Monitoring the kinetics of metal surface precipitate formation using x-ray absorption fine structure (XAFS) spectroscopy

Conference · Tue Oct 01 04:00:00 EDT 1996

OSTI ID:370484

Scheidegger, A M; Sparks, D L ^[1]; Lamble, G M ^[2]

---

1. Univ. of Delaware, Newark, DE (United States)
2. Brookhaven National Lab., Upton, NY (United States)

Metal sorption on clay and oxide minerals is typically fast initially, then the rates gradually diminish. In the literature the decline in reaction rate has been attributed to metal sorption onto sites of lower reactivity, diffusion of the adsorbate into the adsorbent or by a precipitation reaction. Unfortunately, the above hypotheses were normally based solely on macroscopic studies. We investigated the effect of reaction time on the surface coordination environment of Ni sorbed onto pyrophyllite using X-ray absorption fine structure (XAFS) spectroscopy. The kinetics was studied over a long reaction period (minutes to months) and changes in the XAFS spectra were monitored. As reaction time progresses, surface precipitates increasing in size were depicted. This finding implies that slow nucleation processes cause the slow sorption kinetics. This study also emphasizes the importance of coupling kinetic studies with in-situ spectroscopic investigation in elucidating sorption mechanisms of metal ions onto mineral surfaces.

• OSTI ID: 370484
• Report Number(s): CONF-960376--
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
FINE STRUCTURE
MINERALS
NICKEL
OXIDE MINERALS
PRECIPITATION
PYROPHYLLITE
SORPTION
SORPTIVE PROPERTIES