Adsorption of glycerol from biodiesel washwaters

摘要

The removal of glycerol by adsorption from biodiesel washwaters has been studied at room temperature using various adsorbent materials, including activated carbons, clay minerals, and natural and synthetic zeolites. Activated carbon exhibited the best adsorption for glycerol among the examined materials. Glycerol adsorption isotherms are obtained on activated carbons after treatment under different conditions. The Langmuir isotherm coefficients and the first-order desorption kinetic parameters for glycerol on a coconut activated carbon were determined by fitting the experimental data. The adsorption of glycerol was increased by removing the functional groups from the carbon surface at high temperatures under N_2 atmosphere, and was decreased by increasing surface functional groups through HNO_3 oxidation. Compared with water, glycerol tends to adsorb more favourably on a hydrophobic carbon surface than on a hydrophilic one.