Sorption of 2,4,6-trichlorophenol in model humic acid-clay systems

Humic acids and clays are important soil components that influence the sorption and desorption of organic contaminants; however, it is unclear how humic acids influence the sorption of organic contaminants onto clays and their subsequent desorption. Sorption and desorption of 2,4,6-trichlorophenol (2,4,6-TCP) by and from humic acid-modified K+- and Ca2+-montmorillonite and -illite were compared with unmodified clays using batch equilibration methods. Commercial humic acid and the humic acid extracted from forest soil were employed in this experiment. The adsorbed amount of 2,4,6-TCP by commercial humic acid was almost twice as large as that adsorbed by the extracted soil humic acid. More 2,4,6-TCP was sorbed onto K+- and Ca2+-illite than onto K+- and Ca2+-montmorillonite. K+ clays were more effective in adsorbing 2,4,6-TCP than Ca2+ clays. Sorption of 2,4,6-TCP on humic acid-modified Ca2+- and K+-montmorillonite and -illite increased as compared with unmodified clays. The sorption nonlinearity of 2,4,6-TC...