THE STRUCTURE, SYNTHESIS, AND SOLID STATE CHEMISTRY OF DAWSONITE

A single crystal X-ray diffraction study of dawsonite confirmed that the structure consisted of Al(OH)(,2)CO(,3)('-) chains in which the aluminum atoms were connected by a combination of bridging OH('-) groups and bridging bidentate carbonate groups. Inter-chain bonding involved both sodium-oxygen and hydrogen bonding. An R-value of 0.059 was obtained.; A new method to synthesize dawsonite was devised utilizing the principle of homogeneous precipitation. Urea, dissolved in a sodium aluminate solution, decomposed upon heating to form carbon dioxide which led to precipitation of dawsonite. Dawsonite prepared in this fashion compared favorably to oil shale dawsonite when studied using a variety of physical and chemical methods.; Synthetic dawsonite was heated at discrete temperatures from 300-800(DEGREES)C for periods from 30 minutes to 22 hours and the nature of the resultant products investigated. Heating dawsonite at 300(DEGREES)C for 22 hours or at 350(DEGREES)C for 30 minutes led to decomposition. The initial solid decomposition products were sodium carbonate and a form of alumina. Subsequent hydrolysis experiments identified this alumina as rhoalumina. Water extracted nearly one-half of the aluminum from dawsonite heated at 350(DEGREES)C for 30 minutes. Heating at higher temperatures and/or for longer times resulted in increases in the amount of water-soluble aluminum and the percent weight loss. The increases were attributed to the formation of non-crystalline sodium aluminate. Sodium aluminate crystallized upon heating dawsonite at 600(DEGREES)C for 30 minutes. Heating at 800(DEGREES)C for 30 minutes led to a 92 percent yield of sodium aluminate and 94 percent of the aluminum becoming water-soluble. Extraction experiments using 0.5M Na(,2)CO(,3) indicated that over ninety percent of the aluminum could be extracted from dawsonite heated at 350-800(DEGREES)C.; Similar heating and extraction experiments were conducted on a ten-percent dawsonitic oil shale sample. Water extracted nearly two-thirds of the acid-soluble aluminum from oil shale heated at 350(DEGREES)C for 30 minutes in air. Heating oil shale at temperatures above 600(DEGREES)C led to a decline in water-soluble aluminum until only seven percent could be extracted from oil shale heated at 800(DEGREES)C. Base extracted about 100 percent of the aluminum from oil shale heated at 350-650(DEGREES)C. Heating oil shale at 700-800(DEGREES)C led to progressively lower amounts of extractable aluminum.; The solubility reductions were due to interactions between dawsonite's thermal decomposition products and the other components of oil shale. In addition, iron dolomite was found to decompose at about 450(DEGREES)C to form calcite, periclase and maghemite. At 600(DEGREES)C, X-ray peaks due to Na(,2)Ca(,2)Si(,3)O(,9) were found while at 750(DEGREES)C, additional compounds such as forsterite, diopside and gehlenite were detected in the spent shale. The presence of gehlenite, Ca(,2)Al(,2)SiO(,7), explained the aluminum solubility decrease.; Oil shale heated in different atmospheres exhibited different aluminum extraction and X-ray diffraction patterns. If oil shale was heated in nitrogen, a residual carbon char remained inhibiting solid state reactions and keeping aluminum solubility high. By heating in air, the char burned-off and the solid state reactions proceeded leading to lower aluminum recovery.