Scheelite accounts for more than two-thirds of the total tungsten resource ( Dong et al., 2019). Wolframite and scheelite are the main tungsten resources with industrial application value in nature ( Bohlouli et al., 2016 Song et al., 2019 Zhang et al., 2019 Yadav et al., 2020 Liu et al., 2021). After phosphorus removal, the concentration of phosphorus in the ammonium tungstate solution was below 10 ppm, which meant deep phosphorus removal was achieved. The phosphorus removal efficiency was above 99% and tungsten loss was less than 0.22% under the following conditions: the basic magnesium carbonate stoichiometric ratio was 1.5, the initial phosphorus concentration was ranging from 0.5 to 4 g/L, the reaction time was 120 min and temperature was 25☌. Then, the small portion of phosphorus remaining in the ammonium tungstate solution was further deeply removed by basic magnesium carbonate percipitation. Results showed that the crystallization ratio of phosphorus was above 95% under the conditions of an ammonia concentration of 4.18 mol/L, an initial phosphorus concentration ranging from 15 g/L to 30 g/L, a holding time of 60 min and the temperature of 20☌. First, ammonium phosphate was crystallized and separated from the ammonium tungstate solution by blowing ammonia and cooling. In this study, a novel process for ammonium phosphate recovery and deep phosphorus removal from the solution was proposed. For production of qualified ammonium paratungstate products, phosphorus must be deeply removed from the ammonium tungstate solution. The ammonium tungstate solution obtained by leaching scheelite with phosphate contains a large amount of phosphorus. Faculty of Materials Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou, China.5,(1976).Liang Yang, Jie Qu, Dandan Gong, Zhongbing Wang, Ruixiang Wang* and Linsheng Wan* Pitzer, Ion Interaction Approach: Theory and Data Correlation, Chap. (The Chemical Rubber Co., Cleveland, OH, 1972).ĭ.
Weast, Handbook of Chemistry and Physics, 53rd edn. PNWD-SA-4436 (Pacific Northwest National Laboratory, Richland, WA, 1997). Pitzer, Thermodynamic Analysis of Aqueous Solutions Using INSIGHT. Martell, Stability Constants of Metal-Ion Complexes. WHC-MR0132 (Westinghouse Hanford Company, Richland, WA, 1990).ĭ. Anderson, A History of the 200 Area Tank Farms. HNF-SD-WM-TI-740 (Lockheed Martin Hanford Company, Richland, WA, 1998). Schultz, Standard Inventories of Chemicals and Radionuclides in Hanford Site Tanks. PNL-8288 (Pacific Northwest National Laboratory, Richland, WA, 1993). 2: Detailed Description of First Example Flowsheet. Swanson, Clean Option: An Alternative Strategy for Hanford Tank Waste Remediation. The log K o values of reactions involving these species were found to be 2.78☐.3, 3.48☐.3, and 1.97☐.3, respectively. Contrary to the data recently reported in the literature, (1) only a limited number of aqueous species with up to about four orders of magnitude lower values for the formation constants of these species are required to explain Cr(III)-phosphate reactions in a wide range of pH and phosphate concentrations. A combination of techniques (XRD, XANES, EXAFS, Raman spectroscopy, total chemical composition, and thermodynamic analyses of solubility data) was used to characterize solid and aqueous species. Extensive studies on the solubility of amorphous Cr(III) solids in a wide range of pH (2.8–14) and phosphate concentrations (10 −4 to 1.0 m) at room temperature (22☒)☌ were carried out to obtain reliable thermodynamic data for important Cr(III)-phosphate reactions. Chromium(III)-phosphate reactions are expected to be important in managing high-level radioactive wastes stored in tanks at many DOE sites.
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