TEM and SEM identification and characterization of aluminosilicate precipitates from high pH solutions containing Al in contact with quartz
EMSL Project ID
2041
Abstract
We are performing batch kinetics experiments where we place quartz sand in contact with high pH, high ionic strength solutions with varying amounts of Al (90 C). So far we have found that when the Si concentration in solution reaches a certain point, some aluminosilicate substance precipitates. At the onset of precipitation, the Si release changes slope, but the Si concentration continues to increase linearly. The Al concentration, on the other hand, can begin to fluctuate wildly. We think that perhaps an aluminosilicate gel precipitates, and then recrystallizes into some other form. (Some workers in France did some broadly similar experiments on quartz/kaolinite mixtures, and thought they precipitated analcime - a zeolite.) Alternatively, low-Si allophane (an x-ray amorphous aluminosilicate similar in structure to sheet silicates) might be precipitating and then dissolving as the Al concentration goes below an equilibrium value. However, the Al in the allophane structure might preferentially dissolve, and a higher-Si allophane might be left behind. There are other possibilities, but these seem like the most likely at present.The first thing we need is some preliminary data to identify our precipitates at various stages of the reaction. In each sample we have 1-2 g sand and up to several mg of precipitate. We thought perhaps we could send over several samples (3-5), each divided in three. One part would be the bulk reacted sample, another the precipitate separated out as best we can, and another the quartz sand separate, perhaps with some precipitate stuck to the surface. The precipitate separate could be looked at with TEM and electron diffraction, as well as with FESEM. The sand samples could be looked at with the FESEM.
Project Details
Project type
Exploratory Research
Start Date
2000-11-29
End Date
2001-01-01
Status
Closed
Released Data Link
Team
Principal Investigator