Caustic soda – characteristics and use
Caustic soda, also known as sodium hydroxide, is an inorganic white substance with a crystalline structure. It exhibits strongly hygroscopic properties and in combination with carbon dioxide in the air, it easily forms sodium carbonate. To avoid absorbing moisture from the surroundings, caustic soda must be stored in tightly sealed vessels or special bags. Sodium hydroxide is characterized by extremely high solubility in water, with which it reacts by producing large amounts of heat, thus forming a highly caustic soda lye. The caustic soda water solution is non-flammable and odourless and also shows high corrosivity to metals, especially in the presence of moisture. Sodium hydroxide is an extremely dangerous substance and it should be borne in mind to be very careful in its presence. Caustic soda vapours cause pain and watery eyes, as well as irritation of the mucous membrane of the nose and throat, resulting in a strong burning sensation. In contact with skin, caustic soda causes chemical burns, which, after prolonged exposure, may even cause cell necrosis. In order to ensure adequate protection, it is therefore essential to use appropriate personal protective equipment, such as latex gloves, face masks and special clothing and footwear. If you are thinking of buying caustic soda, you should take into account all the above-mentioned aspects.
Based on data provided by GVR (Grand View Research), caustic soda producers in 2015 produced a total of over 74 million tonnes. It is forecasted that this number may increase up to 99 million tonnes in 2024, which gives an average increase of around 3.2% per year. As for the financial side of the market, it is estimated that its value will reach as much as 46.31 billion dollars by 2024. Such a high demand for sodium hydroxide is caused by its increasing consumption in many branches of industry, e.g. in the pulp and paper industry or in the textile industry. This fact may please producers and distributors of sodium hydroxide, whose profits from wholesale will certainly grow. In addition, an increasing demand for the use of PVC in construction has been observed. This directly translates into an increase in NaOH demand on the market, and thus also on the price of caustic soda. It is used for the production of many building materials, such as epoxy resins, polycarbonates or the already mentioned polyvinyl chloride.
Distributors of caustic soda flakes and beads observe the largest demand for it in the Asia-Pacific region – around 55% of the total production of this substance is consumed in this area. This is mainly due to the dynamically developing textile industry and the pulp and paper industry, especially in such countries as India and China. In Europe, according to the report prepared by GVR, the annual increase in demand for caustic soda will be stable at 2.8% in the period from 2016 to 2024. On our domestic market, the sale of flaked caustic soda is marginal. Local customers definitely prefer to buy ready-made soda lye. One of the largest producers of this product in Poland is PCC Rokita SA. In addition to soda lye, the PCC Group is also the only producer in Poland involved in the production of caustic soda flakes, which are sold within approximately 80 markets at wholesale prices. The most important recipients of this raw material are Italy, Brazil, Algeria and China. It is estimated that the price of caustic soda will continue to grow over the next few years. This is mainly caused by the limited number of producers of this substance and constantly increasing demand for it at the same time. This may lead to a situation in which more enterprises ask themselves – where to buy sodium hydroxide?
Sodium hydroxide can be produced by various methods. The most popular is the mercury, diaphragm and membrane processes. The latter one is the most promising and the fastest growing. Due to, inter alia, lowering the cost of production of sodium hydroxide, it will undoubtedly replace the other two processes over time. Membrane electrolysis is a relatively modern method, based on the use of ion-exchange membranes, which were developed in the early seventies of the twentieth century. Their invention allowed the construction of the first industrial membrane installation in Japan in 1975.
The introduction of the EU Directive in 2013 had a significant impact on moving away from the use of mercury cell technology by European producers in the chlor-alkali industry. According to its content, the method of chlorine production through the use of amalgamated electrolysers was allowed only until the end of 2017. The decision to limit the use of mercury in installations producing alkali is associated primarily with its high toxicity to humans and the environment. The introduction of such legal regulations has contributed to changes on the soda market. Due to the need to close mercury installations, the availability of caustic soda in the European Union has decreased, which automatically caused fluctuations in the prices of this product.
The vast majority of chlor-alkali installations built after 1987 use the membrane process. This is due to the many advantages of membrane electrolysers compared to mercury and diaphragm cells. These are mainly such features as:
In the membrane process, the anode and the cathode are separated from each other with an ion-exchange membrane that does not let water through. An aqueous solution flows through the anode space, in which chloride ions are found. They are oxidized to chlorine gas. In turn, hydrated sodium ions migrate through the membrane to the cathode space. Demineralized water is also introduced to the process, thanks to which hydrogen gas and hydroxide ions are formed. In the next step, sodium ions together with hydroxyl ions form a soda lye, which is concentrated to about 35% by recycling brine solution before it is discharged from the electrolyser. The membrane itself prevents the migration of ions from the anode to the cathodic space. Thanks to this, the obtained sodium hydroxide solution does not contain salt, unlike in the diaphragm process. The remaining sodium hydroxide solution (brine) is discharged from the anode space and re-saturated with salt.
Cathodes in membrane electrolysers are usually made of steel or nickel. In addition, they are covered by the so-called active coating (it is a catalyst for the process of hydrogen evolution), which is more stable than the substrate and reduces the potential of the process of hydrogen evolution. The function of the active coating is usually performed by materials such as Ni-S, Ni-Al, Ni-NiO and all mixtures of aluminium and metals from the platinum group. Materials most commonly used as anodes are titanium electrodes with Ru02-TiO2 coating or its various derivatives.
The membranes used in the chlor-alkali industry are usually made of perfluorinated polymers, which consist of one to three layers. First of all, they must be characterized by high durability and stability. It is conditioned by the fact that on the one hand they are exposed to chlorine, while on the other – concentrated solution of lye. In order to ensure adequate mechanical strength, the membranes are reinforced with fibers made of, for example, PTFE. Depending on the parameters of the electrolysers, ion exchange membranes in the chlor-alkali industry can be used from 2 to even 5 years. The secrets of the production of ion-exchange membranes are closely guarded by their producers. The fact that only a few companies produce membranes designed for the electrolysis of alkali metal chlorides proves the degree of complexity of their manufacturing technology.
The use of caustic soda in the industry is practically unlimited. Suppliers of sodium hydroxide successfully deliver the product to a huge number of industries, such as chemical, textile, pulp and paper, cosmetics, pharmaceutical, petrochemical, metallurgy, construction and many other industries.
Sodium hydroxide is one of the basic chemical raw materials. In the pharmaceutical industry, caustic soda flakes or beads can be used, among others for the production of aspirin, salicylic acid and sulfanilamides. In turn, in the cosmetics industry, sodium hydroxide is used in the production of hard soaps and personal hygiene products, such as exfoliating and aseptic masks. Caustic soda is also widely applied in the petrochemical industry. It is used for the refining of crude oil, mineral oils, pitch and bitumen as well as during the extraction of shale gas. However, in refineries and coking plants, caustic soda can be successfully used to modify products derived from the coal coking process. In the metallurgical industry, sodium hydroxide is involved in the process of obtaining aluminium from the processing of bauxite ores.
An extremely important sales market for producers and suppliers of caustic soda is the paper and pulp industry. This substance is used on an industrial scale and bought in bulk by wood pulp companies producing paper. In addition, sodium hydroxide together with sodium sulphate play the role of key components in the separation of lignin from cellulose fibers in the Kraft process. Caustic soda also plays an important role in processes requiring a strongly alkaline environment, such as e.g. delignification or oxidation extraction. In the textile industry, sodium hydroxide is used for the preparation of viscose solutions, which are a reagent not only in the formation of the basic viscose fiber, but also during mercerisation.
If you are in the construction industry and regularly buy sodium hydroxide, you certainly know that it is used as an additive in plasticizers for concrete mixes. Thanks to its use, it is easier to homogenise the cement mixture, which prevents segregation of sand and cement. Caustic soda is also an extremely important raw material in the production of pigments and dyes for paints, e.g. titanium white. It can also be used for the production of water glass, which is used in the impregnation of fireproof fabrics and the production of fire-resistant paints. Sodium hydroxide is also an extremely important component in the production of surfactants, powders and washing liquids, degreasing and softening agents.
Caustic soda is also widely used in farms. Thanks to its cleansing properties it works perfectly as a disinfectant intended for cleaning stables, barns, piggeries and chicken coops. Caustic soda is also extremely popular among beekeepers. Thorough cleaning of the hive surface is achieved by the application of a small percent of soda lye applied with a brush. In the hatching, sodium hydroxide is used to combat diseases of fruit trees and to protect vines. In brewing, soda lye is used to clean beer fermenters. This ensures not only perfect surface disinfection, but also allows quick removal of residual dirt from various tools and tanks used in breweries. In addition, olives are soaked in caustic soda solution in order to preserve them.
As you can see, caustic soda is an extremely universal product. It can be bought directly from producers as a raw material for the production of many other products (e.g. aspirin), as well as from distributors as a finished product (e.g. in the form of a solution, i.e. soda lye) widely used in disinfection.
Sodium hydroxide, due to its hazardous properties, should be purchased only at specialized stores, distribution points or directly at the manufacturers. The purchase of caustic soda from a trusted manufacturer or distributor guarantees that this product has the highest quality. Such a trusted producer is the PCC Group, which is the only company in Poland that produces caustic soda in the form of flakes. For its production a modern method of membrane electrolysis is used, which allows to reduce the cost of production of sodium hydroxide. In addition, the caustic soda obtained in this way is characterized by extremely high quality and purity, thanks to which it meets the requirements of the latest edition of the European Pharmacopoeia. This document defines the basic quality requirements and methods for testing pharmaceutical raw materials. Unlike other distributors of caustic soda, the product offered by the PCC Group is distinguished by extremely low content of chlorides (<200ppm) and iron (<15ppm). In addition, thanks to the raw materials used in the production process, the caustic soda offered by PCC Group meets Kosher requirements. In the PCC Group, we offer sodium hydroxide at wholesale prices – send us an inquiry and check your price.
Any additional information about caustic soda can be found on the PCC Group Product Portal, where you can ask about a product, its availability, price per kg and delivery conditions.
Wondering where to buy caustic soda at wholesale prices? Check our website.
See also: sodium hypochlorite suppliers