Chlorine from seawater

Preparation and Manufacture. Magnesium chloride can be produced in large quantities from (/) camalhte or the end brines of the potash industry (see Potassium compounds) (2) magnesium hydroxide precipitated from seawater (7) by chlorination of magnesium oxide from various sources in the presence of carbon or carbonaceous materials and (4) as a by-product in the manufacture of titanium (see Titaniumand titanium alloys). 

Reaction with Other Halides. Bromide ion is oxidi2ed by chlorine to bromine. This is the basic reaction in the production of bromine from seawater, brines, or bitterns. 

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 ... 

Sullivan et al. [69] studied the loss of phthalic acid esters and chlorinated biphenyls from seawater whilst stored in glass containers. Equilibrium was essentially reached in 12 h at 25 °C. Labelled compounds were used in some of the studies. Table 1.10 shows that between 2.2 and 49.9% of the organic solutes were lost from the spiked solutions. 

Carlson and Weberg [ 12] have also studied the interference from iodate during the iodometic determination of residual chlorine in seawater. These workers confirmed that due to the presence of naturally occurring iodate, results from the iodometric determination carried out at pH 2 were up to 20% higher... 

Statham [448] has optimised a procedure based on chelation with ammonium dithiocarbamate and diethylammonium diethyldithiocarbamate for the preconcentration and separation of dissolved manganese from seawater prior to determination by graphite furnace atomic absorption spectrometry. Freon TF was chosen as solvent because it appears to be much less toxic than other commonly used chlorinated solvents, it is virtually odourless, has a very low solubility in seawater, gives a rapid and complete phase separation, and is readily purified. The concentrations of analyte in the back-extracts are determined by graphite furnace atomic absorption spectrometry. This procedure concentrates the trace metals in the seawater by a factor of 67.3. 

Harvey GR (1972) Absorption of chlorinated hydrocarbon from seawater by a crosslinked polymer, Woods Hole, MA, USA... 

In summary, the FT-30 membrane is a significant improvement in the art of thin-film-composite membranes, offering major improvements in flux, pH resistance, and chlorine resistance. Salt rejections consistent with single-pass production of potable water from seawater can be obtained and held under a wide variety of operating conditions (ph, temperature, pressure, and brine concentration). This membrane comes close to being the ideal membrane for seawater desalination in terms of productivity, chemical stability, and nonbiodegradability. 

Bromine (Br) is the most important genetic trace element for potash within salt deposits. Bromide minerals do not form during the crystallization of salts from seawater rather bromine tends to accumulate with increasing brine concentration and occurs only as a trace in solid solution as a substitute for chlorine in the precipitating chloride minerals. 

Bromine has an ionic radius of 1.96 A and thus easily substitutes for chlorine (1.81 A) in the halite crystal lattice as well as in the other chloride salts. The distribution coefficients for bromine in chloride salts deposited from seawater is less than 1 (Warren 2006). 

Harvey, G. R. Adsorption of Chlorinated Hydrocarbons from Seawater by a Crosslinked Polymer U.S. Environmental Protection Agency. U.S. Government Printing Office Washington, DC, 1973 EPA Report No. R2-73-177. 

The commercial production of bromine from salt-well brines or from seawater depends on the fact that chlorine is capable of displacing bromine from its salts. Bromine is extracted from seawater by a process involving the following steps ... 

In the process used by Norsk Hydro, magnesium hydroxide extracted from seawater with the aid of calcined dolomite is mixed with charcoal and magnesium chloride brine and is heated to 1000-1200°C in the presence of chlorine produced during subsequent electrolysis of magnesium chloride. The main reactions are [266]... 

Chlorine is applied in a number of forms from chlorine gas to hypochlorite solution. It is important that the source of chlorine is not contaminated. For example, chlorine gas has been found to be contaminated with carbon tetrachloride, hypochlorite that is stored for a long time gradually breaks down to give chlorate, and hypochlorite generated electrolytically from seawater or brine with a high bromide content can have high concentrations of bromate. 

According to the latest estimates of Skinner [18], elements potentially recoverable from seawater are sodium, potassium, magnesium, calcium, strontium, chlorine, bromine, boron, and phosphorus because of their practically unlimited presence in the ocean. After improving respective technologies, recovery of the following elements is expected to become profitable as well lithium, rubidium, uranium, vanadium, and molybdenum. Additional profit can be gained since desalinated water will probably be obtained as a by-product. This could be important for countries with a very limited number of freshwater sources (e.g., Israel, Saudi Arabia). 

Bromine is produced directly from seawater by the so-called airstripping technique [60, 2, p. 31]. The process involves acidifying seawater with H2SO4. Treatment with chlorine then oxidizes the bromides in the seawater to volatile elemental bromine. The bromine is removed from the solution in an airstream for reabsorption by different aqueous or organic... 

The solvents consisted of artificial seawater of two compositions, with nearly identical salinities (35% ), chlorinities (19.1%o), and molalities of sodium and chloride ions see Table I). The composition was close to that selected by Lietzke et at 14). Sulfate was omitted from seawater I to avoid the complications of HS04 formation when strong acid was added. The ionic strength of the sulfate-free seawater was main-... 

Sodium chloride Sodium chloride is, as a starting material for the electrolytic production of chlorine and sodium hydroxide, available in unlimited quantities. It is either extracted from natural deposits (up to 70%) or from seawater. In the USA, the economically workable deposits of sodium chloride are estimated to be greater than 55 10 t and in the Federal Republic of Germany there is estimated to be 100 10 km of deposits. Extraction is either carried out by mining or leaching (i.e. dissolution of... 

Derivation From seawater and natural brines by oxidation of bromine salts with chlorine solar evaporation (Great Salt Lake) from salt beds at Stassfurt and the Dead Sea. 

Sodium chloride, or common salt, is one of the earliest chemical commodities produced. Its production from seawater was prompted by essential dietary needs, and later for its value as a food preservative caused by the scattered accessibility of land-based sources. The word salary itself is derived from the Roman salarium, which was a monetary payment given to soldiers for salt purchase to replace the original salt issue. While the initial production and harvesting of sodium chloride was from dietary interests, food needs today represent less than 3% of consumption, and uses as a chemical intermediate far exceed this (Table 6.1). The wide availability of sodium chloride has contributed to the derivation of nearly all compounds containing sodium or chlorine from this salt, and to the establishment of many large industrial chemical operations adjacent to major salt deposits. Three general methods are in common use for the recovery of sodium chloride, which in combination were employed for the worldwide production of 225 million tonnes of this commodity in 2000 and 183 million tonnes in 1990 (Table 6.2). 

Iodine is also prepared from seawater and natural brine by the oxidation of I ions with chlorine. Because Br and 1 ions are invariably present in the same source, they are both oxidized by chlorine. However, it is relatively easy to separate Br2 from... 

The preparation of molecular bromine and iodine from seawater by oxidation with chlorine was discussed in Section 4.4. In the laboratory, chlorine, bromine, and iodine can be prepared by heating the alkali halides (NaCl, KBr, or KI) in concentrated sulfuric acid in the presence of manganese(IV) oxide. A representative reaction is... 

Bromine is produced commercially from natural brines and from seawater either by electrolysis or with displacement by chlorine, a somewhat more reactive halogen. The concentration of bromine in seawater is approximately 67 parts per million (ppm) by weight it is found in Earth s crust at an average level of 3 ppm. 

Bromine is extracted from seawater by bubbling in chlorine gas which oxidises the Br" ions. 

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