Manufacturing Process of Cadmium Red Pigmnet

The industrial production of general-purpose cadmium red commonly used three methods: calcining method, precipitation-calcining method and hydrothermal method.
1. Calcining method
The calcining method uses cadmium carbonate, sulfur and selenium as starting materials and directly calcined to produce cadmium red. Put the raw materials in a mixing barrel with a stirrer or a grinder to mix evenly, and put them into a converter or a muffle furnace for calcination. The ratio of the charge and the calcination temperature determine the hue and characteristics of cadmium red.
Cadmium Red Pigmnet
2. Precipitation-calcination method
First, cadmium salt (CdCO3) is reacted with sodium sulphur selenide solution to produce cadmium sulphur selenide (nCdS•CdSe) precipitate, and then the precipitate is calcined at high temperature to produce cadmium red. The calcination method is similar to the above-mentioned calcination method. According to different starting materials for the manufacture of cadmium red, the precipitation-calcination method can be divided into insoluble cadmium salt method (such as cadmium carbonate method) and easily soluble cadmium salt method (such as cadmium sulfate method).

3. Hydrothermal method
  The hydrothermal method is divided into two steps. The first step is the same as the precipitation reaction process in the above precipitation-calcination method, that is, cadmium carbonate is used to react with sodium sulfur selenide solution in a liquid phase of 60 to 90 °C to generate cadmium sulfur selenide precipitation. The second step is the crystallization conversion process. The amorphous semi-finished product is converted into crystalline pigment by hydrothermal method, that is, the precipitate synthesized in the first step is heated to boiling (90~160°C) in the reactor, and reacted for 1~2 hours , And then quench the slurry with cold water (5~15°C) to obtain cadmium red pigment, which is finished by decantation, filtration, drying and crushing.
Finally, it needs to be explained that ironware is prohibited in the process of making cadmium red pigment. Hunan Nolifrit produces and supplies high-quality cadmium red for global customers. The finished cadmium red pigment has been exported to many countries around the world and is trusted by customers. If you are looking for a supplier of cadmium red pigments, please contact us for free samples. For more information, please call us.