Sorption study of 2,4-dichlorophenol on organoclays constructed for soil bioremediation

The role of the type and amount of cationic surfactant in the sorption behaviour of partially modified clays was studied and the applicability of a partially modified organoclay for bioremediation was demonstrated. Partially modified surfactant/clay complexes (“organoclays”) were prepared from Na-montmorillonite by using monoalkyl-(dodecyltrimethylammonium and octadecyltrimethylammonium) and dialkylammonium (didodecyldimethylammonium and dioctadecyldimethylammonium) bromides. The degree of modification was varied between 35 and 89% of the cation exchange capacity of montmorillonite (MM). The sorption of 2,4-dichlorophenol (DCP) on organoclays was studied by using the batch technique. The intercalation of DCP into the interlayers of organo-MM was detected by X-ray diffraction. sorption isotherms found were non-linear indicating that the sorption is not only based on a simple partition mechanism. The adsorption coefficients Kd calculated from the initial isotherm slope turned out to be exponential with the organic carbon content of organo-MM (foc). In particular, dialkylammonium-modified MM revealed outstanding sorption characteristics for DCP. The comparison of partially modified organo-MMs with similar foc and volume fraction of surfactant indicated that the surfactant arrangement in the interlayers significantly influences the DCP adsorption. It could be assumed that both the kind and degree of exchanged surfactant play a decisive role in the adsorption of DCP on the organoclays. By performing biodegradation experiments in the presence of dioctadecyldimethylammonium montmorillonite, the complete biodegradation of DCP was achieved demonstrating the applicability of partially modified organoclays for bioremediation.