Competitive adsorption of polycyclic aromatic hydrocarbons on organo-zeolites

Sorption of polycyclic aromatic hydrocarbons on organo-zeolites was investigated to determine sorbent–sorbate interaction. The hydrophobic character of the surface of the organo-zeolites was studied using in water vapor adsorption experiments. Water adsorption decreased with increasing stearyldimethylbenzylammoniumchloride (SDBAC) loading up to 75 mmol/kg, which is related to increasing sorbate hydrophobicity. With loadings above 75 mmol/kg (ECEC value), water vapor adsorption increased. Effects of adsorbent size, SDBAC loading and initial concentration of PAHs on the adsorption efficiency were also determined. The highest adsorption for the PAHs studied was achieved with OZ II 75 (OZ – organo-zeolite; II – particle size of 0.4–0.8 mm; 75 – mmol of surfactant/kg of zeolite). At a concentration of 20 μg/dm3 the adsorption index for benz[a]anthracene was 100%. The smaller adsorption indexes for PAHs with lower partition coefficients, Kow, indicated that the adsorption is primarily hydrophobic. The number of bed volumes passed through the adsorbent before the first PAH appeared in the effluent was 770. Column experiments showed competitive adsorption among the PAHs with different hydrophobicities.