Adsorption Properties of Activated Carbons Obtained from Polymer Wastes

Abstract

Non-activated carbon has been prepared by carbonizing waste products manufactured from phenol formaldehyde at 1073 K in a nitrogen atmosphere. Activated carbons were obtained by gasifying the non-activated product with air at 673 K, or with steam at 1173 K, to different levels of burn-off. The adsorption of nitrogen at 77 K and of carbon dioxide at 298 K was measured for all the carbons prepared using volumetric apparatus. The adsorption of iso-octane and α-pinene at 320 K was carried out gravimetrically using silica spring balances. The adsorption of methylene blue and of phenol from their aqueous solutions was determined spectrophotometrically. The adsorption of ammonia from its aqueous solution at 308 K was determined colorimetrically. The surface area of the activated carbons increased with increasing percentage burn-off to reach a maximum and then decreased with further increase in percentage burn-off. Gasification with oxidizing gases changed the porosity of the carbon with the change depending on the extent of gasification. The adsorption of iso-octane and α-pinene increased with increasing percentage burn-off as a result of pore widening. The low burn-off carbons obtained from phenol formaldehyde wastes are characterized by extremely high surface areas and microporosity, and a high CO/CO2 ratio on outgassing. The carbons exhibit high phenol adsorption capacities. Ammonia adsorption is favoured on carbons of a low CO/CO2 ratio.