Preparation of activated charcoal from Acrocomia aculeata for purification of pretreated crude glycerol

Activated charcoal was prepared from Acrocomia aculeata (macauba) endocarp by ZnCl2 activation and then used for the adsorptive purification of pretreated crude glycerol (CG) containing pigments, such as beta-carotene. The pretreatment of glycerol involved filtration of the K3PO4 formed by the addition of H3PO4 to the crude glycerol containing KOH. A mixture of 1.38:1 w/w of ZnCl2:Acrocomia aculeata pulp was heated at 120 degrees C with stirring for 24 h. The mixture was activated by heating at 600 degrees C for 3 h. The activated charcoal was cooled to 25 degrees C, washed with a 1:1 mixture of methanol and water (100 mL) and heated at 150 degrees C for 2 h. The surface properties of the activated charcoal (surface area 627 m(2) g(-1), pore volume 0.39 m(3) g(-1), Bronsted sites 118.23 mu mol g(-1), and Lewis sites 104.86 mu mol g(-1)) and the adsorption capacity for impurities in H3PO4-pretreated crude glycerol were investigated. The activated charcoal exhibited the most suitable surface properties for the purification of pretreated crude glycerol, attaining a 95.99% glycerol concentration (by GC) using 10 g/L with gravity filtration through a column at room temperature over a 48-h period. The purified glycerol was characterized by GC/MS, H-1- and C-13-NMR, and DSC and TG analyses. The activated charcoal was regenerated by washing with methanol and hexane and heating to 150 degrees C for 5 h. The activated charcoal could be re-used three times to remove all of the pigments before it was necessary to re-activate the charcoal by heating with ZnCl2.

Automated summary

Activated charcoal prepared by ZnCl2 activation can be used for the adsorptive purification of pretreated glycerol. The surface properties of the activated charcoal are suitable for increasing glycerol concentration effectively through gravity filtration at room temperature. The activated charcoal can be regenerated through washing and heating treatment for reuse.