کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4432957 | 1619944 | 2007 | 11 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Inhibition of calcium phosphate precipitation under environmentally-relevant conditions
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کلمات کلیدی
موضوعات مرتبط
علوم زیستی و بیوفناوری
علوم محیط زیست
شیمی زیست محیطی
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چکیده انگلیسی
Precipitation of Ca phosphates plays an important role in controlling P activity and availability in environmental systems. The purpose of this study was to determine inhibitory effects on Ca phosphate precipitation by Mg2+, SO42â, CO32â, humic acid, oxalic acid, biogenic Si, and Si-rich soil clay commonly found in soils, sediments, and waste streams. Precipitation rates were determined by measuring decrease of P concentration in solutions during the first 60Â min; and precipitated solid phases identified using X-ray diffraction and electron microscopy. Poorly-crystalline hydroxyapatite (HAP: Ca5(PO4)3OH) formed in control solutions over the experiment period of 24Â h, following a second-order dependence on P concentration. Humic acid and Mg2+ significantly inhibited formation of HAP, allowing formation of a more soluble amorphous Ca phosphate phase (ACP), and thus reducing the precipitation rate constants by 94-96%. Inhibition caused by Mg2+ results from its incorporation into Ca phosphate precipitates, preventing formation of a well-crystalline phase. Humic acid likely suppressed Ca phosphate precipitation by adsorbing onto the newly-formed nuclei. Presence of oxalic acid resulted in almost complete inhibition of HAP precipitation due to preemptive Ca-oxalate formation. Carbonate substituted for phosphate, decreasing the crystallinity of HAP and thus reducing precipitation rate constant by 44%. Sulfate and Si-rich solids had less impact on formation of HAP; while they reduced precipitation in the early stage, they did not differ from the control after 24Â h. Results indicate that components (e.g., Mg2+, humic acid) producing relatively soluble ACP are more likely to reduce P stability and precipitation rate of Ca phosphate in soils and sediments than are components (e.g., SO42â, Si) that have less effect on the crystallinity.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Science of The Total Environment - Volume 383, Issues 1â3, 20 September 2007, Pages 205-215
Journal: Science of The Total Environment - Volume 383, Issues 1â3, 20 September 2007, Pages 205-215
نویسندگان
Xinde Cao, Willie G. Harris, Manohardeep S. Josan, Vimala D. Nair,