1. For the formic acid reduction method, see potassium iodide, the difference is that arsenic and heavy metal removal agents are added for solution purification. Iron filings reduction method Add 100% to 103% of the theoretical amount of caustic potash to a reactor filled with distilled water, add a certain amount of iodine in stages under stirring, and keep stirring at 80 to 90 °C for about 1 hour. The reaction solution is brown. When the Ph value is 6 to 7, potassium iodate crystals appear. The reaction solution was cooled to below 30°C, and iron filings were added to reduce potassium iodate to potassium iodide. The reaction starts violently. After the reaction is moderated, heat and boil, continue to stir the reaction for 1 to 2 hours, then adjust the Ph value to 8 with 10% caustic potash solution, add arsenic remover and heavy metal remover to purify the solution, stand, filter, remove Arsenic and heavy metals and other impurities, the filtrate is evaporated and concentrated to precipitate crystals, and then crystallized by cooling, centrifuged, and dried to obtain the finished product of edible Potassium Iodide Solution, which is 3I2+6KOH→5KI+K1O3+3H2OKIO3+3Fe+3H2O→KI+3Fe(OH) 2
2. At present, Potassium Iodide Solution is mostly produced by the formic acid reduction method in China. That is, Potassium Iodide Solution and potassium iodate are generated by the action of iodine and potassium hydroxide, and then potassium iodate is obtained by reducing Potassium Iodide Solution with formic acid or charcoal. However, iodate is generated in this method, and the product should not be used as a food additive. Food grade Potassium Iodide Solution can be produced by the iron filing method. The iron filing method uses iodine and iron filings as raw materials. A part of iron filings was placed in the reactor, 7 parts (mass) of water was added, and 3.3 parts of iodine was added in batches at 65~cT (high temperature iodine is easy to sublime). After adding iodine tablets, the solution is dark reddish-brown, and the second batch of iodine tablets can be added only after the solution is light green. Then the iron filings are filtered off to obtain a ferrous iodide solution, which is added to a 10:3 (mass) potassium carbonate aqueous solution to generate iron carbonate precipitation and Potassium Iodide Solution. The solution is allowed to stand, and the supernatant liquid is precipitated after clarification, heated and concentrated to a relative density of 1.75-1.81 and then filtered; when the filtrate continues to evaporate to a relative density of 1.93-1.98, it is filtered while hot. Cool to 60～70℃ and stand for crystallization, and after separation, dry at 70～90℃ to obtain anhydrous Potassium Iodide Solution product. Fe+I2→FeI2FeI2+K2CO3—2KI+FeCO3↓
