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IN-VITRO FORMATION OF PYROMORPHITE VIA REACTION OF PB SOURCES WITH SOFT-DRINK PHOSPHORIC ACID
Citation:
Scheckel*, K G. AND J A. Ryan*. IN-VITRO FORMATION OF PYROMORPHITE VIA REACTION OF PB SOURCES WITH SOFT-DRINK PHOSPHORIC ACID. Presented at American Society of Agronomy Annual Meeting, Charlotte, NC, 10/21-25/2001.
Description:
The risk of Pb adsorption into the body may be greatly diminished when accompanied by a phosphate sink. One of the most labile, albeit not healthiest, forms of phosphate consumed in the human diet is derived from cola soft drinks that use phosphoric acid as a preservative and also to promote a sharp, crisp taste. We investigated the formation of pyromorphite by the addition of Pb materials (PbCl2, Pb-contaminated paint, and Pb-contaminated soil) to cola soft drinks (regular, diet, and caffeine-free regular) containing phosphoric acid and observed a significantly reduced bioavailability of Pb. For example, an initial 1000 ppm PbCl2 solution concentration was reduced 97% within 5 minutes at a pH of 2.0 and further reduced to greater than 99.99% at the end of the 6 hour experiment (pH 7.0). The experiments were conducted as a two-phase system to represent stomach (pH 2.0, 1 hour) and gastrointestinal (pH 7.0, 5 hours) environments at body temperature (37C). The brand or type (regular, diet, or caffeine-free) had little influence on the formation of pyromorphite although each soft drink examined had differing concentrations of P. X-ray adsorption spectroscopy (XAS), X-ray diffraction (XRD), and high-resolution thermogravimetric analysis (HRTGA) were conducted to identify and characterize the formed pyromorphite.