Rapid adsorption and enhanced removal of emodin and physcion by nano zirconium carbide.

In this study, nano zirconium carbide (n-ZrC) was synthesized by preceramic polymers method, and it was used to adsorb emodin and physcion from solutions for the first time. The prepared material was characterized by various technologies. The adsorption experiment was carried out to investigate the emodin and physcion removal performance. The results indicate that the pseudo-second-order kinetic model and the Langmuir model correlated satisfactorily to the experimental data, and the thermodynamic parameters are also calculated. Especially, n-ZrC can remove >95% of emodin or physcion in a minute under the optimal conditions, it is the fastest adsorption rate compared to other commonly used adsorbents (commercial zirconium carbide, activated carbon, C18, PSA, GCB and florisil). The adsorption mechanism was discussed, which suggests that Van der Waals' forces are the primary driving power during the adsorption process. Moreover, n-ZrC is stable at different pH and it can be reused at least fifteen times.