Effects of humic material on the precipitation of calcium phosphate

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dc.contributor.author Alvarez, R
dc.contributor.author Evans, LA
dc.contributor.author Milham, PJ
dc.contributor.author Wilson, MA
dc.date.accessioned 2009-12-21T02:29:28Z
dc.date.issued 2004-02
dc.identifier.citation Geoderma, 2004, 118 (3-4), pp. 245 - 260
dc.identifier.issn 0016-7061
dc.identifier.other C1 en_US
dc.identifier.uri http://hdl.handle.net/10453/3627
dc.description.abstract Soil organic acids such as humic and fulvic acids can play an important role in influencing inorganic phosphate availability in P-fertilized soils by inhibiting formation of thermodynamically stable calcium phosphates. Calcium phosphate phases which are important in these systems may include amorphous calcium phosphate (Ca 9(PO 4) 6·nH 2O; ACP), dicalcium phosphate dihydrate (CaHPO 4 ·2H 2O; DCPD, also known as brushite), octacalcium phosphate (Ca 8H 2(PO 4) 6·5H 2O; OCP) and the thermodynamically most stable phase, hydroxyapatite (Ca 5(PO 4) 3OH; HAp). In this study, the formation of these phases in the presence of soil humic acids derived from the Sydney Basin in New South Wales, Australia has been examined using the combined techniques of pH-stat autotitration, Fourier transform infrared (FTIR) and laser Raman spectroscopy, as well as X-ray diffraction (XRD) and elemental analyses. Under conditions of high supersaturation at a pH of 7. 4 and a temperature of 25°C, it was found that these soil humics delay the transformation of unstable ACP to thermodynamically more stable OCP and thence to an apatitic phase resembling poorly crystalline HAp. At the lower pH of 5.7, and in the presence of humic acids, ACP was also precipitated initially. However, this was in contrast to the humic-free solutions which produced DCPD. ACP produced in the presence of humic materials persisted longer than DCPD in their absence, before ultimately hydrolyzing to OCP. Modes of humic-calcium phosphate interaction are discussed. It has been concluded that humic materials are geologically relevant inhibitors of calcium phosphate transformation and that they may modify the availability of phosphorus in soils by changing crystallisation behaviour from solution. © 2003 Elsevier B.V. All rights reserved.
dc.language eng
dc.relation.isbasedon 10.1016/S0016-7061(03)00207-6
dc.title Effects of humic material on the precipitation of calcium phosphate
dc.type Journal Article
dc.description.version Published
dc.parent Geoderma
dc.journal.volume 3-4
dc.journal.volume 118
dc.publocation Amsterdam en_US
dc.identifier.startpage 245 en_US
dc.identifier.endpage 260 en_US
dc.cauo.name SCI.Faculty of Science en_US
dc.conference Verified OK en_US
dc.conference 4th IEEE International Conference on Advanced Learning Technologies
dc.for 0602 Ecology
dc.personcode 920832
dc.personcode 960346
dc.personcode 0000016483
dc.percentage 100 en_US
dc.classification.name Ecology en_US
dc.classification.type FOR-08 en_US
dc.date.activity 2004-08-30
dc.location.activity Joensuu, FINLAND
dc.description.keywords Amorphous
dc.description.keywords Apatite
dc.description.keywords Calcium phosphate
dc.description.keywords Dicalcium phosphate dihydrate
dc.description.keywords Humic
dc.description.keywords Octacalcium phosphate
pubs.embargo.period Not known
pubs.organisational-group /University of Technology Sydney
pubs.organisational-group /University of Technology Sydney/Faculty of Science
utslib.copyright.status Closed Access
utslib.copyright.date 2015-04-15 12:17:09.805752+10
pubs.consider-herdc true
utslib.collection.history Closed (ID: 3)
utslib.collection.history School of Chemistry and Forensic Science (ID: 339)
utslib.collection.history School of Chemistry and Forensic Science (ID: 339)

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