Pereira Rodrigo C, da Costa Antonio C S, Ivashita Flávio F, Paesano Andrea, Zaia Dimas A M
Laboratório de Química Prebiótica, Departamento de Química-CCE, Universidade Estadual de Londrina, 86051-990, Londrina, PR, Brazil.
Departamento de Agronomia-CCA, Universidade Estadual de Maringá, 87020-900, Maringá, PR, Brazil.
Heliyon. 2020 Mar 6;6(3):e03532. doi: 10.1016/j.heliyon.2020.e03532. eCollection 2020 Mar.
Glyphosate (N- (phosphonomethyl) glycine) is one of the most widely used herbicides in the world. In the literature, there are several studies describing the interaction between glyphosate and clay minerals. However, there is a lack of data of this interaction in marine environments. In this research, we examined the adsorption of glyphosate onto montmorillonite in the presence of artificial seawater. Mössbauer data showed that the interaction of the phosphonate group of glyphosate with Fe of montmorillonite prevents its oxidation to Fe. X-ray diffractograms showed that glyphosate adsorption takes place only onto the montmorillonite surface and not in its interlayers. Infrared spectroscopy data demonstrate that the interaction between glyphosate and montmorillonite could be through the amino group. FT-IR spectra of aqueous solutions of salts of seawater showed that Ca interacts with glyphosate of the phosphonate group, thus causing an increase in its adsorption onto montmorillonite. However, glyphosate dissolved in 0.50 mol L NaCl and 0.034 mol L-1MgCl2 solutions showed the lowest adsorption onto montmorillonite. In addition, the adsorption of glyphosate onto montmorillonite decreased when the NaCl concentration increased. The results fitted the Sips isotherm model, probably because the Ca interacts with glyphosate, making the adsorption process more homogeneous. Thus, n values for Freundlich and Sips isotherm models decreased with an increase in ionic strength. Glyphosate and ions of artificial seawater increased the pH of montmorillonite.
草甘膦（N-（膦酰基甲基）甘氨酸）是世界上使用最广泛的除草剂之一。在文献中，有几项研究描述了草甘膦与粘土矿物之间的相互作用。然而，在海洋环境中缺乏这种相互作用的数据。在本研究中，我们研究了在人工海水存在下草甘膦在蒙脱石上的吸附情况。穆斯堡尔数据表明，草甘膦的膦酸基团与蒙脱石的铁相互作用可防止其氧化成铁。X射线衍射图表明，草甘膦仅吸附在蒙脱石表面，而不是其层间。红外光谱数据表明，草甘膦与蒙脱石之间的相互作用可能是通过氨基进行的。海水盐溶液的傅里叶变换红外光谱表明，钙与膦酸基团的草甘膦相互作用，从而导致其在蒙脱石上的吸附增加。然而，溶解在0.50 mol L氯化钠和0.034 mol L-1氯化镁溶液中的草甘膦在蒙脱石上的吸附最低。此外，当氯化钠浓度增加时，草甘膦在蒙脱石上的吸附减少。结果符合Sips等温线模型，可能是因为钙与草甘膦相互作用，使吸附过程更加均匀。因此，Freundlich和Sips等温线模型的n值随离子强度的增加而降低。草甘膦和人工海水离子提高了蒙脱石的pH值。
