Adsorption of polycyclic aromatic hydrocarbons by surfactant-modified clinoptilolites for landfill leachate treatment

Abstract

The authors report the potential adsorption capacities of three surfactant-modified clinoptilolites (MC)—cetylpyridinium chloride (CPC)-MC, didodecyldimethylammonium bromide (DDAB)-MC, and hexadecyltrimethylammonium bromide (HDTMA)-MC—for the removal of polycyclic aromatic hydrocarbons (PAHs) from aquatic environments and landfill leachate. A liquid–liquid extraction method was used to extract PAHs from water and GC/MS was used to analyse the PAHs. PAH accumulations on CPC-MC, DDAB-MC, and HDTMA-MC were linear over 21 successive batch adsorption tests for anthracene (708, 737, and 750 µg/g), fluoranthene (1355, 1583, and 1303 µg/g), fluorene (973, 1060, and 1147 µg/g), phenanthrene (844, 1057, and 989 µg/g), and pyrene (1343, 1569, and 1269 µg/g). The leachability after 21 successive accumulations was <2% for anthracene, <4% for fluoranthene, <3% for fluorene, <4% for pyrene, and <5% for phenanthrene for each adsorbent. PAH removals from landfill leachate for anthracene, fluoranthene, fluorene, phenanthrene, and pyrene were 97.8%, 98.6%, 95.7%, 97.0%, and 98.5% for CPC-MC and 99.0%, 99.6%, 98.0%, 99.0%, and 99.6% for DDAB-MC, respectively, meeting the fresh water quality standards established by British Columbia and the World Health Organization (WHO) for anthracene, fluoranthene, and fluorene. The molecular weight and molecular structure of PAHs and the hydrophobicity of adsorbents can fundamentally influence the PAH adsorption mechanism based on π–π stacking.