Iodide brines

Muramatsu Y., Fehn U., and Yoshida S. (2001) Recycling of iodide in fore-arc areas evidence from the iodide brines in Chiba, Japan. Earth Planet. Sci. Lett. 192, 583-593. 

Gr. iodes, violet) Discovered by Courtois in 1811, Iodine, a halogen, occurs sparingly in the form of iodides in sea water from which it is assimilated by seaweeds, in Chilean saltpeter and nitrate-bearing earth, known as caliche in brines from old sea deposits, and in brackish waters from oil and salt wells. 

Brines. About 65% of the iodine consumed in the world comes from brines processed in Japan, the United States, and the former Soviet Union (see Chemicals frombrine). The predorninant production process for iodine from brines is the blow-out process, which was first used in Japan. Iodine is present in brines as iodide, and its concentration varies from about 10 to 150 ppm. As shown in Figure 3, the recovery process can be divided into brine clean-up, iodide oxidation to iodine followed by air blowing out and recovery, and iodine finishing. 

The clarified and acidified brine is treated with gaseous chlorine which is injected into the solution in a small excess over the theoretical stoichometric relation by weight of 0.28 1 chlorine to iodide. The oxidation occurs according to... 

The I2 formed stays in solution, exerting a certain vapor pressure, and is extracted from the brine in a countercurrent air blow-out process. The extracted brine leaves the extraction tower and is discarded or reinjected into the wells to avoid sinking of the soil. The iodine-loaded air is then submitted to a cocurrent desorption process by means of an acidic iodide solution to which SO2 is added. By this solution the iodine is reduced to iodide by the following reaction ... 

Part of the continuously recirculated solution is bled off and sent to the iodine finishing process. Iodine finishing consists of contacting this bleed of concentrated acidic iodide solution with gaseous chlorine, through which iodine is formed by oxidation and precipitated. After iodine precipitation, the resulting acidic mother Hquor, saturated with free iodine, is pumped back to acidify the clarified brine and to recover the remaining iodine. 

For brines having very low iodide concentrations, ie, in some facilities in Japan and in the former USSR, the activated carbon method of recovery is used. This method consists of a process involving the treating of the acidified brine with sodium nitrite in large tanks, where the following reaction takes place ... 

Typical brines received at an Arkansas bromine plant have 3—5 g/L bromide, 200—250 g/L chloride, 0.15—0.20 g/L ammonia, 0.1—0.3 g/L hydrogen sulfide, 0.01—0.02 g/L iodide, and additionally may contain some dissolved organics, including natural gas and cmde oil. The bromide-containing brine is first treated to remove natural gas, cmde oil, and hydrogen sulfide prior to introduction into the contact tower (48). 

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. 

A degassed suspension of lhe halo compound 14 and an alkyne (1.2 equiv) in Et3N (0.1-0.2 mol) was stirred in the presence of dichlorobis(triphenylphosphane)palladium(II) (0.02 equiv) and coppcr(I) iodide (0.04 equiv) at 20 C for 20 h. EtOAc was added and the mixture was washed with H20 and brine the organic phase was dried (MgSOi) and evaporated to yield the product. 

Iodine occurs as iodide ions in brines and as an impurity in Chile saltpeter. It was once obtained from seaweed, which contains high concentrations accumulated from seawater 2000 kg of seaweed produce about 1 kg of iodine. The best modern source is the brine from oil wells the oil itself was produced by the decay of marine organisms that had accumulated the iodine while they were alive. Elemental iodine is produced by oxidation with chlorine ... 

Walters [24] examined the effect of chloride on the use of bromide and iodide solid state membrane electrodes, and he calculated selectivity constants. Multiple linear regression analysis was used to determine the concentrations of bromide, fluorine, and iodide in geothermal brines, and indicated high interferences at high salt concentrations. The standard curve method was preferred to the multiple standard addition method because of ... 

Buchberger et al. [104] carried out a selective determination of iodide in brine. The performance of a potentiometric method using an ion-selective electrode and of liquid chromatography coupled with ultraviolet detection at 230 nm were compared as methods for the determination of iodide in the presence of other iodide species. Satisfactory results were obtained from the potentiometric method provided the solution was first diluted tenfold with 5 M sodium nitrate, and external standards were used. Better reproducibility was, however, achieved with HPLC, provided precautions were taken to prevent reduction of iodine to iodide in the mobile phase, for which extraction of iodine with carbon tetrachloride prior to analysis was recommended. This was the pre-... 

Acetanilide (13.5 g), (substituted) aromatic bromide (25 g), potassium carbonate (13.2 g), and copper iodide (1.9 g) were heated (190°C) and stirred overnight. After cooling to room temperature toluene was added and the precipitate filtered. The solution was concentrated and the excess of bromide removed by distillation under reduced pressure. The residue was dissolved in ethanol (200 mL), potassium hydroxide (10.3 g) was added, and the mixture refluxed overnight. Ethanol was evaporated, the residue dissolved in dichloromethane, and washed with brine. The organic layer was dried over MgS04 and concentrated to obtain the crude diphenylamine. 

Process to Remove Sulphate, Iodide and Silica from Brine... 

This chapter introduces applications of RNDS to the removal of sulphate, iodide and silica from brine. 

In the brine system, iodide is mixed with raw salt. It precipitates in membranes in the electrolysis process causing the loss of current efficiency in the membrane. Synergy effects in combination with other impurities have been reported [7, 8]. 

Iodide is oxidised to iodate or periodate in the membrane cell during the electrolysis process. Iodide, iodate and periodate are therefore present in the brine of a membrane electrolyser. Figure 12.5 shows comparative plots of laboratory adsorption test data for the removal of iodide and other relevant species. 

Ion-exchange resin, containing zirconium hydroxide, is packed into the column to which brine containing iodide is supplied from the top. The observed sequence by rate of removal is iodide ion [Pg.171]

In order to remove effectively iodide by RNDS , oxidation of iodide to iodate or periodate is necessary. Iodide is oxidised to iodate with excess chlorine. Through contact of dechlorinated brine with the ion-exchange resin containing zirconium hydroxide, the iodide is therefore removed from the brine. 

In the case of well brine, the anolyte is not circulated as the iodide content is too high. In this situation, a portion of the anolyte containing chlorine is added to the well brine and after oxidising the iodide to iodate the brine is sent to the RNDS . 

In the brine electrolysis system, silica is also contained in raw salt. Silica will precipitate on to membranes in the presence of calcium, strontium, aluminium and iodine resulting in the loss of current efficiency [8-10]. Silica can also be removed in a column filled with ion-exchange resin containing zirconium hydroxide, just like the iodide ion. 

As was mentioned previously, an effective system, RNDS , has been developed to remove particular impurities from brine used in membrane electrolysis procedures. The basic concept of RNDS is to bring the feed brine into contact with an ion-exchange resin containing zirconium hydroxide for the adsorptive removal of impurities. For the removal of the sulphate ion from brine, commercial plants utilising RNDS are already in service. For the elimination of iodide and silica, pilot-scale testing is being planned. 

In the silver nitrate precipitation process, iodide in the brine is precipitated as silver iodide. The iodide is treated with iron to yield ferrous iodide. Passing chlorine through the ferrous iodide solution liberates iodine. 

In the ion-exchange method, brine solution is passed through an anion-exchange resin. Iodide (and polyiodide) anions from the solution adsorb onto the resin from which they are desorbed by treatment with caustic soda solution. The resin is treated with sodium chloride solution to regenerate its activity for reuse. The iodide solution (also rich in iodate, IO3 ions) is acidified with sulfuric acid. The acid solution is oxidized to precipitate out iodine. Iodine is purified by sublimation. 

Methylamine occurs in herring brine 2 in crude methyl alcohol from wood distillation,3 and in the products obtained by the dry distillation of beet molasses residues.4 It has been prepared synthetically by the action of alkali on methyl cyanate or iso-cyanurate 5 by the action of ammonia on methyl iodide,6 methyl chloride,7 methyl nitrate,8 or dimethyl sulfate 9 by the action of methyl alcohol on ammonium chloride,10 on the addition compound between zinc chloride and ammonia,11 or on phos-pham 12 by the action of bromine and alkali on acetamide 13 by the action of sodamide on methyl iodide 14 by the reduction of chloropicrin,15 of hydrocyanic or of ferrocyanic acid,16 of hexamethylenetetramine,17 of nitromethane,18 or of methyl nitrite 19 by the action of formaldehyde on ammonium chloride.20... 

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