Glycerin waste as sustainable precursor for activated carbon production: Adsorption properties and application in supercapacitors

Crude glycerin is one of the main residue largely generated in the biodiesel industry, and was used without purification as precursor for the synthesis of activated carbons (AC). The glycerin polymerization (under reflux with H2SO4) was a crucial step required before the chemical activation process (using ZnCl2 or H3PO4). Several AC synthesis conditions were investigated such as the type of activating agent (ZnCl2 or H3PO4), the impregnation ratio, activation time and temperature. The glycerin ACs demonstrated potential application as supercapacitor electrode (specific capacitance of the device up to 15.5 F g(-1) at a current density of 0.25 A g(-1) with high rate capability and cyclability) and for the adsorption of organic contaminants from water: the paracetamol drug (PC) and the methylene blue dye (MB). The AC adsorption capacities were mostly related to the carbon surface areas and acidity. The Langmuir adsorption capacity towards MB reached 370 mg g(-1) and 88 mg g(-1) for the paracetamol drug. These findings indicate that the crude glycerin waste can be used directly as sustainable precursor for the preparation of high quality activated carbons.