Sorption studies of chloroanilines on kaolinite and montmorillonite

Batch experiments have been performed in order to evaluate the ability of the two reference clays kaolinite (KGa-1) and Na-montmorillonite (SWy-1) to retain three representative chloroanilines: 3-chloroaniline, 3,4-dichloroaniline and 2,4,6-trichloroaniline. Systems containing the clay mineral and the pollutant solution (at concentration levels ranging between 1.0 and 10.0 mg/L) were considered and RP-HPLC methods were employed to follow the sorption processes as a function of time. The results indicate that montmorillonite shows a general higher sorption capacity with respect to kaolinite and that for both the reference clays, in the concentration range investigated, the amount of pollutant sorbed increases with concentration. The sorption coefficient Kd ranges between 0.0030 L/g for the system 3-chloroaniline–kaolinite and 0.0488 L/g for the system 2,4,6-trichloroaniline–montmorrillonite. The most lipophilic trichloroaniline shows the greater sorption. X-ray analyses suggest for kaolinite a preferential sorption onto the mineral surface, while for montmorillonite a progressive swelling of the structure is observed, likely due to sorption processes that also take place in the interlayer.