What are the functions of sodium hydroxide solution

The function of sodium hydroxide solution is to dissolve carbonate and bicarbonate salts. It is used in many industrial processes such as extracting sodium carbonate from brine, refining sugar and purifying drinking water. There are many functions of sodium hydroxide solution, they includes;

1.CO₂ removal

During the process of obtaining sodium hydroxide, Carbon dioxide is released. The CO₂ is removed using an absorbent in liquid phase or gas phase. This absorbed gas can be recycled and used for other processes. Also, some of the gas may be released into the atmosphere since it is a byproduct of producing chemicals from natural gas; this action helps to remove CO₂ that is already present in the atmosphere.

2.Decolorization of wood pulp for paper making

Decolorization of wood pulp for paper making purposes uses sodium hydroxide as a decolorizer (treatment agent) for softwood pulp. Sodium hydroxide is added with the pulp in a 3:1 ratio.

3.Process of producing sodium carbonate from brine

Sodium carbonate is produced from brine in sodium hydroxide solution by the addition of calcium hydroxide. The salts are dissolved to liberate carbon dioxide. The sodium carbonate solution should be left overnight in order to allow the solid calcium hydroxide to precipitate out of solution and form solid crystals, thus consummating a chemical reaction between two liquids bicarbonate and salt, creating sodium carbonate.

4.Removing impurities from chemicals

Due to the different chemical compositions of the impurities in chemicals, some are more readily removed by alkaline boiling than others. In this process, alkali is added to a pressure cooker and then heated for one and a half hours; after cooling down the process continues with two washings using distilled water. The impurities will become solid at the bottom of the vessel.

5.Used in cleaning wool

Sodium hydroxide is used to clean woolen fabrics which have been stained by mildew (microorganism growth on materials due to humidity). It washes off excess fat and oils from woolen cloths. It reacts with dye in wool and removes it. The washing can be done with hot water and soap or with cold water and detergent. The smell of the solution is also removed by washing.

6.Used in extracting sodium carbonate from brine

Sodium bicarbonate is obtained by dissolving sodium carbonate in a cold, saturated aqueous solution of sodium hydroxide. The precipitate formed has to be separated by filtration or centrifugation, this process promotes the solid formation of calcium hydroxide, which penetrates into the solution, thus forming a calcium carbonate precipitate from which sodium carbonate can be easily recovered by distributing the desired amount of it on a filter and washing it with distilled water. The calcium carbonate can be used as an additive in cosmetics, water purification and animal feed.

7.Enzyme washing for wool processing

Sodium hydroxide can be used to remove the fleece from a sheep's body by using similar procedures as those used for removing wool from the washing table. This is done by submerging the whole sheep's body in a tank of warm sodium hydroxide solution for half an hour. The alkali dissolves the fats which are then washed away with water and soap. The process leaves the sheep completely hairless except for the skin on its head, legs and around its tail.

8.Used in the paper manufacturing process

Sodium hydroxide solution is used in the paper manufacturing process and it is also used to make a strong bond between fibres during paper making. It can be added during paper making or after completing the sheet, either before or after drying. The strength of the bond depends on how much sodium hydroxide solution is added. The more sodium hydroxide added, the more stiffer and stronger the bond becomes. This is another function of sodium hydroxide solution.

9.Used in bleaching

Sodium hydroxide is used in bleaching textiles and it is also used to remove water-soluble dyes from fabrics. The process involves the dipping of the fabric into a solution of sodium hydroxide and then rinsing it with hot water which oxidizes the natural colour of the garment or eliminates other contamination such as grease or blood. As a result, not only does the bleach make the clothes white but it preserves them from natural deterioration. This is an effective way of eliminating stains and harmful chemicals on white clothes.

In conclusion, function of sodium hydroxide solution is to dissolve carbonate and bicarbonate salts. The two main uses of sodium hydroxide are in soap making and in chemical manufacturing. Soap making is for washing clothes or for personal use in the form of shower gels, body-washes, hand soaps, etc. Those involved in this industry include the soap manufacturing companies like Unilever and Procter & Gamble.