Laserfiche WebLink
• <br />150 <br />FeOOH Am = 61 KI = 0.021 <br />50 <br />40 <br />a <br />E <br />30 <br />c <br />O 20 <br />10 <br />c <br />0 <br />V 0 <br />0 10 20 30 40 50 • <br />Figure 4 - Langmuir lsothem for Sb(+3) adsorption onto goethite (Langmuir <br />constants from Watkins et al., 2006). <br />The adsorption of Sb(+3) as illustrated in Figure 4 can be understood by imagining a <br />"clean" soil or sediment which is subjected to waters with increasing Sb(+3) <br />concentrations (such as a with the expansion of an antiniony-bearing groundwater <br />plume). As the solution Sb(+3) concentrations increase, increasingly greater amounts of <br />Sb(+3) can be "forced" onto the solid surface. The steep part of the curve where soils <br />Sb(+3) concentration increase rapidly describes the process. As the Sb(+3) concentrations <br />on the soil continue to increase, a point is eventually reached where the solid surfaces <br />are completely saturated with Sb(+3) and there is no more capacity for additional <br />adsorption. No matter how high the dissolved Sb(+3) concentrations become, the solid <br />Sb(+3) concentration remains constant. The flat part of the curve describes the saturation <br />point of the solid. The Langmuir Am constant is the adsorption capacity and determines <br />the level of the flat portion of the curve, while the KI constant determines the rate at <br />which Am is reached (the steepness of the initial segment of the curve). <br />Sb(+3) and Sb(+S) have also been found to be associated with the humic fractions of soil, <br />(Steel, et al., 2007), c iwgcstin?- that antim?)m, id wrb, to ' Oil 0rt;.1T1iC matter. 1 lk)vwcvcr.