe-ZSM-5 zeolite surface. Zeolite is represented by 10 ring straight channel. Figure adapted from www.iza-structure.org/databases (accessed on 08/31/2015).

Goethite (α‐FeOOH) is by definition an antiferromagnetic (AFM) material. In the present work an investigation of the magnetic properties of goethite is performed, studying the magnetic component of this material in different samples and relating these properties with its structural and morphological characteristics. Samples are synthetized in two distinct ways in order to generate solids with different degrees of structural defects and imperfections. Electron spin resonance (ESR) data show that the sample synthesized in a faster procedure, most susceptible to defects and imperfections (GC sample), shows an area under the ESR line ≈20 times higher than the sample set for a lower incidence of defects (GD sample). Experiments with heat‐treated samples at 150 °C show a reduction in the number of spins which contributed to ESR signal for the GC sample. Considering data of thermogravimetry (TGA), X‐ray diffraction (XRD), and Mössbauer spectroscopy, the differences observed in ESR analysis are attributed to a magnetic mismatch in the AFM structure caused by the incidence of local defects, more common in GC sample. Results of heat‐treated samples are associated to an increase in the exchange interaction between grains, which reduces the number of mismatched spins and favors the AFM arrangement.

No abstract