Hydrothermal synthesis of mesoporous carbons for adsorption of two alkaloids

Abstract

Two mesoporous carbons were synthesized via a hydrothermal treatment approach, characterized and evaluated for adsorption properties of berberine hydrochloride and matrine from water. The mesoporous carbons have BET specific surface areas of 1568.1 and 769.3 m2/g, pore volumes of 1.44 and 0.89 cm3/g, average pore diameters of 3.75 and 8.22 nm, and few O-containing functional groups on the surfaces. Both the mesoporous carbon adsorbents can effectively adsorb berberine hydrochloride and matrine from aqueous solutions, the higher equilibrium adsorption capacities of berberine hydrochloride and matrine at 298 K are 385, and 275 mg/g at 0.10 mg/mL, respectively. Adsorption enthalpy, entropy and free energy of berberine hydrochloride and matrine on the selected mesoporous carbon (with higher BET specific surface area and pore volume) were calculated. The adsorption of berberine hydrochloride and matrine on the selected carbon sample is fast at 298 K, 95% of the adsorption equilibrium could be achieved within 180 and 120 min, respectively. The dynamic adsorption capacities on the selected adsorbent are calculated to be 343.1 and 383.4 mg/g for berberine hydrochloride and matrine, respectively; and 70.8% of the adsorbed berberine hydrochloride and 79.2% of the adsorbed matrine could be desorbed by a 70% alcohol solution. These results provide a reference to the large-scale industrial production and application of mesoporous carbons as potential adsorbents in purification of alkaloids from herbal plant extracts.