C@TiO₂ core-shell adsorbents for efficient rhodamine B adsorption from aqueous solution

In the present work, C@TiO₂ core-shell adsorbents were successfully prepared and the adsorption capacities for rhodamine B (RB) were investigated at different conditions. The adsorbents were prepared by first in-situ hydrolysis and deposition of TBOT on the surface of ZIF-8 nanoparticles to obtain ZIF-8@titania gel, and then carbonization. XRD, SEM, TEM, and N₂ adsorption-desorption techniques were employed to characterize the adsorbents. The results showed that the adsorbents were comprised of TiO₂ shell and carbon core. Large surface area and hierarchical pores, which were different from ZIF-8 derived porous carbon, were generated due to the less contraction of carbon during carbonization when robust TiO₂ shell covered on the surface. The highest adsorption capacity for RB was 298 mg/g on C@TiO₂. Apart from the hierarchical pores and large surface area, the low surface charge of C@TiO₂ core-shell adsorbents was also observed, which also contributed to the high adsorption capacity for cationic dyes. The reuse experiments showed that the adsorbents maintained the high adsorption capacity after 5 cycles. The high stability is crucial for practical application.