Effect of pH and temperature on the carbonate promoted dissolution of sodium meta-autunite

Release of uranium from Na-autunite, an artificial mineral created as a result of polyphosphate injection in the subsurface at the DOE Hanford Site, takes place during slow dissolution of the mineral structure. Stability information of the uranyl-phosphate phases is limited to conditions involving pH, temperature, and a few aqueous organic materials. The carbonate ion, which creates very strong complexes with uranium, is the predominant ion in the groundwater composition. The polyphosphate technology with the formation of autunite was identified as the most feasible remediation strategy to sequester uranium in contaminated groundwater and soil in situ. The objectives of the experimental work were (i) to quantify the effect of bicarbonate on the stability of synthetic sodium meta-autunite created as a result of uranium stabilization through polyphosphate injection, (ii) calculate the kinetic rate law parameters of the uranium release from Na-autunite during dissolution, and (iii) to compare the process parameters with those obtained for natural calcium meta-autunite. Experiments were conducted using SPTF apparatus, which consists of syringe pumps for controlling flow rate, Teflon reactors and a heating/cooling system. 0.25 grams of synthetic Na-autunite was placed in the reactor and buffer solutions with varying bicarbonate concentrations (0.0005 to 0.003 M) at different pH (6 - 11) were pumped through the reactors. Experiments were conducted at four different temperatures in the range of 5 - 60oC. It was concluded that the rate of release of uranium from synthetic Na-autunite is directly correlated to the bicarbonate concentration. The rate of release of uranium increased from 1.90 x 10-12 at pH 6 to 2.64 x 10-10 (mol m-2 s-1) at pH 11 at 23oC over the bicarbonate concentration range tested. The activation energy values were invariant with the change in the bicarbonate concentration; however, pH is shown to influence the activation energy values. Uranyl hydroxides and uranyl carbonates complexes helped accelerate the dissolution of autunite mineral.

Dean of the school board: An oral history of the distinguished career of G. Holmes Braddock

Effective school board leadership is often an ephemeral ideal in today's highly politicized public education arena. However, effective leadership is necessary in order to ensure a fair and equitable education for all students. This dissertation described and explained one school board member's perspective of his career as a lens from which to view and assess public educational policy making in Miami-Dade County. ^ Now retired after thirty-eight years of service, G. Holmes Braddock is the longest serving, contemporary, urban school board member in the country. Spanning nearly four decades, his perspective provides a comprehensive view of urban education both locally and nationally. The significance of his longevity and the impact of his leadership on educational policy-making was the focus of indepth interviews with Mr. Braddock and other key educational “influentials.” From this transcript data, recurring themes were revealed and categorized. Five elements of his perspective, i.e., teacher professionalization; desegregation; athletics; bilingual education; and his comprehensive leadership role, were identified and analyzed, as were five variables of his perspective, i.e., fairness; integrity; honesty; courage; and the situational context. Other secondary source material, such as excerpts from newspaper articles, school board minutes, and items from Mr. Braddock's own personal effects further augmented and triangulated the data. ^ Given that the purpose of this study was to describe and explain Mr. Braddock's perspective of his school board career, the findings can be understood from two different viewpoints. The elements of Mr. Braddock's perspective describe or characterize his career and represent the significant policy issues in which he demonstrated exceptional vision and leadership. However, taken alone, these elements cannot fully explain his distinguished career. Rather, an analysis of the variables of Mr. Braddock's perspective provides an explanation for the effectiveness of his leadership role. Personality traits such as fairness, integrity, honesty and courage and the impact of the situational context were factors that strongly influenced Mr. Braddock's decision-making. Thus, Mr. Braddock's school board career can be holistically understood as the intersection of person, place and time with significant public education policy issues. ^ The results of this study provide a unique and historical perspective of school board politics in Miami-Dade County. From Mr. Braddock's perspective, we are able to view one individual's leadership role over time and its impact on local public education policy. ^

Synthesis and characterization of photochromic indolyl substituted fulgides and fulgimides

The fulgide and fulgimide family constitutes an important class of organic photochromic compounds. The ability of fulgides and fulgimides to interconvert between two key forms by irradiation of different wavelength of light has made them promising material in optical memory devices, optical switches and sensors, and specialty dyes and inks. Thermal stability and hydrolytic stability of fulgides and fulgimides are essential for their practical applications. A deuterated trifluoromethyl indolylfulgide was synthesized based on the synthetic pathway of the proteo trifluoromethyl indolylfulgide using commercially available deuterated starting materials. Deuteration of the isopropylidene group improved the thermal stability of the indolylfulgide by a factor of 7. ^ Fulgimides are the most important fulgide derivatives. Fulgimides improve the hydrolytic stability of fulgides by replacing the succinic anhydride ring with a succinimide ring. A novel trifluoromethyl N-ethoxycarbonylmethyl indolylfulgimide was synthesized from trifluoromethyl indolylfulgide. The trifluoromethyl indolylfulgide was synthesized on a large scale in five steps with an overall yield of 18%. The indolylfulgide was then converted to indolylfulgimide by aminolysis follow by dehydration. The N-ethoxycarbonylmethyl indolylfulgimide showed enhanced hydrolytic stability and photochemical stability in 70/30 ethanol/water. ^ Three novel aqueous soluble fulgimides, trifluoromethyl carboxylic acid indolylfulgimide, dicarboxylic acid indolylfulgimide, and H-carboxylic acid indolylfulgimide, were synthesized. In sodium phosphate buffer (pH 7.4) at 37 ºC, an unusual hydrolysis of the trifluoromethyl group of the closed form of the carboxylic acid indolylfulgimide resulted in the dicarboxylic acid indolylfulgimide which has an additional carboxylic acid group. The closed form of dicarboxylic acid indolylfulgimide was further decarboxylated to generate H-carboxylic acid indolylfulgimide which was not photochromic. The trifluoromethyl dicarboxylic acid indolylfulgimide is the most robust fulgimide yet reported in aqueous solution. ^ A novel aqueous soluble methyl carboxylic acid indolylfulgimide was synthesized from methyl indolylfulgide. The methyl indolylfulgide was synthesized in five steps with an overall yield of 21%. The methyl carboxylic acid indolylfulgimide was synthesized by aminolysis follow by dehydration. The methyl carboxylic acid indolylfulgimide is expected to have improved thermal and photochemical stability in aqueous solutions relative to the trifluoromethyl analog.^