## LSU Historical Dissertations and Theses

1998

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Chemistry

#### First Advisor

Steven F. Watkins

#### Abstract

Two quantitative X-ray powder diffraction methods were used to analyze Phosphogypsum, a currently underutilized solid by-product of phosphoric acid production. Three kinds of synthetic mixtures were prepared to reflect the variable composition of phosphogypsum: AG (anhydrite and gypsum), QCD (quartz, calcite, and dolomite), and AGQCD. Compositions derived from the Whole Pattern fitting method for the binary and ternary mixtures agreed reasonably well with known values, with residuals $\rm\langle R\sp2\rangle = 0.10$ for eleven AG samples, and $\rm\langle R\sp2\rangle = 0.018$ for thirteen QCD samples. However, in the five-component mixtures, overlap of anhydrite, dolomite and gypsum peaks prevented quantitation. Compositions derived from the Matrix Flushing method were generally superior, with $\rm\langle R\sp2\rangle = 0.009$ for eleven AG mixtures, $\rm\langle R\sp2\rangle = 0.0004$ for thirteen QCD mixtures, and $\rm\langle R\sp2\rangle = 0.0197$ for nine AGQCD mixtures. The most notable exception in the determination of AG mixtures with 0-10% gypsum. The measured compositions were distorted in favor of gypsum, apparently due to the affinity of gypsum for water. Two single crystal structures, one organometallic and the other inorganic, were determined. $\rm\lbrack (phen)\sb2Cu\rbrack \sp{+}(hfacac)\sp{-}$ crystallizes in triclinic space group P1 with: a = 10.284(0)A, b = 11.685(0)A, c = 12.519(0)A and $\rm\alpha = 114.97(0)\sp\circ ,\ \beta = 90.77(0)\sp\circ ,\ \chi = 105.78(0)\sp\circ .\ Ba\sb{1-x}K\sb{x}BiO\sb3,\ x = 0.419(0),$ a superconductor with $\rm Tc = 29.5\sp\circ K.$ It crystallizes in cubic space group with Pm3m symmetry and a cell constant of a = 4.2948(0)A. The diffraction-quality crystal of $\rm Ba\sb{1-x}K\sb{x}BiO\sb3$ was synthesized by electrosynthesis in a molten KOH flux at $\rm 225\sp\circ C.$ The synthesis required ultra-pure KOH (99.99%), $\rm Ba(OH)\sb2{\cdot}8H\sb2O$ (99.8%), $\rm Bi\sb2O\sb3$ (99.9998%), and a cover gas of water-saturated ultra-pure Ar. The melt composition was based on weight ratios K/Ba = 17.2 and K/Bi = 12.5. The electrode deposition potential was 0.677 volts, starting current $\rm I\cong 20\ \mu A.$ Every attempt was made to maintain a current density of less than $\rm 0.5mA/cm\sp2,$ to ensure slow crystal growth.

9780591904710

193

COinS