Removal of impurities from sodium chloride
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I would like to ask everyone: how can sodium carbonate and sodium bicarbonate be removed from sodium chloride? What is an appropriate pH level to maintain during this process? Are there any other control measures such as temperature and pressure?
Simply from the context of the question, adding hydrochloric acid causes sodium carbonate and sodium bicarbonate to react, producing sodium chloride as a byproduct.
Thank you, but this might be related to pH control. How can we maintain an appropriate pH level so that both sodium carbonate and sodium bicarbonate are completely converted into sodium chloride?
First, hydrochloric acid is added in an appropriate excess to cause sodium carbonate and sodium bicarbonate to react, producing sodium chloride, CO2, and H2O; the pH is maintained at 3–4, and air is passed to strip out the CO2 dissolved in the saline solution. Then, a small amount of sodium hydroxide solution is added to adjust the pH value to around 7–9, near neutral. If CO2 is not removed under slightly acidic conditions, the ionization equilibrium of the dissolved CO2 results in sodium carbonate and sodium bicarbonate levels in the brine always being in the range of several hundred milligrams per liter.