Characteristics and mechanisms of phosphate adsorption on dewatered alum sludge

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Title: Characteristics and mechanisms of phosphate adsorption on dewatered alum sludge
Authors: Yang, Y.
Zhao, Y.Q.
Babatunde, A.O.
Wang, L.
Ren, Y.X.
Han, Y.
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Date: Sep-2006
Online since: 2011-09-23T14:59:07Z
Abstract: The adsorption characteristics of phosphate adsorption on the dewatered alum sludge were identified as a function of pH and ion strengths in solution. In addition, adsorption mechanisms were investigated by conducting batch tests on both the hydrolysis and P-adsorption process of the alum sludge, and making a comparative analysis to gain newer insights into understanding the adsorption process. Results show that the adsorption capacity decreased from 3.5 to 0.7 mg-P/g-sludge when the solution pH was increased from 4.3 to 9.0, indicating that adsorption capacity is largely dependent upon the pH of the system. The results of the competitive adsorption between phosphate and typical anions found in wastewater, such as SO42- and Cl-, onto alum sludge reveal that alum sludge can selectively adsorb phosphate ions. The insignificant effect of SO42- and Cl- on P-adsorption capacity indicates that phosphate adsorption is through a kind of inner-sphere complex reaction. During the adsorption process, the decrease of phosphate concentration in solution accompanied with an increase in pH values and concentrations of SO42-, Cl- and TOC (total organic carbon) suggests that phosphate replaced the functional groups from the surface of alum sludge which infers that ligand exchange is the dominating mechanism for phosphate removal. At the same time, the simultaneous decreases in PO43- and total aluminium concentration in solution indicate that chemical reaction and precipitation are other mechanisms of phosphate removal.
Funding Details: Other funder
Type of material: Journal Article
Publisher: Elsevier
Journal: Separation and Purification Technology
Volume: 51
Issue: 2
Start page: 193
End page: 200
Copyright (published version): 2006 Elsevier B.V.
Keywords: Adsorption mechanismsAlum sludgeLigand exchangePhosphate removalSurface complex
Subject LCSH: Phosphates--Absorption and adsorption
Water treatment plant residuals
Water--Purification--Phosphate removal
Ligand exchange chromatography
DOI: 10.1016/j.seppur.2006.01.013
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Language: en
Status of Item: Peer reviewed
Appears in Collections:Centre for Water Resources Research Collection
Urban Institute Ireland Research Collection
Critical Infrastructure Group Research Collection
Civil Engineering Research Collection

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