Abstract
Se ha investigado el uso de la resina de intercambio catiónico Lewatit TP208 en la eliminación de hierro(II) de disoluciones acuosas. En esta eliminación, se han considerado varias variables experimentales, incluyendo, la velocidad de agitación aplicada al sistema, la temperatura, el pH de la disolución acuosa y la dosificación de la resina. Para velocidades de agitación incluidas en el intervalo 300-1200 min-1, el proceso de intercambio catiónico responde al modelo de difusión en la disolución acuosa. El aumento de la temperatura, entre 20 y 60 ºC, va asociado a un aumento de la concentración de hierro(II) cargado en la resina, por lo que el sistema tiene un carácter endotérmico. La variación del pH del medio acuoso hacia pH ácidos (desde 5 a 1) da lugar a una disminución en la carga del metal en la resina. Asimismo, la dosificación de la resina Lewatit TP208 afecta a la eliminación del hierro(II) de la disolución acuosa, los resultados experimentales se ajustan a la isoterma de Freundlich. Los modelos cinéticos asociados a este sistema dependen también de la dosificación de la resina: usando la concentración de resina más alta (1 g·L-1) los datos experimentales se ajustan (r2= 0,999) al modelo de pseudo-segundo orden, mientras que con la concentración de resina más baja (0,13 g·L-1) el modelo cinético es el primer-orden (r2= 0,997). Los resultados experimentales obtenidos con la resina Lewatit TP208 se han comparado con los obtenidos con otras resinas de intercambio catiónico y con el uso de nanotubos de carbono de pared múltiple. El hierro(II), cargado en la resina, puede ser eluido mediante el uso de disoluciones ácidas.
Highlights
The removal of toxic-hazardous metallic species presents in wastewaters, liquid effluents and, in general, aqueous environments is of the upmost importance due to its social impact and its implications on human health and the environment
Iron can be present as iron(II), iron(III) or a mixture of both, and while both are essential for life, an excess in their ingesta is often accompanied with the increase of the formation of reactive oxygen species in cells, increasing, as a consequence of the above, the risk of cancer, heart disease, haemochromatosis; besides, iron accumulation in the central nervous system is connected with other serious illnesses
The excess of the presence of iron(II) and (III) ions in the body comes from their use in agriculture and industry, that eventually ends into contaminated rivers, ponds, lakes, etc
Summary
The removal of toxic-hazardous metallic species presents in wastewaters, liquid effluents and, in general, aqueous environments is of the upmost importance due to its social impact and its implications on human health and the environment. The removal of iron(II) from aqueous solutions had been of interest for various research groups, and several ion exchange resins and/or adsorbents were used recently in this role, i.e. 732-type strong acid cation exchange resin, in an ascorbic acid and EDTA medium, effectively loaded Fe(II) at acidic pH values (Zhou et al, 2018), multiwalled carbon nanotubes modified with EDTA, and containing amino and carboxyl groups removed Fe(II) from aqueous solutions (Desouky, 2018), whereas nanosized calcium deficient hydroxyapatite was other material used in the removal of this element from solutions (Van Dat et al, 2019). From Fe2+-loaded resin, by HCl solutions is presented
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