Sorption of p-nitrophenol by anion-cation modified palygorskite

A series of anion-cation modified palygorskites were prepared by microwave irradiation, and characterized with FT-IR. Compared with natural palygorskite, the p-nitrophenol sorption capacity with anion-cation modified palygorskite was significantly improved. The maximum sorption capacity (137.74 mg g-1) was obtained with the mass ratio 1:4 and 3:10 of hexadecyltrimethylammonium bromide to sodium dodecyl sulfate and the surfactant to palygorskite of at 313 K. The sorption equilibrium was in accordance with the Langmuir isothermal sorption equations. Thermodynamic function calculated showed that the sorption was a spontaneous and exothermic process. Free energy of the sorption increased with the increase of the temperature. The sorption of p-nitrophenol followed the pseudo-second-order process (sorption rate constant: 0.00453 mg-1 min-1).