Highly-polar layered double hydroxides are efficient adsorbents of low-concentrated trihalomethanes present in water

Abstract

Abstract. Replacement of (Al(OH)6)3- blocks by (AlF6)3- was explored as a strategy to modify the dipolarity of layered double hydroxides materials (LDHs). The presence of fluorine augments the dipolarity/polarizability of LDHs. LDHs were tested as adsorbents of the trihalomethanes CHCl3 and CHBr3 that are present (low concentrated) in water. Fluorinated LDHs were significantly more efficient compared to that without fluorine. Thermal treated fluorinated LDHs are able to remove 95% and 90% of CHCl3 and CHBr3, respectively, present in low concentrated aqueous solutions. The effect of concentration of triahalomethanes, time of contact and structure of adsorbent were explored. Linear isotherms were obtained when un-fluorinated adsorbents were used but the isotherm turns to match that of Freundlich-type when adsorbent contains fluorine. Resumen. La sustitución de iones de (Al (OH)6) 3- por (AlF6)3- se investigó como una estrategia para modificar la dipolaridad de los hidróxidos dobles laminares (HDL). La presencia de flúor aumenta la dipolaridad / polarizabilidad de los HDL. Los HDL se probaron como adsorbentes de los trihalometanos CHCl3 y CHBr3 presentes a bajas concentraciones en agua. Los HDL fluorados fueron significativamente más eficientes en comparación con los que no contenían flúor. Los HDL fluorados tratados térmicamente pueden eliminar 95% y 90% de CHCl3 y CHBr3, respectivamente, presentes en soluciones acuosas a baja concentración. Se examinó el efecto de la concentración de trihalometanos, el tiempo de contacto y la estructura del adsorbente. Se obtuvieron isotermas lineales cuando se usaron adsorbentes no fluorados; en contraste, cuando el adsorbente contiene flúor la isoterma coincide con la de tipo Freundlich.