Optimization of preparation parameters for environmentally friendly attapulgite functionalized by chitosan and its adsorption properties for Cd2.

This work focused on using attapulgite and chitosan as raw materials to improve the adsorption capacity of Cd2+ from the aqueous phase by optimizing the preparation experimental parameters. The modification parameters (attapulgite-chitosan mass ratio, calcination temperature, and time) were specifically studied and optimized. The results indicated that the mass ratio of attapulgite to chitosan was 1:4, the calcination temperature was 300 °C, and the calcination time was 1 h. Both raw and functionalized attapulgite samples were characterized by nitrogen adsorption-desorption isotherms at 77 K, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and zeta potential analysis. A series of adsorption experiments showed that the pseudo-second-order kinetic model and Langmuir adsorption isotherm better corresponded with the adsorption characteristics of the newly prepared adsorbent, and the maximum adsorption amount of Cd2+ was 109.30 mg/g. Moreover, the effects of the pH value and coexisting cations on the Cd2+ adsorption in aqueous solution were investigated. Adsorption mechanism of Cd2+ on adsorbent might attribute to complexation, ion exchange reaction, and self-polarization.