Basic knowledge of calcium carbonate

Basic knowledge of calcium carbonate：

1. Overview: Calcium carbonate (CAS No. 471-34-1): is a very common inorganic compound widely distributed on earth. Molecular formula: CaCO3; molecular weight: 100.09. According to its molecular weight, the calcium content of calcium carbonate is 40%.

Note: The CAS number is the number for all chemical substances in the American Chemical Abstracts.

2. Classification of calcium carbonate:

2.1 According to the preparation process, it can be divided into two types: light calcium carbonate and heavy calcium carbonate.

2.2.1 Light calcium carbonate:

Calcium carbonate obtained by chemical synthesis is called Light calcium carbonate (LCC for short) or Precipitated calcium carbonate (PCC for short). There are two main methods of production:

a. Precipitation method: The starting material limestone (grey or black in appearance) is calcined to form calcium oxide (which releases carbon dioxide at the same time), calcium oxide + water to form calcium hydroxide, and calcium hydroxide + carbon dioxide to synthesize calcium carbonate. The reaction equation is as follows:

CaCO₃                   CaO+ CO₂;

CaO+H₂O         Ca(OH)₂;

Ca(OH)₂ + CO₂                  CaCO₃;

The raw material calcium carbonate of Jiande Zhengfa Pharmaceutical Co., Ltd., Zhejiang Province adopts this process route.

Advantages and disadvantages of this method:

The advantages are: the starting material is cheap; the cost of the synthesis process is low; there is no added substance, and there is no need to remove the impurity residue.

Disadvantages: This process has poor ability to remove impurities, and product quality mainly depends on raw materials.

b. Calcium chloride process:

To synthesize calcium carbonate with calcium chloride and ammonium bicarbonate, the reaction equation is as follows

CaCl₂+ NH₄HCO₃                  CaCO₃+ NH₄Cl

Advantages and disadvantages of this method:

Advantages: The production process line is short, and it is synthesized in one step.

Disadvantages: The price of the starting material is generally higher than the price of the finished product under the same specification, which is not economically feasible; there is a large amount of chloride ions in the product, which needs to be washed repeatedly, and the cost is high (the calcium carbonate of the original production reagent uses this process , it is said that every ton of calcium carbonate needs to be washed with 15 tons of water), because the pharmaceutical standard has requirements for chloride ions (not more than 0.03%); the reaction by-product ammonium chloride is unstable and easy to decompose to produce ammonia gas, the product will have Unpleasant smell.

2.2.2 Ground calcium carbonate:

Calcium carbonate obtained by physical grinding of natural calcite ore is heavy calcium carbonate (Heavy calcium carbonate, referred to as HCC), and there is an English translation Ground calcium carbonate, referred to as GCC.

The advantages and disadvantages of this process:

Advantages: The production process is simple; the starting material has high purity and few impurities, resulting in the content and impurity level of the finished product being generally higher than that of light calcium carbonate.

Disadvantages: The specific gravity is large, the sedimentation in water is fast, and it cannot be used in many liquid products; there is no chemical synthesis process, and the API calcium carbonate product cannot be declared (according to my country's current chemical API application requirements).

2.2 Other classification methods:

Generally, the classification of calcium carbonate is based on the preparation process. At present, there are other classification methods in China:

According to the particle size of powder, it can be divided into conventional calcium carbonate (average particle size 5-10 microns), dimensional fine calcium carbonate (average particle size 0.1-1 microns), ultrafine calcium carbonate (average particle size not exceeding 0.1 microns, Also known as nano calcium carbonate).

According to the product use, it can be divided into industrial calcium carbonate, food additive calcium carbonate, raw material medicine calcium carbonate, etc.