Effects of humic material on the precipitation of calcium phosphate

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dc.contributor.author Alvarez, Rebeca en_US
dc.contributor.author Evans, Louise en_US
dc.contributor.author Milham, Paul en_US
dc.contributor.author Wilson, Michael en_US
dc.date.accessioned 2009-12-21T02:29:28Z
dc.date.available 2009-12-21T02:29:28Z
dc.date.issued 2004 en_US
dc.identifier 2004000943 en_US
dc.identifier.citation Alvarez Rebeca et al. 2004, 'Effects of humic material on the precipitation of calcium phosphate', Elsevier, vol. 118, pp. 245-260. en_US
dc.identifier.issn 0016-7061 en_US
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 (Ca9(PO4)6?nH2O; ACP), dicalcium phosphate dihydrate (CaHPO4?2H2O; DCPD, also known as brushite), octacalcium phosphate (Ca8H2(PO4)6?5H2O; OCP) and the thermodynamically most stable phase, hydroxyapatite (Ca5(PO4)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. en_US
dc.publisher Elsevier en_US
dc.relation.isbasedon http://dx.doi.org/10.1016/S0016-7061(03)00207-6 en_US
dc.title Effects of humic material on the precipitation of calcium phosphate en_US
dc.parent Geoderma en_US
dc.journal.volume 118 en_US
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.for 060200 en_US
dc.personcode 93096028 en_US
dc.personcode 920832 en_US
dc.personcode 0000016483 en_US
dc.personcode 960346 en_US
dc.percentage 100 en_US
dc.classification.name Ecology en_US
dc.classification.type FOR-08 en_US
dc.description.keywords humic; apatite; calcium phosphate; amorphous; octacalcium phosphate; dicalcium phosphate hihydrate en_US
dc.staffid 960346 en_US

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