Adsorption and mechanistic study for phosphate removal by magnetic Fe3O4-doped spent FCC catalysts adsorbent

The waste materials utilization has attained increasing attention due to the generation of a large number of spent materials. In the current study, a practical magnetic adsorbent (Fe3O4-doped spent Fluid Catalytic Cracking catalysts, abbreviated as FCCx@(Fe)y-O) was prepared, liable to be separated. The batch experiments were employed to investigate the phosphate removal behavior. The findings of this study demonstrated that FCC4@(Fe)1-O exhibited the best phosphate removal performance among the adsorbents (FCCx@(Fe)y-O), attributed to rough surface layer, i.e., composed of active sites. The various characterizations results revealed that the adsorption behavior of FCC4@(Fe)1-O followed the inner-sphere adsorption based on ligand exchanges mechanism. Furthermore, OH− played an important role in the adsorption process. Minor effects were showed on the phosphate removal in the experiments of commonly coexisting anions, except CO32− and SiO32−. The above findings affirmed that FCC4@(Fe)1-O was a suitable adsorbent for phosphate removal in the practical application. [Display omitted] •Magnetic adsorbents were prepared with spent FCC catalysts based on waste utilization.•FCC4@(Fe)1-O could efficiently remove phosphate with extensive range of pH.•FCC4@(Fe)1-O quickly separated from the aqueous solution, shorter than 2 min.•The underlying mechanism was inner-sphere complexation based on ligand exchange.