Adsorption of phenol and chlorinated phenols from aqueous solution by tetramethylammonium- and tetramethylphosphonium-exchanged montmorillonite

Sorption of phenol and 2-, 3- and 4-chlorophenol from water by tetramethylammonium (TMA)-smectite and tetramethylphosphonium (TMP)-smectite was studied. Sorption of the phenolic compounds appeared to occur on the aluminosilicate mineral surfaces between neighboring organic cations (TMA or TMP). TMP-smectite was a better sorbent than TMA-smectite, which did not measurably adsorb any of the phenolic compounds. This disparity in sorption efficiency was attributed to differences in hydration of the interlayer cations. Apparently, hydration occurred to a greater extent in TMA-smectite that in TMP-smectite, causing the interlayer pore size to be smaller for TMA-smectite than for TMP-smectite. TMP-smectite showed selective sorption within the group of chlorinated phenols studied. Phenol and 4-chlorophenol were effectively sorbed by TMP-smectite, whereas 2- and 3-chlorophenol were not sorbed. The selectivity appeared to be size- and shape-dependent, and not strongly influenced by water solubility. (C) 1998 Elsevier Science B.V. All rights reserved.