Soda ash is either mined from trona mineral or is processed from brines bearing sodium-carbonate. Naturally occurring trona is largely found in the Green River basin Wyoming. It is also found in lakes of California, Botswana, Egypt, Turkey, China and Nigeria. Trona, chemically sodium sesquicarbonate Na2CO3•NaHCO3•2H2O, contains highly pure combination of sodium carbonates which is mined and processed into to high quality soda ash.
In ancient times sodium carbonate was used by Egyptians to make glass ornaments and vessels. It was also used for medicinal purposes, baking bread and glass making by Romans. Until the middle of the 19th century, sodium carbonate was extracted from ashes of plant growing in sodium rich soil. Since they were being extracted from ashes of sodium rich plants they got named as “soda ash”. Soda ash light differs from soda ash dense only in physical characteristics such as bulk density, particle size and shape.
Soda ash can be produced from natural soda reserves and production from lake waters. Natural soda ash containing brines and deposits were found in the United States at Searles Lake, Califonia and Green River, Wyoming in the late 1800s. During the first half of the 1900s the Searles Lake deposit was commercialized and the production facilities improved and expanded. In 1938 large deposits of trona, Na2CO3•NaHCO3•2H2O was found in the Green River basin. Deposits of sodium carbonate are found in large quantities in Botswana, China, Egypt, India, Kenya, Mexico, Peru, Turkey, and the USA. The major natural sodium carbonate deposits include trona from Green River, Wyoming, USA, brine from Searles lake, California, USA, brines from Lake Magadi, Kenya and brines from Sua pan in Botswana.
Trona is a relatively rare, non-metallic mineral. The pure trona material contains 70.39% of sodium carbonate. Because trona is an impure sodium sesquicarbonate mineral (Na2CO3•NaHCO3•2H2O), it has to be processed by calcinations of the excess carbon dioxide and removing water to produce soda ash.
It is synthetically produced by various chemical processes such as Solvay, Leblanc & Hou’s process with different starting raw materials. Most commonly & widely used manufacturing process is Solvay process.
The Solvay process is also known as the ammonia soda process. The Solvay process was developed by the Belgian Ernest Solvay (1838 – 1932) in 1861. This process reduced the
operating cost and environmental impact. The Solvay process is the most accepted technology for producing synthetic soda ash because the investment and maintenance costs are low compared to other processes.
The Solvay process is still the dominant production route for soda ash. The basic raw materials that are used in this process include salt, limestone and coke or natural gas and also ammonia as a cyclic reagent. In this process the ammonia reacts with carbon dioxide and water to form ammonium bicarbonate. The ammonium bicarbonate is then reacted with salt to form sodium bicarbonate, which is calcinated to form sodium carbonate. Chloride is formed as a byproduct and is neut
ralized with lime to produce calcium chloride. Almost all the ammonia used in the reactions is recovered and recycled. The Solvay process can be summarized by the following theoretical global chemical reaction, which involves two main components which are sodium chloride and calcium carbonate.
2NaCl + CaCO3 → Na2CO3 + CaCl2
The above reaction cannot be applied directly in practice; the Solvay process needs the use of other substances and also many different process steps before getting to the final product which is soda ash. The Solvay process includes the following stages:
1. Production of a saturated salt solution.
NaCl + H2O
2. Burning of limestone and the CO2 recovered while CaO is used in stage 7
CaCO3 → CaO + CO2
3. Saturation of the salt solution with ammonia
NaCl + H2O + NH3 + CO2
4. Precipitation of bicarbonate by adding carbon dioxide
NaCl + H2O + NH3 + CO2 → NH4Cl + NaHCO3
5. Filtration and washing of sodium bicarbonate
6. Thermal decomposition of sodium bicarbonate to sodium carbonate
2NaHCO3 → Na2CO3 + H2O + CO2
7. Production of milk of lime
CaO + H2O → Ca(OH)2
8. Recovery of ammonia by distillation of the mother liquor from stage 4 with milk of lime
2NH4Cl + Ca(OH)2 → 2NH3 + CaCl2 + 2H2O
The Leblanc or black ash process was discovered in the period around between 1825 and 1890 by the French physician Nicolas Leblanc.This synthetic process was named after its inventor.In this process, soda ash was produced from common salt, sulfuric acid, coal and limestone. Sodium chloride reacts with sulfuric acid to produce sodium sulfate and hydrochloric acid. The sodium sulfate is then roasted with limestone and coal and results into sodium carbonate and calcium sulfide mixture. The sodium carbonate and calcium sulfide mixture is also known as black ash. Black ash is then leached with water to extract the sodium carbonate. The Leblanc process which is now of only historical interest, is based on the following chemical reactions:
1. 2NaCl + H2SO4 →Na2SO4 + 2HCl
2. Na2SO4 + 2C → Na2S + 2CO2
3. Na2S + CaCO3 → Na2CO3 + CaS
Hou’s Process uses ammonia and carbon dioxide for generation of sodium carbonate. This Process is not adopted due to its high manufacturing cost when compared to Solvay process. In this Process ammonium chloride is generated as a by product which is sellable. The reaction for the same is as follows
NH3 + CO2 + H2O → NH4HCO3 NH4HCO3 + NaCl → NH4Cl + NaHCO3
Soda Ash Light has a numerous industrial applications such as:
In textile dyeing, pH plays very important role. When soda ash is added it changes the pH of cellulose fibre and fibre reactive dye, fibre molecules are activated which chemically attack the dye, so that the dye reacts with the fibre and permanently holds the dye onto the fibre.
Soda ash can be added at three different stages i.e before, during or after dyeing. Generally it is added before the dye in tie-dye. Garments are tie or left loose. Half or one cup of soda ash is added per 3.875 litre of water as a makeup solution, and then the material is soaked for five minutes to hour. Then the dye is applied to soda ash pre-soaked garments. Soda ash is added with the dye, generally used with dye painting. However during immersion dyeing and low water immersion dyeing, soda ash is added after dye.
Basically in textile dyeing the simple requirement is to increase the pH (alkalinity) of the reaction (pH around 10.5-11). However the ideal or exact pH depends on individual dye colour & fibre used.
Apart from soda ash various other chemicals caustic soda (NaOH), trisodium phosphate (TSP), sodium silicate, acetic acid, sodium bicarbonate etc, can be used to reach ideal pH. But handling pure caustic soda requires trained chemists as it is quite dangerous. Also if you use a bit too much or too little of soda ash it will increase the pH close to correct pH, but not the same with caustic soda. Low pH will not work and too high pH is dangerous to both fibre as well as people handling it.
Soda ash light is used in soap and detergent industries where it acts as filler and helps in providing a smooth finish to the finished product.
- It is added in detergent to alter their physical characteristics and properties.
- The objective of adding it to detergent is to make detergents fluid or to turn fluidized detergent into powder form.
- It also improves the cleansing performance.
- Soda ash is also used as a raw material in the production of different detergents ingredients such as sodium percarbonate, sodium silicate which is a corrosion inhibitor extending the lifetime of washing machines.
The high alkalinity of soda ash allows it to act as a solvent in removing a wide range of stains. It is often used in commercial detergent mixtures to treat hard water. The soda ash binds to the minerals which make water hard and allows the detergent to be absorbed into fibers properly to clean clothes.
The addition of soda ash prevents hard water from bonding with detergent, allowing for a more even distribution of the cleaning agent during the washing cycle. Typically soda ash is used in detergents. The products function as a builder in the formulations of soaps, detergents and other cleaning compounds, preparing wash water so it achieves the optimal level of soil removal. Soda ash also adds benefits as such by aiding agglomeration, being a carrier for surfactants and as an alkali source for pH adjustment.
A large number of formulated domestic products, soaps, scouring powders, soaking and washing powders etc. have a varying content of soda ash. More and more, quality soda ash is being used in the production of high performance compact powders for both laundry and dish washing. These higher performing and environmentally-friendly products offer greater value to the consumer.
Raw material for other chemicals production
Soda ash is an acknowledged source of sodium ions. It also aids the solubility and reactivity of many inorganic compounds in water. As such, it is used as a major raw material for the economical production of sodium phosphates, sodium silicates, chrome chemicals and photographic chemicals. It is also used in the production of sodium bicarbonate (baking soda), which is an essential ingredient in the beverage, coatings, detergents, food, dialysis, and personal care markets.
For many of applications, soda ash is interchangeable with caustic soda, while offering a cost advantage. Thus, it can be used as a functional substitute for caustic soda in many applications, such as:
- pH adjustment/acid neutralization
- Manufacturing of sodium chemicals including sodium phosphates, sodium sulphate, sodium sulphite, sodium acetate, sodium nitrite and sodium citrate
- Kraft pulping
- Flue gas de-sulfurization
Sodium carbonate is a food additive (E500) used as an acidity regulator, anticaking agent, raising agent, and stabilizer. It is one of the components of kansui, a solution of alkaline salts used to give ramen noodles their characteristic flavor and texture. It is also used in the production of snus (Swedish-style snuff) to stabilize the pH of the final product.
Sodium carbonate is also used in the production of sherbet powder. The cooling and fizzing sensation results from the endothermic reaction between sodium carbonate and a weak acid, commonly citric acid, releasing carbon dioxide gas, which occurs when the sherbet is moistened by saliva.
It is used as fluxing agent during the manufacture of glass. It also regulates the temperature in the furnace. It is responsible for equal distribution of energy. It supports in shaping of glass. Silica is the glass forming oxide, lime provides chemical stability and soda ash acts as the fluxing agent. Soda ash plays a vital role by reducing the furnace temperature necessary to melt the silica used, thus reducing the energy required to produce glass.
It is used to break down the non cellulose materials, it is also used in the preparation of fiber.
It is used in food industries, manufacturing of sweeteners in beverage industry, cotton industry, buffer agent, pH regulator, soap industry and many other chemical industries.