Program
All Presentations (pdf)
Monday
8:15 Brent Means
10:10 James J. Gusek
12:40 Jonathan M. Dietz
2:15 Kimberly R. Weaver
4:00 Brent Means
Tuesday
8:45 Robert Kleinmann
9:15 Brent Means
9:30 James J. Gusek
10:00 Glenn C. Miller
10:30 Linda Ann Figueroa
12:40 Art Rose
1:10 Charles A. Cravotta III
1:40 Danielle M C Huminicki
2:50 Bernard Aube
3:20 Timothy K. Tsukamoto
3:50 Bradley R. Shultz
4:20 Kimberly R. Weaver
Wednesday
8:00 Linda Ann Figueroa
8:30 John Senko
9:00 Song Jin
10:10 Jonathan M. Dietz
10:40 Daryle H. Fish
12:40 John Chermak
1:10 Griff Wyatt
1:40 Dan Mueller
2:50 Sean C. Muller
3:20 Jack Adams
3:50 Roger Bason
3:50 Mark B. Carew
Thursday
8:00 Rep. John E. Peterson
8:30 Scott Sibley
9:00 Charles A. Cravotta III
9:30 Michael R. Silsbee
10:30 Lykourgos
Iordanidis
11:00 Mark Conedera
11:30 Barry Scheetz
1:25 William Benusa
1:55 Mike Sawayda
2:25 Susan J. Tewalt
3:25 Robert S. Hedin
3:55 Chad J. Penn
4:25 Ron Neufeld
Tuesday 1:40 Danielle M C Huminicki, Virginia Polytecnic Institute and State University
The Effect of Gypsum Coatings on Dissolution Rate of Calcite in AMD solutions
Author(s)
Danielle M C Huminicki
Virginia Polytecnic Institute and State
University
513 Hunt Club Road #28B
Blacksburg, VA 24060
(540) 443 1102
dhuminic@vt.edu
Dr. J Donald Rimstidt,
Virginia Polytecnic Institute and
State University
4044 Derring Hall
Blacksburg, VA 24061
(540) 392 8913
jdr02@vt.edu
Abstract
A common passive treatment for acid mine drainage (AMD) is to react it with limestone to neutralize its acidity and increase its net alkalinity. During treatment, secondary mineral coatings form on the limestone (armoring), which decreases its dissolution rate and reduces the effectiveness of this treatment. This research shows that gypsum can form epitaxially on calcite dissolving in sulfuric acid solutions by the coupled reaction CaCO3 (cal) + H2SO4 (aq) + 2H2O = CaSO4•2H2O (gyp) + H2CO3 (aq) An array of batch reactor experiments measured the dissolution rates of Iceland spar calcite (Asp = 0.015m2/g, 40-60 mesh fraction) at room temperature in 0, 0.1, 0.3, or 1.0 M solutions of sodium sulfate with pH values of 1.5, 2.0, 2.5, 3.0 or 3.5. Scanning electron microscopy (SEM) showed that gypsum coatings formed on calcite at low pH where sulfate concentrations were high. Rates of dissolution are reported in terms of moles of H+ consumed. The apparent rate, r', was calculated by numerical differentiation and the rate, r = r'/A (mol/m2sec). The general rate law selected as the best fit to the rate data was r = kt^-0.5. Calcite dissolution rates decline with time as the growing gypsum layer greatly reduces the rate of H+ transport to the calcite surface. This physical behavior can be derived from Fick’s first law of diffusion such that k = 1/2[DCA/f(gyp)porosityV]^0.5 for the rate law stated above.
Biography
Danielle M. C. Huminicki completed a B. Sc. (Hons.) degree in geology at the University of Manitoba in 2000 under the supervision of Dr. Frank Hawthorne on the crystal chemistry of beryllium minerals. Part of this work was published in a chapter in the Reviews in mineralogy and geochemistry series. Following her B.Sc., she continued to work on the crystal chemistry of phosphate minerals, which is also published in a reviews in mineralogy and geochemistry chapter. After receiving her M. Sc. degree in 2002 she began her Ph. D. at Virginia Tech with Dr. J. D. Rimstidt as her advisor. She is working on iron and sulfur mineralogy and geochemistry and the important kinetic processes associated with the treatment and prevention of acid mine drainage.