Technology Research Of Removal Iodine In The Brine

Caustic soda is inextricably linked with our daily life and manufacture, are widely used in printing and dyeing, textile, metallurgical and other industries. And it is mainly made by the ionic membrane method in industrial production process, the brine is electrolyzed through divided into an anode chamber and a cathode chamber by ion exchange membrane, and the caustic soda is prepared according to the selection of ion exchange membrane. The service life of ion exchange membrane directly affects the yield and cost of production of caustic soda industry. The main factors is whether contains impurities in brine or not, such as: Ca2+, Sr2+, Ba2+, Al3+, Hg2+, Mg2+, Ni2+, Fe2+, Al3+, I-,SO42- ions, which will affect the current and voltage of electrolyzer and so on. The metal ions can be removed by precipitation method and chelating resins, sulfate ions can be removed through denitrification method. Relative to these ions, iodide is more difficult to be removed. If the brine contains iodide, the iodide will be oxidized to iodate and per-iodate form in the anode solution. The iodine will react with calcium ion, magnesium ion, sodium ion to forming insoluble, aggregated in ion exchange membrane. These reasons will seriously affect the service life of ion-exchange membrane. Therefore, it is very important to remove iodine from the salt water.This topic discusses the removal of iodine in the de-chlorination dilute brine, de-nitration brine, refined brine, and brine, which is used to product caustic soda by ion-exchange membrane method. Among them, there are (I-) in the brine, iodine ions and one or more other complicated forms of iodine the salt water. Designing the experiments to remove iodine, and analyzing of the results, the conclusions of research are as follows:1, The de-nitration brine, de-chlorination dilute brine and brine Iodine discussed in this topic all exist iodine ion, and have the other complicated forms of iodine, such as IO3-, I2, I3-, I2CI-, Cl2I- at the same time possibly.2, Improving the reported method by adding sodium sulfite as a reducing agent to remove iodine from the salt solution, adding overdose sodium sulfite, then adding oxidant, using the method of adsorbent to remove iodine. By optimizing of the amount of oxidant, the iodine removal rate of de-chlorination dilute brine, de-nitrification iodine and salt iodine can reach 29.41%,27.20%,30.13% respectively.3, Combining the adsorption of montmorillonite with copper salt precipitation method, modifying the montmorillonite with copper salt for iodine removal. Optimization of reaction conditions, under the condition of pH=5.0-6.0, reacting 2.00 g copper salts modified montmorillonite with 50 mL of saline, reaction time is 40 minutes. The adsorption rate of iodine in the de-nitrification, de-chlorination dilute brine and salt brine are 25.37%,27.10% and 24.90% respectively.4, the optimal conditions for the removal of iodine:the value of pH is 2.0; adding 0.40 mL oxidant in 100 mL brine; oxidation reaction for 40 minutes; the brine through the adsorption column at a flow rate of 6.0 mL/min. The most of iodine can be successfully removed, iodine removal rate reaches more than 80.00%, the content of iodine is less than 0.40 ppm, basically reached the standard of iodine content.5, The composition of de-chlorination dilute brine, de-nitrification brine and salt water is very complex with a lot of chlorine elemental which is in the same group with iodine. Moreover, existing form of iodine is also very complex, which may influences the extent of reactions. These reasons all can influence the removal effect of salt iodine.