Precipitation from high-level liquid

Kondo, Y and Kuboto, M., Precipitation Behavior of Platinum Group Metals from Simulated High Level Liquid Waste in Sequential Denitration Process, J. Nucl. Sci. Technol., 29(2), (1992), ppl40-l48. 

High-Level Liquid Waste (HLLW) Treatment. The high-level liquid waste is produced as a raffinate from the HA solvent extraction cycle in Purex. After generation, the HLLW is immediately transferred to the WTF via an underground pipeline without concentration or interim storage. This strategy minimizes the problems associated with solids precipitation. 

The environmental impact of hormones seems to be mainly related to liquid effluents. However, in the light of the high levels of hormones present in solid matrices such as manure or sludge from WWTP with poor hormone removal rates (e.g. enhanced precipitation [116]) there, it is still a need to implement treatment processes to efficiently remove hormones from sludge and manure. 

Precipitation from substance Initiator Polymer Monomer is reaction medium, see third column So in M D in M PVC, PAN from liquid LDPE or LDPE made from gaseous monomer Powder Polymerization, is possible. LDPE is precipitated from the Separation of the polymer ethylene gas by means of high-from the reaction medium pressure polymerization. PAN causes no problems, even at is nonmeltable, is dissolved in high molar mass levels. dimethyl formamide and spun into threads... 

As an example, most of the radioactivity from plutonium production is found in the liquid high-level waste from the first cycle of the Purex process. This liquid is neutralized with sodium hydroxide and stored in earth-shielded tanks. There a sludge settles out that contains most of the radioactivity. The residual liquor is partially evaporated to decrease the volume of the waste, and sodium nitrite crystallizes on top of the sludge. In a process to be used at the Savannah River plant, the sodium liquor fraction, containing most of the cesium fission product, is pumped from the tank and precipitated with tetra-phenyl borate. The precipitate will be calcined and packaged for disposal in a high-level repository, and the sodium nitrate crystallized from the residual liquor and sent to a low-level waste repository. 

The usual means of identifying and quantifying the level of these additives in polymer samples is performed by dissolution of the polymer in a solvent, followed by precipitation of the material. The additives in turn remain in the Supernatant liquid. The different solubilites of the additives, high reactivity, low stability, low concentrations and possible co-precipitation with the polymer may pose problems and lead to inconclusive results. Another sample pretreatment method is the use of Soxhlet extraction and reconcentration before analysis, although this method is very time consuming, and is still limited by solubility dependence. Other approaches include the use of supercritical fluids to extract the additives from the polymer and Subsequent analysis of the extracts by microcolumn LC (2). 

Another point is related to the high acidity level of the final solution, which leads to certain limitations in the subsequent technological steps. Specifically, the high acidity of the initial solution eliminates any possibility for selective extraction, i.e. sequential separation of tantalum and then of niobium. Due to the high concentration of acids, only collective extraction (of tantalum and niobium together) can be performed, at least at the first step. In addition, extraction from a highly acidic solution might cause additional contamination of the final products with antimony and other related impurities. In order to reduce the level of contaminants in the initial solution, some special additives are applied prior to the liquid-liquid extraction. For instance, some mineral acids and base metals are added to the solution at certain temperatures to cause the precipitation of antimony [455 - 457]. 

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