%0 Journal Article
%T Fluoride retardation from quartz sand-packed column tests
%A Eduardo Usunoff
%A Pablo Weinzettel
%A Sebasti芍n Dietrich
%J Geoacta
%D 2009
%I Asociaci車n Argentina de Geof赤sicos y Geodestas
%X Inasmuch as both low and high concentrations of F- in groundwater have different detrimental effects on human health (increased dental caries, and mottled enamel or even severe structural bone deformations, respectively), many efforts have focused on the movement of such anion in aqueous systems. It is so because water drinking is the main intake of F- by humans. This paper presents the results of seven dynamic experiments in which solutions of varying [F-], pH, and flow velocities circulated through columns packed with clean quartz sand. The breakthrough data were analyzed by means of a computer code adapted to the estimation of equilibrium and non-equilibrium solute transport parameters from miscible displacement experiments in a steady-state, uniform flow field using a pulse-type or continuous source. It was found that larger retardation factors (R) are associated with low pH, low [F-] in the feed solutions, and larger flow velocities. Such results appear to be related to the form of the F species, the rather weak bond between the adsorbate and the quartz sand, and stronger anion repulsion at low pore velocities. The estimated values for R vary between 1,22 and 1,50, whereas the distribution coefficients were in the range of 0,1 to 0,05 L kg-1. It should be said that the breakthrough curves display hysteresis, leading to a desorption behavior that proceeds faster than the adsorption process. Puesto que tanto valores bajos como altos de F- en las aguas subterr芍neas tienen efectos adversos en la salud de los humanos (mayor cantidad de caries, y manchas del esmalte dental e incluso deformaciones 車seas, respectivamente), han sido muchos los esfuerzos destinados a dilucidar el movimiento de especies fluoradas en ambientes acuosos. Ello es as赤 porque el consumo de agua por parte de seres humanos representa la mayor fuente de ingreso de F-. Este trabajo presenta los resultados de siete experimentos din芍micos en los que soluciones de diferentes [F-], pH y velocidades de flujo percolaron a trav谷s de columnas empacadas con arena cuarzosa. Los datos de la curva de salida fueron analizados con un programa que permite la estimaci車n de par芍metros del transporte de solutos en condiciones de equilibrio o no equilibrio a partir de experimentos de columnas, en un campo de flujo homog谷neo y en estado estacionario, creado por un impulso acotado o continuo del trazador de inter谷s. Se hall車 que los mayores valores del factor de retardo (R) se asociaron a bajos valores de pH, bajas concentraciones de F- de las soluciones de inicio, y mayores velocidades de flujo. Los resul
%K Experimentos de columna
%K Adsorci車n/desorci車n de F-
%K Retardo
%K Column experiments
%K F- adsorption/desorption
%K Retardation
%U http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S1852-77442009000100004