Silver iodide, recovery

Recovery Process. In past years iodine was recovered at Long Beach, California from oil field brine and from natural brines near Shreveport, Louisiana (36,37). The silver process was used. Silver nitrate reacts with sodium iodide to precipitate silver iodide. Added iron forms ferrous iodide and free silver. The ferrous iodide then reacts with chlorine gas to release free iodine. After 1966, the silver process was replaced with the blowing-out process similar to the bromine process. 

Iodine, recovery of, from silver iodide residues, 2 6, 8 Iodine-131, purification of activity of carrier-free solutions of, 6 166... 

RECOVERY OF SILVER AND IODINE FROM SILVER IODIDE RESIDUES ... 

The residue containing silver iodide is freed from organic matter by extraction with a suitable solvent, dried, and ground to pass a 40-mesh sieve. The powdered residue is shaken with sufficient concentrated ammonia (sp. gr. 0.90) to dissolve all soluble silver salts. The suspension is filtered on a Bilchner funnel and the filtrate (I) is reserved for subsequent recovery of silver by reduction with sodium dithionite solution. 

The recovery of silver and iodine from silver iodide by this method is quantitative except for slight manipulative losses. 

Recovery of iodine from silver iodide residues, synthesis 3... 

In the procedure utilizing ion exchange, the sample solution was first subjected to the usual redox treatment to insure exchange, with the iodine ultimately being converted to iodide. The solution was then passed through a cation exchange resin of the phenol-sulfonic acid type and then iodide was adsorbed on preformed silver iodide. The recovery of radioiodine was greater than 97%. 

Matthews and Riley [99] preconcentrated iodide by co-precipitation with chloride ions. This is achieved by adding 0.23 g silver nitrate per 500 ml of seawater sample. Treatment of the precipitate with aqueous bromine and ultrasonic agitation promote recovery of iodide as iodate which is caused to react with excess iodide under acid conditions, yielding I3. This is determined either spectrophotometrically or by photometric titration with sodium thiosulfate. Photometric titration gave a recovery of 99.0 0.4% and a coefficient of variation of 0.4% compared with 98.5 0.6% and 0.8%, respectively, for the spectrophotometric procedure. 

The determination of iodide in milk (2% milkfat) by ion chromatography coupled with pulsed amperometric detection on a silver electrode is an application that benefits from matrix elimination of fats. The pulsed amperometric waveform improves reproducibility by electrochemically cleaning the working electrode on each pulse. In addition, the fats are removed from the sample using a disposable cartridge containing a polymeric reversed phase resin (OnGuard II RP, Dionex Corp.). When 50 jal of 0.1 mg/1 iodide was added to 200 jal of prepared milk, the recovery was 100%. The iodide peak area and retention time RSDs were 1.4% and 0.4% respectively [28]. 

Silver(II) fluoride, 3 176 Silver (I) iodide, residues of, recovery of silver and iodine from, 2 6 Silver(I) monofluorophosphate, 3 109... 

A number of methods were also developed for removing iodide impurities from acetic anhydride, such as syn-gas stripping [68], extraction in the presence of phenyl or alkyl phosphines [69], the use of lower fatty acids in combination with rhodium recovery [70], the use of silver-containing ion-exchangers [71], or oxidation with hydrogen peroxide [72]. 

Odink et al. (Odink et al., 1988) presented a simple method for the routine analysis of iodide in urine. Iodide was sep>arated by means of ion-pair reversed phase chromatography (RP-HPLC) and detected electrochemically with a silver electrode after a one-step sample cleanup. The coefficient of variation of a single analysis of iodide in a pooled urine sample (530 nmol/1) was 7.6%. The detection limit was 3 pmol (S/N 3), corresponding to 0.06 pmol/1. The recovery of iodide added to urine was 96 7 %. 

The commercial production of iodine depends on the source of the element. From natural brines, the process is similar to bromine recovery displacement of iodide ion (I ) by chlorine, blowout of the impure iodine, and repurification by sublimation. Other processes employ iodide precipitation by silver nitrate (AgNOs), separation on ion-exchange resins, or oxidation of iodide by sulfuric acid (somewhat similar to the original procedure used by Courtois). 

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