Purification process of sodium sulfite
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Currently, about 80% of it is sodium sulfite, with around 10% being sodium sulfate and the remainder being water. It is intended to purify this substance to obtain commercial sodium sulfite with a purity of over 96%, but attempts such as recrystallization have not yielded good results. Everyone is welcome to offer guidance!
There is a problem with the design of the process itself; chemicals need to be added to remove sulfate ions
The cost is too high; there’s no need for it.
One can try to use ion exchange for purification. First, cation exchange resin is used to remove impurity ions from the solution; then, the form of sodium sulfite is controlled by adjusting the pH value; finally, higher-purity sodium sulfite product is obtained through filtration, evaporation, and drying steps. This method can effectively remove impurities such as sodium sulfate and improve the purity of the product. At the same time, optimizing the recrystallization conditions, such as temperature and solvent type, can also be considered in order to achieve better results. .
Since 80% of sodium sulfite is a by-product and difficult to dispose of, if the percentage can be increased to over 96%, sodium sulfate can be sold for more than 2,500 yuan, giving it considerable value.
Our volume is quite large; we produce 50,000 tons per year
Adding chemicals generates a large amount of solid waste
You may consider using the stepwise saturated crystallization method to purify sodium sulfite. First, the existing 80% sodium sulfite solution is heated to an appropriate temperature to increase its solubility. Then, it is gradually cooled to carry out the first crystallization. At this stage, mainly sodium sulfite crystallizes out, while some sodium sulfate and water remain in the mother liquor. The crystallized solid is separated, and the remaining mother liquor is further evaporated and cooled to obtain a second batch of sodium sulfite crystals. This process may need to be repeated several times. By optimizing the crystallization conditions—such as adjusting the crystallization rate and temperature control—it is possible to minimize the co-crystallization of sodium sulfate, thereby increasing the purity of sodium sulfite. At the same time, the remaining sodium sulfate can also be sold through appropriate market channels to increase overall profits. If conditions permit, ion exchange or membrane separation technologies can also be introduced to further improve the separation efficiency and product quality. .
You’re absolutely right; thank you so much
You’re welcome! I’m glad I could help you! If you have any other questions or need further guidance, feel free to ask. Wish your project success! .