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Research article - Peer-reviewed, 2020

Adsorption of phosphate by halloysite (7 angstrom) nanotubes (HNTs)

Gray-Wannell, Nia; Holliman, Peter J.; Greenwell, H. Christopher; Delbos, Evelyne; Hillier, Stephen


The adsorption and retention of phosphates in soil systems is of wide environmental importance, and understanding the surface chemistry of halloysite (a common soil clay mineral) is also of prime importance in many emerging technological applications of halloysite nanotubes (HNTs). The adsorption of phosphate anions on tubular halloysite (7 angstrom) has been studied to gain a greater understanding of the mechanism and kinetics of adsorption on the surface of HNTs. Two well-characterized tubular halloysites with differing morphologies have been studied: one polygonal prismatic and one cylindrical, where the cylindrical form has a greater surface area and shorter tube length. Greater phosphate adsorption of up to 42 mu mol g(-1) is observed on the cylindrical halloysite when compared to the polygonal prismatic sample, where adsorption reached a maximum of just 15 mu mol g(-1) compared to a value for platy kaolinite (KGa-2) of 8 mu mol g(-1). Phosphate adsorption shows strong pH dependence, and the differences in phosphate sorption between the prismatic and cylindrical morphologies suggest that phosphate absorption does not occur at the same pH-dependent alumina edge sites and that the lumen may have a greater influence on uptake for the cylindrical form.


adsorption; anion-exchange capacity; halloysite nanotube; HNT; phosphate

Published in

Clay Minerals
2020, volume: 55, number: 2, pages: 184-193

Authors' information

Gray-Wannell, Nia
Swansea University
Gray-Wannell, Nia
James Hutton Institute
Holliman, Peter J.
Swansea University
Greenwell, H. Christopher
Durham University
Delbos, Evelyne
James Hutton Institute
James Hutton Institute
Swedish University of Agricultural Sciences, Department of Soil and Environment

UKÄ Subject classification

Materials Chemistry

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