Sodium thiosulfate (Na2S2O3) is a common raw material for the production of chemicals, which is widely used in the fields of photography, printing and dyeing, medicine and analytical chemistry. In this paper, we will introduce a manufacturing method of sodium thiosulfate, which is prepared by chemical reaction with sodium hydroxide (NaOH), sodium sulfide (Na2S) and sulfuric acid (H2SO4) as raw materials.
I. Preparation of raw materials
1. Sodium hydroxide: choose industrial grade sodium hydroxide, purity ≥ 96%, white solid particles. Sodium sulfide: industrial grade sodium sulfide, purity ≥95%, yellow crystalline particles.
3. Sulfuric acid: choose industrial grade sulfuric acid, concentration is about 98%, colorless transparent liquid.
II. Reaction Principle
The equation of the preparation of sodium thiosulfate is: 2NaOH + Na2S + H2SO4 → 2Na2S2O3 + 2H2O. In this reaction, sodium hydroxide and sodium sulfide firstly react to produce sodium hydrosulfide (NaHS), and then sodium hydrosulfide reacts with sulfuric acid to produce sodium thiosulfate and water.
3. Manufacturing process
1. Ingredients: Add sodium hydroxide, sodium sulfide and sulfuric acid into the reaction kettle according to a certain proportion and stir well.
2. Reaction: Control the reaction temperature within a certain range, let the raw materials fully react to generate sodium thiosulfate.
3. Crystallization: Cool the reaction liquid to a certain temperature, so that the sodium thiosulfate crystals precipitate.
4. Centrifugal Separation: Separate the crystals from the mother liquor by centrifugal machine to get the wet product of sodium thiosulfate.
5. Drying: Dry the wet product sodium thiosulfate to get dry sodium thiosulfate product.
4. Precautions
1. Control the reaction temperature: too high temperature may lead to the occurrence of side reaction and affect the product quality.
2. Adjustment of pH: During the reaction, pH needs to be adjusted at the right time to promote the reaction.
3. Centrifugal separation conditions: choose suitable centrifugal speed and time to ensure the effective separation of crystallization and mother liquor.
4. Selection of drying method: according to the nature of the product and production conditions, select the appropriate drying method to ensure product quality.
V. Product quality standard
The product of sodium thiosulfate produced should meet the following quality standards: appearance of white or slightly yellow crystalline particles, purity ≥ 98%, water insoluble matter ≤ 0.1%, free alkali ≤ 0.5%, sulfate ≤ 0.05%.
VI.Waste treatment
Waste generated in the production process should be properly treated to avoid pollution of the environment. For example, mother liquor can be recycled and reused after treatment, solid waste should be classified, and hazardous waste should be disposed safely according to relevant regulations.
In conclusion, the manufacturing method of sodium thiosulfate involves a number of links and considerations, and in order to ensure product quality and production safety, it is necessary to strictly control each process parameter and operation process. At the same time, waste should be properly disposed of in order to realize the green and sustainable development of the production process.
