Activated Carbons from Coal/Pitch and Polyethylene Terephthalate Blends for the Removal of Phenols from Aqueous Solutions

Abstract

Blends of two bituminous coals and a coal-tar pitch (CTP) with polyethylene terephthalate (PET) were evaluated as precursors of activated carbons (ACs). The intensity of the interactions between the raw materials, coal/CTP and PET during copyrolysis was closely observed by means of thermogravimetric analysis. In addition, the homogeneity of the carbon matrix of the chars produced at 800 °C in a horizontal oven was studied by polarized light optical microscopy. Activated carbons were prepared from single components and their blends (1:1 w/w) by subjecting them to carbonization up to 800 °C in a horizontal oven and then activation with steam at 800 °C to 50% burnoff. The porous structure of the ACs was determined by sorption of N2 at 77 K and of CO2 at 273 K. The PET-containing blends produced microporous activated carbons with a maximum BET surface area of nearly 1100 m2 g−1 and a maximum micropore size distribution of 0.6−0.8 nm in the case of the AC from the CTP/PET blend. The addition of PET to a bituminous coal was compared with the preoxidation of coal P in air as a way to reduce thermoplasticity and to promote the development of the porous structure. The modification of bituminous coals by PET appeared to be more effective than conventional coal preoxidation treatment. The resultant ACs were tested by measuring their effectiveness in removing phenols from an aqueous solution. The adsorption of p-chlorophenol (PCP) by the ACs prepared from the PET-containing blends was slightly higher than for the commercial activated carbon. The ability to adsorb PCP was found to be related to the volume of the super-micropores.