Adsorption of glyphosate on variable-charge, volcanic ash-derived soils

Glyphosate (N-phosphonometylglycine) is widely used due to its broad spectrum of activity and nonselective mode of action. In Chile it is the most used herbicide, but its adsorption behavior in the abundant and widespread variable charge soils is not well understood. In this study, three volcanic ash-derived soils were selected, including Andisols (Nueva Braunau and Diguillin) and Ultisols (Collipulli), to evaluate the adsorption kinetics, equilibrium isotherms, and the effect of pH in glyphosate adsorption. The influence of glyphosate on soil phosphorus retention was also studied. Glyphosate was rapidly and strongly adsorbed on the selected soils, and adsorption isotherms were well described by the Freundlich relationship with strong nonlinearity (n(fads)& < 0-5). The n(fads) values were consistently higher than n(fdes) values, suggesting strong hysteresis. Adsorption (K,,) increased strongly when pH decreased. The presence of glyphosare (3200 mu g mL(-1)) changed the adsorption behavior of phosphate at its maximum adsorption capacity. Andisol soils without the addition of glyphosate had similar mean K(ads) values for Nueva Braunau (5.68) and Diguillin (7.38). Collipulli had a mean K(ads) value of 31.58. During the successive desorption steps, glyphosate at the highest level increased K(ads), values for phosphate in the Andisol soils but I-lad little effect in the Ultisol soil. This different behavior was probably due to the irreversible Occupation of some adsorption sites by glyphosate in the Ultisol soil attributed to the dominant Kaolinite mineral. Results from this study suggest that in the two types of volcanic soils, different mechanisms are involved in glyphosate and phosphate adsorption and that long-term use of glyphosate may impose different effects on the retention and availability of phosphorus. Volcanic ash-derived soils have a particular environmental behavior in relation to the retention of organic contaminants, representing an environmental substrate that may become highly Polluted over time due to intensive agronomic uses

Imogolite: A nanotubular aluminosilicate: Synthesis, derivatives, analogues, and general and biological applications

Imogolite is an aluminosilicate mineral originally found in volcanic ash derived soils. Through the use of chemical synthesis methods this mineral has been successfully synthesized and a number of modified similar nanomaterials have also been produced. Due to its nanotubular arrangement this mineral shows a similar structure to carbon nanotubes and as such has been investigated for possible applications in a range of fields like polymer composites, gas storage, adsorption and catalysis. This review will start with an introduction to the basic characteristics of imogolite, followed by the synthetic methods of production, techniques for the production of composite and hybrid materials, characterization, potential applications, and, finally, biological applications, focusing particularly on composites with biological molecules and interactions with living cells as well as toxicological activity. This journal i