Alkali Sulfide_Industrial Additive

Property
Purpose
Production methods
Hazardous Characteristics
Accidental leakage measures
Effects of sulfide alkali and oxidizing agents on sulfur dye dyeing

Property
Alkali sulfide is the common name of sodium sulfide, which is a colorless crystalline powder at room temperature. It has strong hygroscopicity and is easily soluble in water. The aqueous solution has a strong alkaline reaction and will cause burns when it touches the skin and hair. The aqueous solution will slowly oxidize into sodium thiosulfate, sodium sulfite, sodium sulfate and sodium polysulfide in the air. Since sodium thiosulfate is generated quickly, the main product of oxidation is sodium thiosulfate. It deliquesces in the air and undergoes carbonation and deterioration, constantly releasing hydrogen sulfide gas. The color of industrial alkali sulfide is pink, brownish-red, or earthy yellow due to the presence of impurities. Its specific gravity, melting point, and boiling point also vary due to the influence of impurities.
There are currently 31 alkali sulfide production enterprises in the country, with a total production capacity of approximately 950,000 tons, mainly distributed in the central and western regions where resources are concentrated, such as Shanxi, Inner Mongolia, Sichuan, Gansu, Xinjiang, and Qinghai. The output in 2000 was only 300,000 tons, and the actual output in 2009 was nearly 800,000 tons. The world financial crisis had little impact on the industry’s exports, with annual exports of 140,000 tons and foreign exchange earnings of US$46.36 million, basically the same as in normal years. Due to the influence of domestic and international markets, the projects under construction still have a production capacity of 300,000 tons.

Purpose

Alkali sulfide is a basic chemical raw material, widely used in textiles, dyes, pigments, printing and dyeing, leather, papermaking, mineral processing, rubber, medicine, pesticide industries and manufacturing aerospace fields Polyphenylene sulfide plastic, etc.
It is used in the dye industry to produce sulfur dyes and is the raw material for cyan sulfide and sulfide blue. In the printing and dyeing industry, it is used as a dyeing auxiliary to dissolve sulfur dyes. In the tanning industry, it is used to hydrolyze raw hides and skins, and is also used to prepare sodium polysulfide to accelerate the soaking of dry hides in water to help soften them. In the paper industry, it is used as a cooking agent for paper. In the textile industry, it is used for denitrification and nitrate reduction of man-made fibers, and as a mordant for dyeing cotton fabrics. It is used in the pharmaceutical industry to produce antipyretics such as phenacetin. In addition, it is also used to make sodium thiosulfate, sodium hydrosulfide, sodium polysulfide, etc.

Production method
(Pulverized coal reduction method) Sodium sulfate is mixed with pulverized coal in a mixer and then added to the converter. The reduction reaction is carried out at high temperature. The crude alkali obtained by the reaction is leached, filtered, evaporated and then tableted to obtain alkali sulfide.

Hazardous Characteristics
Crystalline sodium sulfide is a strongly alkaline corrosive. Anhydrous sodium sulfide is a pyrophoric substance. Crystalline sodium sulfide reacts with acids, emitting toxic and flammable hydrogen sulfide gas. Slightly corrosive to most metals. Sulfur dioxide gas is released during combustion, and sodium sulfide powder can form an explosive mixture with air. Alkali sulfide is easily soluble in water, and its aqueous solution is highly alkaline. It is extremely irritating and corrosive when in contact with skin and mucous membranes. Sodium sulfide nonahydrate can absorb carbon dioxide in the air and produce hydrogen sulfide. When exposed to acids, it will react violently and release a large amount of hydrogen sulfide gas, which can cause serious poisoning if inhaled.

Accidental leakage treatment
Isolate the leaked contaminated area and restrict access. It is recommended that emergency responders wear dust masks (full face masks) and acid and alkali proof overalls. Enter the site from upwind. Small leakage: avoid dust and use a clean shovel to collect in a dry, clean, covered container. You can also rinse with large amounts of water, dilute the wash water and put it into the wastewater system. Large leakage: Collect and recycle or transport to waste disposal site for disposal.

Effects of sulfide alkali and oxidizing agent on sulfur dye dyeing
In the process of dyeing with sulfur dyes, the amount of sulfide alkali and the choice of hydrogen peroxide have a great influence on the dyeing depth and color.
Since sulfur dye itself is insoluble in water, it needs to exist in the form of leuco sodium salt under the action of sulfide alkali. After the dyeing is completed, indigo, which is insoluble in water, is formed under the action of oxidizing agent. In this way, if the dosage of alkali sulfide is insufficient, the sulfur dye cannot be completely dissolved; if the dosage of alkali sulfide is too high, the dyed dye will be re-dissolved in the dye liquor under the action of alkali sulfide, resulting in a waste of dye and a light color.

The choice of oxidant has a certain impact on the change of color light. Oxidants such as hydrogen peroxide and potassium dichromate and copper sulfate oxidize many of the same dyes into different colors, some glowing red and some glowing green.

So controlling the correct dosage of sulfide alkali and selecting appropriate oxidants are critical to the dyeing control reproducibility of sulfur dyes.