Performance and mechanisms of sodium dodecyl benzene sulfonate-modified maifanite for Cr(VI) and Cd(II) removal from aqueous solution

Maifanite modified by the anionic surfactant sodium dodecyl benzene sulfonate was prepared using a wet method in order to improve the removal performance of Cr(VI) and Cd(II) from aqueous solution. Analyses of scanning electron microscope, energy-dispersive spectroscopy, X-ray diffraction and Fourier transform infrared spectra showed that sodium dodecyl benzene sulfonate had been successfully attached to the surface of maifanite and the adsorbent introduced new functional groups (sulfonate group) that could adsorb metal ions. At the dosage of 0.10 g of adsorbent, pH 6 and 298 K, the maximum adsorption capacities of the modified adsorbent for Cr(VI) and Cd(II) were 84.03 and 94.34 mg/g, respectively, displaying a higher efficiency for the removal of Cr(VI) and Cd(II). The removal process was not only less pH dependent, affected by coexisting ions to a small degree, but also had good renewable properties. The Langmuir model fit the experimental data better than the Freundlich model and the quasi-second-order model described well the kinetic data, which indicated the presence of chemical adsorption. Further analysis showed that the removal of Cr(VI) and Cd(II) was accomplished mainly via surface complexation and electrostatic interaction. In brief, sodium dodecyl benzene sulfonate-modified maifanite was a very promising adsorbent owing to the large adsorption capacities and convenient application.