Hydroxyapatite precipitation with Hydron Blue dye

Calcium phosphate, in the form of amorphous hydroxyapatite, precipitates out of neutral water solutions containing calcium and phosphate ions in the form of small agglomerates of 18 mu m average size. When Hydron Blue dye (HB) is added, the insoluble particles gradually agglomerate further to 50 mu m sizes. However, the removal capacity of hydroxyapatite for the dye is increased when the calcium phosphate nucleates and forms in the presence of dye. When coprecipitates form, the particules average 20 mu m size and contain up to 60% organic matter. Nascent calcium phosphate particles have strong capacity for Hydron Blue dye removal. Thus smaller calcium phosphate particles increase the amount of dye molecules in water pollution control. (C) 2016 Elsevier Ltd. All rights reserved.