Caustic soda is a powerful alkaline substance that can dissolve and extract many things. That is why it is used for many different purposes in various industries.
In the pulp and paper industry, caustic soda helps with dissolving or extracting materials. It is also important for getting alumina from bauxite ore. Moreover, it is very good at cleaning things, such as in breweries, bakeries, and other food processing places.
In water treatment, caustic soda is useful for changing the pH level, making water streams neutral, and lowering corrosion.
In sodium-based chemistry, caustic soda acts as a reaction partner in production processes, adding sodium to final products for different reasons. It is involved in making silicas, silicates, and metasilicates, as well as phosphates, fibers, bleach, detergents, and soaps. Caustic soda is also handy in food processing, such as in making sugar, and in working with vegetable and mineral oils. It is a very flexible and effective substance that is needed for many industrial processes.
Now let's take a detailed look into the applications:
In the chemical industry, sodium hydroxide is used to make sodium metal and electrolyze water. Sodium hydroxide or sodium carbonate is used in the production of many inorganic salts, especially in the preparation of some sodium salts (e.g. sodium tetraborate decahydrate, sodium silicate, sodium phosphate, sodium dichromate, sodium sulfite, etc.). Sodium hydroxide or sodium carbonate is also used in the synthesis of dyes, drugs, and organic intermediates.
Caustic soda solution is one of the most important ingredients for the production of different types of household and industrial detergents. It is also versatile for the production of different kinds of cleaners, such as car wash liquids, hand washing liquids, and concentrated cleaners for tough surfaces, as well as rust and germ removers. It is also widely used for sanitizing bottles in wine production, and for treating ceramic and metal materials.
Caustic soda has many uses in water treatment, such as water purification; softening of hard water; pH adjustment of water; wastewater neutralization; heavy metal removal from water by precipitation; and ion exchange resin regeneration, among others.
Caustic soda can lower the hardness of water by neutralizing it in sewage treatment plants. It can also act as a regenerating agent for ion exchange resin regeneration in the industrial sector. Sodium hydroxide has a high alkalinity and solubility in water, which makes it easy to measure and use in various water treatment fields.
Sodium hydroxide of pharmaceutical quality is a necessary intermediate in the making of a broad range of pharmaceutical products. It is mainly used as a sodium source for anti-flu medicines, such as polopyrin, and for making salicylic acid and sulfonamides.
The printing and dyeing industry uses caustic soda solution to dye cotton fabrics. First, they remove the covers on the cotton fibers, such as wax, grease, pectin, etc., by soaking and boiling them in a weak alkaline solution at a suitable temperature. Then, they expand and soften the dye before dyeing, so that it can reach the inner layer of the fiber. A brief treatment with a strong caustic soda solution can make the fiber molecules align and enhance the color of the fabrics.
This also corrodes the fine fibers (velveteen) on the fiber surface, making the dyeing more even and avoiding uneven shades.
The cotton printing and dyeing industry requires a lot of caustic soda. Caustic soda can also be used to make alkali cellulose from cellulose. Then, the alkali cellulose is turned into cellulose xanthogenate with carbon disulfide, dissolved in weak alkali to form viscose liquid, and then spun and solidified to produce viscose fiber. This is commonly known as artificial cotton, artificial wool, and artificial silk in the market. It takes 1 ton of caustic soda to produce one ton of artificial wool.
Caustic soda flakes are essential for the papermaking industry. They are used to boil and bleach paper sheets because of their high corrosiveness. The main sources of papermaking are wood or grass, which have cellulose and a lot of non-cellulose (lignin, gum, etc.). The fiber can be treated with chemicals. The raw materials are steamed and boiled with ferrous sulfate or alkaline solution, and then the dilute alkali is used to remove the non-cellulose components and produce the pulp that mainly consists of cellulose. This pulp has long fibers and strong paper tensile force.