Experimental Study on the Removal of VOCs and PAHs by Zeolites and Surfactant-Modified Zeolites

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Synthetic zeolite Na-X and clinoptilolite (Cp) as well as their modifications with quaternary ammonium salts were used to remove volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. A novel procedure was developed for the synthesis of organo-zeolites which consisted of surface modification with hexadecyltrimethylammonium bromide (HDTMA) in amounts of 1.0 and 2.0 of external cation exchange capacity (ECEC). Modification of both zeolites with HDTMA improved sorption properties. p -Xylene and dibenz[a,h]anthracene were adsorbed in amounts of 6.82 and 0.65 mg/g, respectively. Ethylbenzene and naphthalene were the lowest-removed hydrocarbons (2.99 and 0.058, respectively). The removal efficiencies for BTEX followed the order p -xylene > toluene > benzene > ethylbenzene, and for PAHs they followed the order dibenz[a,h]anthracene > benzo[a]pyrene > anthracene > naphthalene. Efficiency of sorption depends on the chemical properties of the various organic compounds (dipole moment, molar mass, molecule structure, and the time of the sorption process) and zeolites properties, like the Si/Al ratio, texture parameters, particle size, and external cation exchange capacity. The mechanism of the sorption consists of dissolving the VOCs and PAHs into the organic layer of the surfactant as well as on the penetration of organic solution into the mesopores.