The effect of trace metal extraction procedures on clay minerals

Abstract

Samples of American Petroleum Institute clays kaolinite #4, montmorillonite #20 and illite #35 were treated with. 8 different trace metal extraction procedures. X‐ray diffraction patterns of oriented samples of the clays were prepared before and after sample treatment. After treatment, the extraction fluids were separated from the clay residue and analyzed for Si, Al, Fe, Mn, and Zn. The percentage of an element extracted varied dramatically with the element, procedure and mineral. Relatively little Si was extracted from the clays by the procedures employed, but Al extraction varied from 0 to 66% of the Al present. Fe extraction varied from .2 to 69%, Mn extraction from 0 to 100%, and Zn extraction from .5 to 69%. The high percentage of Al extracted by acid and acid‐peroxide treatment suggests that considerable destruction of the clay mineral structure had occurred. Clay structure disruption was also indicated by changes in the peak height/ width ratio before and after sample treatment. The relatively large amounts of trace metals extracted by pyrophosphate solution, without influencing the x‐ray diffraction patterns for the minerals, suggest that environmental scientists should consider this method as a means of trace element extraction.

Key words:

• Trace elements
• clay minerals
• chemical extractions