Coprecipitation process operation

The emulsion liquid membrane (ELM) process was shown to be an effective method for pre-concentrating dilute selenium streams, such as those found in the wastewaters from petroleum refineries. By concentrating the selenium, the ELM process can greatly reduce the operating costs and capital costs of the coagulation/coprecipitation processes presently used to remove selenium. 

Fig. 1. Schematic flowsheet of uranium processing (acid leach and ion exchange) operation. Numbers refer to the numbers that appear in the boxes on the flowsheet. Operations (3), (6), (9), and (11) may be done by thickening or filtration. Most often, thickeners are used, followed by filters. The pH of the leach slurry <4) is elevated to reduce its corrosive effect and to improve the ion-exchange operation on the uranium liquor subsequently separated, In tile ion exchange operation (7), resin contained in closed columns is alternately loaded with uranium and then eluted. The resin adsorbs the complex anions, such as UC fSO 4-. in which the uranium is present in the leach solution. Ammonium nitrate is nsed for elution, obtained by recycling the uranium filtrate liquor after pH adjustment. Iron adsoibed with the uranium is eluted with it. Iron separation operation (8) is needed inasmuch as the iron hydroxide slurry is heavily contaminated with calcium sulfate and coprecipitated uranium salts. Therefore, the slurry is recycled to the watering stage (3). Washed solids from 1,6). the waste barren liquor from (7), and the uranium filtrate from (11) are combined. The pH is elevated to 7.5 by adding lime slurry before the mixture is pumped to the tailings disposal area. (Rio Algom Mines Limited, Toronto)...

There are several ways to carry out the precipitation process (Fig. 3) [14]. The simplest implementation of the precipitation reaction is the batch operation where the solution from which the salt is to be precipitated is usually present in the precipitation vessel and the precipitating agent is added. The advantage of this mode of operation is the simple way in which the product can be obtained the most severe disadvantage is the variation of batch composition during the precipitation process. This can lead to differences between the product formed during the initial stages of the precipitation and the precipitate formed at the end of the process. If a coprecipitation is carried out this way, it is important to decide which compounds are present in the vessel and which compounds are to be added. If the pre-... 

In the first separation procedure operated in a technical scale, was separated as Pu(IV) from U and fission products by coprecipitation with BiP04 (bismuth phosphate process). Today, solvent extraction is applied, because it leads to higher decontamination factors and can be operated as a continuous process. 

Seaborg and associates [LI] had found that tetravalent plutonium [Pu(IV)] could be coprecipitated from aqueous solution in good yield with insoluble bismuth phosphate BiP04, made by adding bismuth nitrate and sodium phosphate to an aqueous solution of plutonium nitrate. The bismuth phosphate process was developed at the Metallurgical Laboratory, demonstrated at the X-10 pilot plant at Oak Ridge National Laboratory in 1944, and put into operation for large-scale recovery of plutonium from irradiated fuel at Hanford in early 1945. 

Molybdate-Based Catalysts. The first catalyst commercialized by SOHIO for the propylene ammoxidation process was bismuth phosphomolybdate, Bi9PMoi2052, supported on silica (9). The catalytically active and selective component of the catalyst is bismuth molybdate. In commercial fluid-bed operation, the bismuth molybdate catalyst is supported on silica to provide hardness and attrition resistance in the fluidizing environment. Bismuth molybdate catalysts can be prepared by a coprecipitation procedure using aqueous solutions of bismuth nitrate and ammonium molybdate (10). The catal3ret is produced by drying the precipitate and heat treating the dried particles to crystallize the bismuth molybdate phase. Heat treatment temperature for bismuth molybdate catalysts is generally arovmd 500°C. 

Fig. 10.2 Schematic of MBP process. MBP process is comprised of several unit operations including stock solution preparation, controlled coprecipitation, filtration, washing cycles, isolation of...

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