JPS6137201B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is characterized in that an alkali metal or alkaline earth metal hydroxide is produced from an aqueous solution containing an alkali metal or alkaline earth metal sulfide, hydrosulfide, polysulfide, or two or more thereof. The purpose is to process various inorganic industrial chemicals such as barium salt, petroleum refining process, various metal scouring and processing processes such as steel manufacturing, and naphtha decomposition ethylene production. The object of the present invention is to provide a processing method for obtaining useful industrial raw materials such as caustic soda from the aqueous solution, which is discharged in large quantities as waste liquid from manufacturing processes, rayon manufacturing processes, city gas manufacturing processes, etc. and is a source of pollution. Several proposals have already been made regarding methods for obtaining hydroxides such as caustic soda from these sulfides. For example, a method of oxidizing alkali metal sulfide using manganese dioxide or manganese ore powder containing manganese dioxide to produce caustic soda and elemental sulfur, or a method of using manganese dioxide as a catalyst and blowing oxygen or an oxygen-containing gas into it. A method of similarly producing hydroxide such as caustic soda and sulfur through oxidation has been proposed. However, when the reaction is actually carried out, in the former method, it is extremely difficult to regenerate the manganese compound obtained as a precipitate after the reaction into manganese dioxide, and it is impossible to regenerate it with aeration oxidation using air or oxygen. Further, even if regeneration is performed by calcination, a significant decrease in the purity of manganese dioxide cannot be avoided, and therefore, it is necessary to constantly supply new manganese dioxide in continuous processing. Even in the latter method, for example, in the reaction of treating sodium sulfide, the yield of caustic soda is good only at the beginning of the reaction, and after that, the production of sodium thiosulfate increases significantly, and the amount of manganese dioxide and the amount of blown gas change. However, it shows the same tendency, and the catalytic action of manganese dioxide is not recognized, and it only functions as an oxidizing agent.In the end, the reaction is the same as the former method, and it causes the same regeneration problem. It has been found that it has. As mentioned above, by using manganese dioxide, hydroxides such as caustic soda can be obtained from sulfides, but manganese dioxide is difficult to recycle and use even though it is an expensive processing agent. There are certain fatal drawbacks in terms of industrial application, and the current situation is that it has not yet been put into practical use. In view of the above-mentioned circumstances, the present inventors have discovered that alkali metal hydroxides such as caustic soda or alkaline earth metal hydroxides can be obtained in high yield from sulfides,
Moreover, as a result of extensive research and experimentation on industrially practical treatment methods, they discovered an innovative method that uses manganese hydroxide, whose main component is manganese 1oxydihydroxide, as the oxidizing agent. . According to research conducted by the present inventors, manganese 1oxyhydroxide is a compound that can produce hydroxides such as caustic soda from sulfides in a high yield, similar to the above-mentioned manganese dioxide, and after use. The manganese compound can be almost completely regenerated into manganese 1oxydihydroxide by aerobic oxidation under strong alkaline conditions and can be recycled. Based on experimental results, using sodium sulfide as an example, it is assumed that the main reaction is Na ₂ S + 2MnO (OH) ₂ → 2NaOH + 2MnO (OH) + S ... (), but in reality xNa ₂ S+2(x-1)MnO(OH) ₂ →NaSx+2(x-1)NaOH +2(x-1)MnO(OH)(x=2~5)
……After passing through the polysulfide generation stage as shown in (), then Na ₂ Sx + 2MnO (OH) ₂ → 2NaOH + 2MnO (OH) + xS ……In which elemental sulfur is liberated from polysulfides as shown in (). it is conceivable that. Figure 1 shows the reaction when manganese hydroxide (as manganese 1oxydihydroxide) was added at 1.2139 g/min (0.763 mol) for 66 minutes to 500 ml (0.282 mol) of a sodium sulfide aqueous solution with a concentration of 44 g/l of _Na 2 S. This is a graph showing the measurement results of redox potential, and it is assumed that the part indicated by a in the figure is the stage of polysulfide generation, and the part indicated by b is the stage of sulfur release. Manganese 1oxydihydroxide is MnO(OH) ₂ ,
Alternatively, it is expressed as H ₂ MnO ₃ etc., and is also called manganese hydroxide ( ₎ or manganese oxide () hydrate _.
It is thought to take the form of This is generally obtained by oxidizing a soluble manganese () salt solution in an alkaline environment with air, etc., and as described later, manganese 1oxy-1 hydroxide {MnO
(OH)}, or manganese hydroxide () {Mn
(OH) ₂ } under strong alkaline conditions, and depending on the conditions, a small amount of manganese 1oxy-1 hydroxide or manganese hydroxide () may be present as a by-product or unreacted. In the present invention, any manganese hydroxide whose main component is manganese 1oxydihydroxide can be used. The amount of manganese hydroxide used is 2 moles or more as 1 oxymanganese dihydroxide per 1 mole of alkali metal or alkaline earth metal sulfide, hydrosulfide, polysulfide, but it is reactive. From the viewpoint of practicality, a range of 2.5 to 3 moles is preferable. Manganese hydroxide, whose main component is manganese 1oxyhydroxide, is generally added to an aqueous solution of sulfides, which is the liquid to be treated, and reacted. There is no harm in adding. Manganese 1oxyhydroxide may be added in the form of dry matter, wet cake, or slurry; however, if slurry is used at a low concentration, the concentration of the caustic soda, etc. produced will decrease and the product value will be lost. Therefore, it is desirable to have as high a concentration as possible. Further, since changes in the concentration of sulfides have no effect on the reaction, it is desirable that the concentration is as high as possible in the liquid to be treated, such as sodium sulfide. As the reaction temperature rises, the production rate of thiosulfate increases. Therefore, it should be carried out at as low a temperature as possible, and a range of 10 to 40°C is preferable. Although this reaction is exothermic and may require cooling to maintain the desired temperature, the temperature can also be controlled by adjusting the rate of addition of the reaction components. After the reaction is complete, the aqueous solution of caustic soda, etc. from which the solids have been separated contains only the water-soluble components that were originally present in the raw material aqueous solution, other than the by-product thiosulfate, and contains no other water-soluble impurities. Since there are no by-products, caustic soda of desired purity can be obtained by controlling raw material purity and reaction conditions. To carry out the method of the present invention industrially, the manganese compounds used {MnO(OH), Mn(OH) _2, etc.) are regenerated into manganese hydroxide whose main component is manganese 1oxydihydroxide. should be reused circularly. Regeneration can be achieved by collecting the manganese compound precipitate and subjecting it to aeration and oxidation under strong alkaline conditions with an oxygen-containing gas such as air. The slurry concentration in this operation is preferably 100 to 200 g/l in terms of solid matter, and the alkali is about 10 to 30 g/l in terms of NaOH. In addition, since the precipitated elemental sulfur is mixed in the precipitate after the reaction, if the precipitate after the reaction is used for regeneration, it should be removed to prevent a decrease in purity. The most reliable way to maintain purity is to dissolve the manganese compound in sulfuric acid, separate and remove the sulfur as a precipitate, and then add alkali (NaOH) to the solution to form manganese hydroxide and oxidize it by air. Other methods may also be used. For example, from the viewpoint of recycling costs, it is also practical to use flotation separation to separate and remove most of the sulfur as scum. In this case, although some manganese compounds are also included in the scum, it is economically advantageous to employ the above-mentioned mineral acid dissolution method only for recovering them. Furthermore, as a practical aspect of the method of the present invention, since the reaction is in a form in which elemental sulfur is liberated through the production of polysulfides as described above, the reaction is treated as two steps, and the polysulfide is produced in the first step. When the production is completed, the manganese compound precipitate is separated and collected, and then a polysulfide solution and a new one are added.
An example is a method of performing a second stage treatment operation of reacting with manganese oxydihydroxide. According to this method, since the manganese compound recovered in the first stage does not contain sulfur, it is possible to regenerate it by aeration and oxidation without going through the above-mentioned sulfur removal treatment, which is extremely advantageous economically. Furthermore, the precipitated manganese compound has a larger volume than when manganese dioxide is used, and in a method in which the precipitate is collected and separated only after the reaction is completed, stirring and over-operation become extremely difficult. In order to avoid this, if the concentration of the reaction solution is lowered, the concentration of the produced caustic soda will be low. Therefore, from these points as well, it can be said that the method of collecting the precipitate before the release of sulfur is effective. The point at which the first stage reaction is completed can be determined empirically, but considering the economic efficiency of operation and ignoring the drop in purity due to trace amounts of sulfur contamination, the main component is manganese 1oxydihydroxide, which is used in the reaction. It is easy to collect the precipitate when a certain amount (usually 2/3 amount) of the amount of manganese hydroxide is used. Further, in order to know this accurately, since the redox potential shows a certain pattern, it is possible to measure this and find the inflection point (point C in FIG. 1) of the measurement curve. Furthermore, according to experiments conducted by the present inventors, the potential at this inflection point is less affected by the concentration of the reaction solution, so if strictness is not required, -500
It is possible to set ~-530mV as the index potential of the inflection point. Examples of the present invention are shown below. The manganese hydroxide mainly composed of 1oxymanganese dihydroxide used in the examples was prepared by adding 126 g of NaOH to an aqueous solution containing 200 g of _MnSO4 .
was obtained by a method in which air was introduced into the slurry containing manganese hydroxide Mn(OH) ₂ precipitate at a rate of 10/min for 4.5 hours. Example 1 A manganese hydroxide slurry (126 g/concentration) containing 1-oxymanganese dihydroxide as the main component was added to 500 ml (0.282 mol) of a sodium sulfide aqueous solution having the following composition discharged from the barium salt manufacturing process (in terms of solid matter). It was added at a rate of 1.2139 g/min and reacted for 66 minutes (0.763 mol as manganese 1oxydihydroxide). The temperature during the reaction was maintained at 20-25°C. Sodium sulfide aqueous solution composition Concentration (g/) Reaction amount (mol) Na ₂ S 44.0 0.282 Na ₂ S ₂ O ₃ 1.32 0.0042 Na ₂ SO ₃ 0.96 0.0038 Product liquid composition after reaction (excluding water in manganese hydroxide slurry) (corrected for sodium sulfide solution) Concentration (g/) Amount produced (mol) NaOH 43.5 0.544 Na ₂ S ₂ O ₃ 1.38 0.0044 Na ₂ SO ₃ 0.85 0.0034 NaOH conversion rate 96.4% Example 2 Sodium sulfide with the following composition Add 10 (5.385 mol) of aqueous solution to 900 g (as manganese 1 oxy hydroxide) of manganese hydroxide wet cake containing 1 oxy manganese dihydroxide as a solid substance.
8.571 mol), stirred and reacted for 10 minutes while maintaining the temperature at 20-25°C, and separated.
Add manganese hydroxide wet cake containing manganese 1oxy dihydroxide as the main component to the liquid again, and add 790g (7.524 g as manganese 1oxy hydroxide) in terms of solid matter.
mol) was added, stirred for 10 minutes to react, and then separated. Sodium sulfide aqueous solution composition Concentration (g/) Reaction amount (mol) Na ₂ S 42.0 5.385 Na ₂ S ₂ O ₃ 1.29 0.0816 Na ₂ SO ₃ 0.5 0.0397 Product liquid composition after reaction (excluding water in wet cake, sulfurization (corrected for soda solution) (1st time) Concentration (g/) Production amount (mol) NaOH 41.3 10.325 Na ₂ S ₂ O ₃ 1.30 0.0822 Na ₂ SO ₃ 0.45 0.0357 NaOH conversion rate 95.8% In separate residue, first stage The sediment is sent to the regeneration tank,
The sediment in the latter stage was subjected to flotation separation to remove sulfur as scum, and the sediment was sent to a regeneration tank. Furthermore, the manganese compound mixed in the scum is dissolved as manganese sulfate by adding 1.05 equivalents of sulfuric acid, and after removing sulfur as an insoluble matter, 1.05 equivalents of caustic soda is added to convert it into manganese hydroxide {Mn(OH) ₂ }. None, sent to regeneration tank. In the regeneration tank, water and caustic soda are added to the total amount of sediment to adjust the alkaline concentration (20g/NaOH), and the
150g/manganese compound slurry, 300/
Air was passed through the reactor for 2 hours at a temperature of 0.degree. Using this, the same aqueous sodium sulfide solution as described above was treated and the manganese compound used was regenerated, and these operations were subsequently repeated. The results are shown in Table 1 (wet/cake moisture etc. were corrected in the same way as in the first test).

[Table] As can be seen from Table 1, the manganese compound does not lose its activity upon regeneration and can be used effectively any number of times.

[Brief explanation of the drawing]

Figure 1 shows 1% of sodium sulfide aqueous solution (44g/).
It is a graph showing the measurement results of the redox potential when manganese hydroxide whose main component is manganese oxydihydroxide is added and reacted. FIG. 2 shows a typical flow sheet for the method of the present invention.

Claims (1)

[Claims] 1. An aqueous solution containing an alkali metal or alkaline earth metal sulfide, hydrosulfide, polysulfide, or two or more of these, and hydroxide containing manganese 1oxydihydroxide as the main component. React with manganese,
A method for treating sulfides, characterized by producing alkali metal or alkaline earth metal hydroxides and elemental sulfur. 2. Reacting an aqueous solution containing an alkali metal or alkaline earth metal sulfide, hydrosulfide, polysulfide, or two or more thereof with hydroxide magnetic acid containing manganese 1oxydihydroxide as a main component, In the method of producing alkaline earth metal hydroxides and elemental sulfur, part or all of the precipitated manganese compound is recovered and regenerated to produce manganese hydroxide whose main component is manganese 1oxydihydroxide. A method for treating sulfides, characterized by reusing them in the above reaction.