Modification of arsenic availability in soil through the application of iron micro- and nano-particles
The dispersion of contaminants in soils such as arsenic (As) is an important problem to deal with, for which the interactions between this metalloid and the components of the environment are studied. Iron oxides are highly reactive due to their surface and structural properties, being used in the re...
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| Tipo de recurso: | tesis de maestría |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | Chile |
| OAI Identifier: | oai:repositorio.anid.cl:10533/42550 |
| Acceso en línea: | https://hdl.handle.net/10533/42550 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias Naturales Ciencias Químicas Otras Especialidades de la Química |
| Sumario: | The dispersion of contaminants in soils such as arsenic (As) is an important problem to deal with, for which the interactions between this metalloid and the components of the environment are studied. Iron oxides are highly reactive due to their surface and structural properties, being used in the remediation of pollutants such as arsenic (V). In this work, the effect of iron particles on the availability of As (V) in a soil of volcanic origin, called Ralún and classified as Andisol, is evaluated. For which, ferrihydrite (Fh) particles of micro and nanometric size were synthesized, which were packed together with the soil in leaching columns and exposed to As (V). It was determined that the particles obtained in the synthesis correspond to an iron oxide of the Fh type according to the characterization carried out by Mössbauer spectroscopy. In the experimental design of the leaching tests, two systems were considered that differ in the size distribution of Fh (micro and nanometric, respectively) in a ratio of 10 mg of Fh per 3 g of Ralún soil. From these tests, it is observed that the nanometric-Fh leaches about 79 ± 1% more than the micrometric-sized (Fh-M), which is retained almost entirely (98 ± 1%). Additionally, the effect of iron particles (Fh-M) on the mobility or immobilization of As (V) in the Ralún soil is evaluated, at a flow of 6 and 12 mg L-1 of As (V). When exposing the columns to a flow of 6 mg L-1 , it was observed that when adding 10 mg of Fh, the As (V) is completely retained (99 ± 1%), and when increasing the concentration of As (V) at double (12 mg L-1 ), is retained by 66 ± 4 %, indicating that the sites available for interaction with As (V) are practically fully occupied with a flow of 6 mg L-1 . On the other hand, the available fraction of As (V) was studied, corresponding to the fraction of As (V) that remains available to interact with species and living organisms. This study was carried out by extracting As (V) from the material of the columns of the previous test, using (NH4)2SO4 as extracting agent. For the Fh-soil system that was exposed to a flow of 6 mg L-1 of As (V), a decrease of 50 % of the available As (V) was observed in relation to the Ralún (blank) soil. According to these tests, it is possible to indicate that the incorporation of 3 mg of Fh-M per gram of soil decreases the available As (V) by half, due to the high affinity that exists between the particles of iron oxide type Fh and the As (V). This research study had indicated that Fh particles in a soil of volcanic origin significantly decreases (50%) the availability of arsenic to plants and living organisms. However, when As (V) binds to nanometric-sized, the Fh particles can be mobilized and disseminated towards groundwater. |
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