For chemical synthesis companies, pigment extraction is not rare to see. What is the easiest way to extract pigments? Molcreator today will share with you two physical methods separately using activated carbon and silica gel.
Pigment extraction methods — using activated carbon
Activated carbon is an excellent adsorbent. It has a strong adsorption capacity for pigments, bacteria, pyrogens, and other impurities, and it also has a filtering effect. There are a lot of micropores and voids inside, and the surface area can reach 200-500m2/g.
Working principle: Most pigments have a conjugated double bond structure which is easy to be adsorbed. First of all, we must understand that during decolorization there is an adsorption process, which involves pigment adsorption and product adsorption. And then is elution, which will be divided into product elution and pigment elution.
The basic factors that affect the pigment extraction using activated carbon are as follows: solvent type, amount of solvent, type of activated carbon, amount of activated carbon, temperature, and time of stirring and decolorization.
When operating pigment extraction with activated carbon, it is suggested to choose room temperature, control the amount of activated carbon at 10-30%, and then mainly screen the solvent.
Pigment extraction methods — using silica gel
Unlike activated carbon, silica gel does not have that large surface area. When carrying out pigment extraction using silica gel, there are several factors to be considered: solvent type, solvent amount, silica gel size (100-200 or 300-400), and dosage, temperature, and time of stirring and decolorization.
Under normal circumstances, it is suggested to choose room temperature, use 1-2X silica gel, and then mainly screen the solvent. The operation can refer to that of the activated carbon decolorization.
Pigment extraction methods — other thoughts
The author has made a compound once, and the operation is quite special. At that time, the decolorization effect of activated carbon was not good, and either that of the silica gel. After continuous trial and exploration, the operation was finally determined as follows: Petroleum ether was selected, though the solubility was not very good at room temperature, it was found to be completely dissolved after heating, Adding 2X silica gel, stirring at 60 degrees for 2 hours, hot filtering, washing, cooling and crystallization, after these steps, the pigment extraction result was found to be excellent.
Recently the author also did pigment extraction experiments using silica gel, and the best solvent was selected. The result of trial decolorization 3h is pretty good, basically colorless, but the effect is not as good as a small test after zooming in. The solution is to extend the time. So also consider the amplification effect.
Pigment extraction methods — summary
Decolorization actually requires a lot of work to determine the most effective operation process. You can filter all the basic conditions you need, and finally, get the most reasonable decolorization scheme.