Open Access Conference Proceedings

Chars and carbon membranes were prepared from fresh and smoked cigarette filters, and used as adsorbents for clofibric acid removal. Carbonization of cigarette filters took place at 650, 750 and 900 °C, whereas membranes were synthesized by filter dissolution in acetone, using NaCl (porogen) and glycerol (plasticizer). Acid mediated carbonization (225 and 250 °C) of the membranes was performed. Solution pH was monitored throughout the adsorption experiments. The chars are basic powders with apparent surface areas up to 494 m2 g-1 and a porosity composed by supermicropores (0.7-2 nm wide) and mesopores (2-50 nm wide), allowing clofibric acid (critical dimension 0.6 nm) to access all adsorption sites. Carbonization of smoked filters promoted higher porosity levels and SEM analysis showed that a more extensive carbonization occurred in the outer surface of the chars particles. The presence of TiO2 particles was confirmed in all the chars. Pores were homogeneously created at the membranes surface. Acidic carbon membranes (pHPZC ≈ 3.7) were obtained with different degrees of porosity, proportional to the pyrolysis temperature. Both forms of clofibric acid (protonated and deprotonated) were readily adsorbed onto the carbon materials, with exception of the chars prepared at 900 °C, which adsorbed predominantly the deprotonated form. In equilibrium, an inverse correlation between solution pH and concentration of the pollutant was observed, and higher uptakes were observed for experiments with solution pH values above 5, suggesting that adsorption of the neutral species contributed significantly to the overall removal.

Keywords: Cigarette filters, chars, carbon membranes, adsorption, clofibric acid

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