...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Crystal growth & design >Precipitation of calcium phosphate from simulated milk ultrafiltrate solutions
【24h】

Precipitation of calcium phosphate from simulated milk ultrafiltrate solutions

机译：模拟牛奶超滤液溶液中磷酸钙的沉淀

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The present work deals with the influence of pH and temperature on the spontaneous precipitation of calcium phosphate from simulated milk ultrafiltrate (SMUF) solutions. The pH range investigated is 5.7-7.0, and the temperature varied from 55 to 75 degrees C. It was found that the precipitates were prisms of hydroxyapatite (HAP) with low crystallinity preceded by amorphous calcium phosphate (ACP). Crystallinity improved with solution aging. Microscopic particles in the range of 200 nm were obtained at relatively high supersaturation (pH = 6.8), whereas at relatively low supersaturation (pH = 6.0), aggregates in the range of 1 mu m were formed. Moreover, it was found that although the SMUF solution is also supersaturated with respect to magnesium phosphate, no magnesium salt was identified in the precipitates, thus precluding the coprecipitation of magnesium phosphate. At the same temperature, the supersaturation was regulated by adjusting the solution pH. Kinetics study of precipitation showed a parabolic dependence of the (initial) rates on the solution supersaturation, suggesting a surface diffusion-controlled mechanism with activation energy equal to 96 kJ mol(-1). The rates of precipitation were significantly reduced in the presence of citrate ions due to the decrease of the solution supersaturation caused by complexation of citrates with Ca2+ ions. Additionally, a decreasing effect of citrates on the precipitation rate resulted from the adsorption of these species on the formed crystals, blocking some active sites of crystal growth and diminishing the constant of precipitation rate.
机译：本工作涉及pH和温度对模拟超滤牛奶（SMUF）溶液中磷酸钙自发沉淀的影响。研究的pH范围是5.7-7.0，温度在55至75℃之间变化。发现沉淀物是具有低结晶度的羟基磷灰石（HAP）的棱柱，其前是无定形磷酸钙（ACP）。结晶度随溶液老化而提高。在较高的过饱和度（pH = 6.8）下获得了200 nm范围内的微观颗粒，而在较低的过饱和度（pH = 6.0）下获得了1μm范围内的聚集体。此外，发现尽管SMUF溶液相对于磷酸镁也过饱和，但在沉淀物中未发现镁盐，因此排除了磷酸镁的共沉淀。在相同温度下，通过调节溶液的pH值来调节过饱和度。沉淀的动力学研究表明（初始）速率对溶液过饱和具有抛物线依赖性，这表明活化能等于96 kJ mol（-1）的表面扩散控制机制。由于柠檬酸根与Ca2 +离子络合导致溶液过饱和度降低，因此在柠檬酸根离子存在下，沉淀速率显着降低。另外，柠檬酸盐对沉淀速率的降低作用是由于这些物质在形成的晶体上的吸附，阻止了晶体生长的一些活性位点，并降低了沉淀速率的常数。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号