Sorption of rutin and tannin on active carbon BAU-A
Natural phenolic compounds (NPC) are the most important biologically active additives (BAA) and a part of drugs, biologically active additives (BAA) and water-ethanol extracts. AC BAU-A was used to isolate NPC from aqueous-alcoholic extracts. The purpose of this research is to study the adsorption and desorption capacity of NPC (for example, rutin and tannin) on the active carbon BAU-A. The adsorption of NPC was carried out from solutions of standard samples and the resulting water-ethanol extracts on the ultrasonic unit on active carbon (AC) BAU-U with the particle size of 1.0-3.5 mm. It was experimentally proved that the carbon fraction with the particle size 1.0-1.5 mm most fully adsorbs the studied NPC (93-95%) during 15-30 minutes. The obtained adsorption isotherms of NPC on BAU-A belong to the L-type according to the Gibbs classification and confirm the physical mechanism of adsorption. The adsorption isotherms were used to calculate the physicochemical parameters using the theory of monomolecular adsorption (Freindlich, Langmuir equations), polymolecular adsorption (BET model), and the theory of volume filling of micropores (Dubinin-Radushkevich equation). The obtained values of the Gibbs energy confirm that natural phenolic compounds are adsorbed in micropores due to van der Waals forces, and the surface functional groups of the AC form hydrogen bonds of the sorbate-sorbent. The desorption of NPC was carried out under dynamic conditions in a column 360 mm long, 15 mm in diameter, and an AC layer height of 80 mm. Polar individual solvents (water, methanol), an aqueous solution of HCl, and a binary mixture of water and ethanol (φ<sub>2</sub> = 0.47) were used as eluting solutions. The most effective eluting solution for isolating (75-80%) NPC from the sorbent is methanol or a water-ethanol binary mixture. Thus, on the basis of the obtained experimental data, it was shown that AC BAU-A has a high adsorption capacity with respect to NPC. The use of a binary mixture of water-ethanol or methanol as an eluting solution makes it possible to isolate almost 80% of NPC from the BAU-A sorbent (in terms of rutin and tannin). Active carbon BAU-A manufactured according to GOST 6217-74 (OA ENPO "Neorganika", Elektrostal, Moscow region) is recommended for adsorption of NPC from water-ethanol extracts with subsequent desorption.