How to Obtain Iodine
Iodine is a rare element and far too reactive to ever be found in elemental form. The most important commercial source of iodine is caliche, which is primarily found in Chile. It also exists in seawater and is concentrated in some seaweeds. The following steps will show several methods of obtaining iodine.
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Instructions
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Obtain iodine from seaweed in small amounts. Certain seaweeds like Bongo kelp store sodium iodide (NaI). After the sodium iodide is extracted, it can be reacted with sulfuric acid (H2SO4) to produce hydrogen iodide (HI) with the following reaction: NaI + H2S04 -> HI + NaHSo4. More sulfuric acid can be added to hydrogen iodide to obtain iodine with this: 2HI + H2SO4 -> I2 + SO2 + 2H2O.
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Recover iodine from seawater. Sulfuric acid is added to the seawater to obtain a dilute iodine solution from the iodide salts as described in the previous step. The iodine is evaporated and blown into an absorbing tower where sulfur dioxide reduces the iodine. Chlorine is added to this solution to concentrate the iodine and the process is repeated until a purity of about 99 percent is achieved.
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Mine the ore caliche, which contains sodium iodate (NaIO3). React the sodium iodate with sodium hydrogensulfite (NaHO3S) to reduce the iodine. This is the most economical method.
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Obtain iodine of extremely high purity with potassium iodide (KI) and copper sulfate (CuSO4) using this reaction: 2KI + CuSO4 -> K2SO4 + CuI2. The CuI2 immediately breaks down with this reaction: 2CuI2 -> 2CuI + I2. Copper iodide is insoluble so the pure iodine is easily recovered.
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