Sodium Bicarbonate (Technical) - China

Brief Overview 

Sodium bicarbonate, commonly known as baking soda, is a chemical compound denoted by the formula NaHCO₃. It exists in the form of white crystalline or powder and readily dissolves in water or mineral springs. Found naturally as nahcolite or thermokalite, sodium bicarbonate is versatile, exhibiting amphoteric properties by reacting with both acidic and basic compounds. When it encounters acetic acid, it generates sodium acetate; when it meets bases like sodium hydroxide, it forms carbonates. Heating sodium bicarbonate above 149°C causes it to break down into sodium carbonate, water, and carbon dioxide, forming a stable compound.

Manufacturing Process

Sodium bicarbonate can be produced through the Solvay process, pioneered by Ernest Solvay in the 1860s. This method involves the reaction of sodium chloride with carbon dioxide and ammonia in water. The resulting sodium bicarbonate can then be converted into other compounds like soda ash (Na₂CO₃) or washing soda (Na₂CO₃.10H₂O). The manufacturing process unfolds in the following steps:

1. Creating Sodium Bicarbonate

This initial phase entails the reaction between sodium chloride, carbon dioxide, and ammonia in water. Calcium carbonate serves as the source of carbon dioxide, and the resulting calcium oxide helps separate ammonia from ammonium chloride. Dry ice can also provide an additional source of carbon dioxide. The reaction is as follows:

NaCl(aq) + NH3(aq) + CO₂(s) + H₂O → NH₄Cl(aq) + NaHCO₃(s)

2. Separating Sodium Bicarbonate

The outcome of the first step includes sodium bicarbonate and ammonium chloride. Both compounds are soluble at room temperature, but below this temperature, ammonium chloride exhibits higher solubility than sodium bicarbonate, facilitating the extraction of crystals from the solution. Another method involves the reaction of calcium hydroxide with ammonium chloride, yielding ammonia gas, water vapor, and liquid-phase calcium chloride as products.

Water Treatment Industry

Sodium bicarbonate finds several applications in the water treatment industry due to its alkalinity and ability to neutralize acids. Some of its uses include:

1. pH Adjustment: Sodium bicarbonate is employed to raise the pH of acidic water in both municipal and industrial water treatment processes. It helps neutralize acidic components, balancing the pH to desired levels.

2. Alkalinity Booster: It serves as a source of alkalinity in water, particularly useful in pools and spas where maintaining the proper alkalinity levels is crucial for water balance.

3. Corrosion Control: Sodium bicarbonate's ability to adjust pH assists in minimizing corrosion in pipes and equipment by creating a less corrosive environment.

4. Flue Gas Desulfurization (FGD): In power plants and industrial settings, sodium bicarbonate can be used as a reagent in FGD processes to remove sulfur dioxide (SO2) from flue gases.

5. Wastewater Treatment: It can be utilized to treat wastewater by neutralizing acids, aiding in the removal of heavy metals and other contaminants.

6. Disinfection: Though not a primary disinfectant, sodium bicarbonate can be used in conjunction with other disinfectants to stabilize pH levels and enhance their effectiveness.

Its versatility and relatively low cost make sodium bicarbonate a valuable component in various water treatment applications, contributing to improved water quality and safety.