How to separate sulfuric anhydride from a solution containing sodium sulfate, sulfuric acid, and sodium carbonate,

First, the solution is concentrated to a total concentration of 30% using multi-effect evaporation; after cooling, CO2 is introduced to convert sodium carbonate into sodium bicarbonate. Then, a high-concentration ammonium bicarbonate solution is added to convert sodium sulfate into sodium bicarbonate as well. If saturated, sodium bicarbonate precipitate will form ； Otherwise, it proves that the concentration was not sufficient at the time, or cooling is required for sodium bicarbonate to crystallize. In this way, the concentration of sodium bicarbonate in the solution is very low, and evaporation crystallization can then be carried out. To know the specific content of each component in advance, CO2 can be used in an appropriate excess amount, and ammonium bicarbonate should be equivalent to sodium sulfate. Specifically, there should be changes in solubility with temperature and a phase diagram.

Is this industrial production or a laboratory chemical experiment? Do you want to remove sulfuric acid An from the solution and then reuse the mixture of sodium sulfate and sodium carbonate? Such simple and straightforward technologies are hard to find even in theory, let alone be technically and economically viable. From an engineering perspective, it achieves your goal, and the technology used is the cheapest among those that can be applied – is that not good enough? After replying to the post at that time, I thought of three methods. 1. Since the solubility of sodium sulfate and sodium carbonate is greatly affected by temperature, and they are also “minor elements”” ； Meanwhile, sulfuric acid AN has a high solubility and its solubility changes little with temperature ； The \"salting-out effect\" of the high concentration of sulfuric acid in the solution can be utilized; by cooling the mixture to around zero degrees, sodium sulfate decahydrate and sodium carbonate decahydrate precipitate out (along with water and salts), thereby removing a considerable amount of water. By further evaporating and crystallizing the effective “mother liquor,” a purer sulfuric acid an can be obtained. Pre-evaporating and concentrating it might yield better results. 2. Sodium hydroxide is added directly to the solution, converting sulfuric acid an into sodium sulfate and ammonia; high-concentration ammonia water can be obtained through distillation (which might be the raw material required for your process). In this way, only sodium sulfate and sodium carbonate remain in the solution. If you say that sulfuric acid An has been removed, then sodium sulfate appears as a byproduct. Then freeze crystallization is used again, but it is likely that a mixed salt of sodium sulfate and sodium carbonate will be obtained. Because, although the solubility of sodium sulfate is more affected by temperature, it is quite strong; as a result, only sodium sulfate remains in the solution. 3. Using a dual-support liquid membrane: We produce membrane modules with two sets of hollow fibers. This membrane process requires the consumption of sulfuric acid and sodium hydroxide, which is equivalent to simultaneously extracting ammonium ions and sulfate ions. Among the two anions, sulfate and carbonate, the anion exchange membrane preferentially extracts sulfate ； Among the two cations, sodium ions and ammonium ions, the cation exchange membrane selectively extracts ammonium ions. This method will certainly achieve the goal of removing sulfuric acid; sulfuric acid and sodium hydroxide are used as driving forces respectively, with sodium sulfate as an additional by-product. And the equipment is very expensive.