Please use this identifier to cite or link to this item: https://doi.org/10.1006/jcis.2000.7072
Title: Distinguishing adsorption and surface precipitation of phosphate on goethite (α-FeOOH)
Authors: Li, L.
Stanforth, R. 
Keywords: Adsorption
Goethite
Mobility
Phosphate
Precipitation
Surface charge
Issue Date: 1-Oct-2000
Source: Li, L.,Stanforth, R. (2000-10-01). Distinguishing adsorption and surface precipitation of phosphate on goethite (α-FeOOH). Journal of Colloid and Interface Science 230 (1) : 12-21. ScholarBank@NUS Repository. https://doi.org/10.1006/jcis.2000.7072
Abstract: The reaction between phosphate and goethite changes from adsorption into surface precipitation with no discernible changes in the adsorption isotherm. Distinguishing the two processes, by plotting the loss of phosphate from solution versus final phosphate concentration or based on theoretical calculations, is difficult. This paper presents a method for distinguishing between the two processes based on the change in zeta potential with increasing adsorption. During adsorption, the incoming phosphate results in a more negative surface charge as the more acidic phosphate ion replaces a less acidic surface hydroxyl. The amount of negative charge imparted to the surface should vary linearly with surface coverage for adsorption. Phosphate that is bound to a surface precipitate, on the other hand, imparts a much smaller negative charge to the surface, since there is no change in the character of the surface due to the additional phosphate. Zeta potential measurements of phosphated goethite at varying solution pH values and surface coverages are used to determine the transition point from adsorption to surface precipitation. The transition occurs at dissolved phosphate concentrations much lower than those calculated for phosphate in equilibrium with goethite and iron phosphate. (C) 2000 Academic Press.
Source Title: Journal of Colloid and Interface Science
URI: http://scholarbank.nus.edu.sg/handle/10635/66530
ISSN: 00219797
DOI: 10.1006/jcis.2000.7072
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