期刊
JOURNAL OF CONTROLLED RELEASE
卷 96, 期 1, 页码 29-36出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jconrel.2003.12.031
关键词
controlled release; controlled release glass; CRG; phosphate glass; soluble glass; water treatment agent; corrosion inhibitor; dissolution mechanism; release kinetics
Leach test of a phosphate controlled release glass (CRG) were conducted in aqueous medium under different conditions. Results show that the phosphate CRG dissolves congruently in deionized water. Its dissolution rate is dependent with the solution pH, temperature and concentrations of phosphate ions and calcium ions in the medium, but independent with the stirring speed of the solution. Analysis leads to a conclusion that the dissolution of phosphate glass is a reaction-controlled process. Discussions on the dissolution mechanisms show that the nature of the reaction in the hydrated layer is the dissociation of Na+ ions from the phosphate chains under the attack of the penetrating water molecules. The velocity of formation and development of hydrated layer depends on the diffusion rate of water molecules inside glass. The dissolution is realized by the breakage of P-O-P bonds in the phosphate network within the hydrated layer. The chelating ability of polyphosphate with divalent cations play an important role in the dissolution process of phosphate CRGs and was found responsible for the accelerated or decelerated dissolution of the CRG in sodium hexametaphosphate (SHMP) or CaCl2 solutions, respectively. (C) 2004 Elsevier B.V. All rights reserved.
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