Potentiometric Study of the Formation of Magnesium Potassium Phosphate Hexahydrate
Publication: Journal of Materials in Civil Engineering
Volume 24, Issue 5
Abstract
The formation process of magnesium potassium phosphate hexahydrate was studied by monitoring the pH development of the system. It is found that a typical potentiometric curve goes through several rises and drops, forming two local peaks and two local valleys, before reaching a plateau at pH of approximately 10.5. The characteristic points of the curve are identified and then utilized to distinguish the different reaction stages during the formation of the hexahydrate. By comparing the potentiometric curves of the ternary systems with different molar ratios, and from X-ray diffractometry analysis of the precipitates extracted at different stages, the formation of the hexahydrate most likely proceeds stepwise through two crystalline intermediates, namely and . The thermal behavior of the formation process of magnesium potassium phosphate hexahydrate, including the formation and transformation among the intermediates and final product, is further verified by thermodynamic calculation. Finally, the morphologies of the different crystalline phases of the ternary system are examined by a scanning electron microscope (SEM).
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Acknowledgments
The partial financial support from the China Ministry of Science and Technology under grant 2009CB623200 and the Hong Kong Research Grant Council under grant 615810 are gratefully acknowledged.
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Published In
Journal of Materials in Civil Engineering
Volume 24 • Issue 5 • May 2012
Pages: 586 - 591
Copyright
© 2012. American Society of Civil Engineers.
History
Received: Apr 21, 2011
Accepted: Oct 27, 2011
Published online: Apr 16, 2012
Published in print: May 1, 2012
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