How to cauterize sodium sulfate into sodium hydroxide or sodium carbonate,
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The by-product here is sodium sulfate; it’s a shame to discard it, but no one will buy it if it’s not discarded. Since what we start with is sodium hydroxide, is it possible to convert sodium sulfate back into sodium hydroxide or sodium carbonate? It’s better for the substances used in this conversion to be inexpensive, as high costs would render recycling pointless.
A problem that several generations of postdocs have failed to solve – so difficult! 20 years ago, some people promoted the use of natural soda ash in reaction with lime to produce caustic soda; it’s not clear whether this method is now used on an industrial scale, but the solubility of calcium sulfate is much higher than that of calcium carbonate.
Sodium carbonate can be converted into sodium hydroxide through causticization, and the efficiency of this process is quite high. However, in my experiments, when sodium sulfate was causticized using calcium oxide, the efficiency was very low
The causticization of sodium sulfate to produce sodium hydroxide is a process that has been heard of but not actually seen; on the other hand, it’s quite easy to causticize sodium carbonate to obtain sodium hydroxide, with a conversion rate of around 80-85%. However, when the concentration of sodium carbonate exceeds 15%, the conversion rate drops. In paper mills, black liquor is burned and then causticized using quicklime to yield sodium hydroxide, and this process is widely used in paper manufacturing.
If it were economically viable to cauterize sodium sulfate into sodium hydroxide, someone would have done it already.
Leaving out water, carbon dioxide, and calcium sulfate (sulfur dioxide), the top waste substances in chemical production, in terms of quantity, are sodium chloride as the first, sodium sulfate as the second, calcium chloride as the third, ferric sulfate plus ferrous chloride as the fourth, and ammonium chloride plus sulfuric acid anhydride as the fifth. (Don’t take this seriously; there is no data to support it.) China discharges hundreds of thousands, or even tens of millions of tons, of sodium chloride in wastewater each year. One ton of industrial salt (sodium chloride) costs 300 – 500 yuan, while one ton of industrial-grade sodium sulfate costs 500 – 800 yuan. Sodium chloride in wastewater can be refined, purified, and concentrated to serve as a raw material for chlor-alkali processes to produce corresponding acids and bases. But ammonium chloride won’t work, nor will sodium sulfate and sulfuric acid an.
There must be methods, but they certainly aren’t cost-effective at the moment. I think those who have studied inorganic chemistry are reluctant to spend time on this area; perhaps in the future effective methods from an economic perspective will be developed.
In the crude phenol recovery unit of Yunnan Jiehua Group’s coal tar plant, sodium hydroxide is used to extract the phenols from the middle oil fraction, converting them into sodium phenolate. This sodium phenolate is then acidified with sulfuric acid to yield crude phenol and sodium sulfate. Sodium sulfate is subsequently converted back into sodium hydroxide using lime, completing one cycle.
Some people carry out a double displacement reaction using sodium sulfate and *ao acid an, to obtain sodium nitrate and sulfuric an. It is said that sodium nitrate costs 2,500 yuan per ton, while ammonium chloride costs 800 yuan per ton; these are the figures I learned about in the past one or two years.
Could yjylqh provide more details on the situation regarding the production of sodium sulfate through lime causticization at Yunnan Jiehua Group?
Alkali treatment must be a reaction between lime and carbonates. In the case of sodium sulfate for alkali treatment, it seems that economic benefits cannot be achieved after going through certain complex processes; of course, new processes might emerge, but as far as I’m concerned, there is no good solution.