Chloride backwashing

The resin is backwashed with water to remove fines as well as the sodium chloride and sodium carbonate used to inhibit growth of bacteria and mold during storage. After backwashing, the resin remains covered with water and is then drained while methanol or acetone is... 

Junk et al. (5) found that the Rohm and Haas procedure (29) did not clean the resin sufficiently for use as an adsorbent for recovering nanogram-per-liter amounts of organic materials. Junk s resin preparation and cleaning procedure started with backwashing the resin with water to remove fines, sodium chloride, and sodium carbonate. 

A comparative study was conducted by cleaning XAD-2 resin by ultrasonic and Soxhlet extraction procedures. Two batches of XAD-2 resins from the same lot of uncleaned resin were cleaned by backwashing with water and then were subsequently extracted with methanol, acetonitrile, and methylene chloride. The solvent-to-resin volume ratio for both methods was 5 1. The volumes of wet resin for the Soxhlet extraction and the ultrasonic bath were 100 mL and 50 mL, respectively. The ultrasonic cleaning procedure was done in a Teflon-lined screw-cap amber jar (250 mL) for 1 h in each solvent. The Soxhlet extraction sequence was 24 h in methanol, 24 h in acetonitrile, and 48 h in methylene chloride. 

The presence of chloride, nitrate, sulfide, organic sulfonates, cyanates, organic amines, and particulate matters may interfere in the test. The two major interferences, chloride and nitrate, however, may be removed in the acid backwash steps. Sulfide reacts with methylene blue to form a colorless complex. Interference from sulfide may be removed by treating the sample with a few drops of 30% H2Oz, whereupon sulfide converted into sulfate. 

Amine Extraction. Tri-n-octylamine was prepared by repeated washing of tri-n-octylammonium chloride with IN NH4OH followed by washing with water. Uranium extraction experiments were performed with U-233 tracer which contained a small amount of hydrochloric acid. Successive backwashing of extracts with acetic acid was used to eliminate the chloride. Np-237 and Pu-239 were oxidized with ozone and back-washed two or three times to eliminate lower oxidation states. 

Backwashing of uranium from an amine solvent may be carried out by exchange of the uranyl sulphate anion with another anion, nitrate or chloride usually being employed, for example IN sodium chloride, 0 1N sulphuric acid solution, i.e. 

Fig. 4.28. Amex process for uranium. Stripping (Backwashing) agents (a) NasCOs sol n, e.g. 0-75M NasCOs (b) Chloride sol n, e.g. 1-OM NaCl-0 05M H2SO4 (c) Nitrate sol n, e.g. 0-9M NH4NO3-O IM HNOs (d) MgO slurry, e.g. 20 g MgO/1. (Brown, K.B. et al. Proc. 2nd U. N. Conf. on the Peaceful Uses of Atomic Energy, United Nations, New York, vol. 3.,...

Di (tridecyl) amine can also be used for the extraction of thorium from the very dilute liquor left after either ion-exchange or solvent extraction of Blind River ores. For example, in a two cycle process, tri-iso-octylamine first extracts the uranium and the di (tridecyl) amine cycle is then adjusted to remove the thorium with the minimum iron contamination. The thorium is backwashed with 1M sodium chloride-0 05M sulphuric acid solution and precipitated with ammonia. 

Although the solvent purification process is adequate for the production of say reactor-grade zirconium, it is possible to modify it so that pure hafnium may also be obtained. Distribution data are available for various solutions containing thiocyanate, sulphate and chloride from which it is possible, for example, to deduce that both hafnium and zirconium will extract into hexone provided the aqueous phase has a high thiocyanate concentration and a low chloride concentration. The zirconium may then be selectively backwashed in a second extractor using say an aqueous phase of high thiocyanate concentration and moderate sulphate concentration, where the separation factor of the system is high. The hafnium can then... 

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