Sorption of a Cationic Surfactant Benzyldimethyldodecyl Ammonium Chloride onto a Natural Zeolite

The presence of surfactants in groundwater and in drinking and superficial waters is a major public health concern. Recently, various treatment technologies have been studied to remove these pollutants; among them, the treatments based on the sorption onto natural adsorbing materials appear more eco-friendly and with very interesting removal efficiencies. The sorption of the cationic surfactant benzyldimethyldodecyl ammonium chloride (BDC-12) onto zeolitic tuff (Si/Al ratio = 2.4) was well described by a pseudo-second-order equation with a kinetic constant not depending on the exchangeable cationic form of the zeolite. The isosteric enthalpies and entropies (∆istH and ∆istS) obtained from sorption isotherms were negative, and their absolute values increased with decreasing amounts of BDC-12 bound at the equilibrium (qe). Zeolite sorbitivity (qe/unit dry mass sorbent) for BDC-12 increased with NaCl concentration in the batch solution, suggesting that the sorption process does not involve cation exchange.