Color redness problem in white solid products
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Dear experts: Our company has a product that is obtained by reacting two solutions to form a precipitation. The reaction kettle is an enamel kettle. This product is normally a white solid. In the reaction, calcium ions need to be removed first, so liquid caustic soda is added to the system and then EDTA is added to complex calcium ions. The amount added is 100% excess according to the theoretical calcium content. ； But during the liquid separation, it was found that the precipitated product was red. Of course, the color was not very dark. Now I want to ask you guys: Is the redness caused by excess EDTA? Or is it possible that it is caused by the enamel reactor? Or maybe it's caused by organic matter contained in the system?
There is no specific reaction situation and it is difficult to analyze. It is unlikely to be the cause of the ceramic reactor.
It may be due to the presence of organic matter. If the EDTA is too high, you can confirm by doing a few more sets of data!
It is impossible for EDTA to let the material turn red, and it is even more impossible for the glass-lined kettle. The most likely reason is that there are other impurities in the product. It is recommended to further characterize it!
Spend some money to do an elemental analysis. It may be impurities brought in by liquid alkali, such as iron.
It may be that the organic matter or other impurities brought in reflect the color of the by-products produced. . . . It is best to further characterize pure substances and colored substances. . Look at the difference between the two, do more instrumental analysis to conduct functional group identification, mass spectrometry, etc., and finally you should be able to draw a conclusion. . . . .
Is it possible that EDTA forms complexes with other substances?
Liquid caustic soda? Is it sodium hydroxide solution? Or other types of strong alkali? If it is a strong alkali, you should consider that the strong alkali may react with the enamel!
Enamel kettles are not suitable for use with strong alkali. Liquid alkali can easily cause the enamel kettle to explode.