A feasible strategy for separating oxyanions-loaded microfine Fe-MOF adsorbents from solution by bubble flotation

Microfine metal–organic frameworks (MOFs) are promising adsorbents for water treatment, but their commercial applicability is severely constrained by poor separability. Herein, we designed a feasible bubble flotation strategy for achieving the effective separation of oxyanions-loaded Fe-MOF particles in the solution after adsorption, by modifying the particle interface properties and introducing bubbles mineralization. The results showed that the separation of P(V), Mo(VI) and W(VI) oxyanions-loaded Fe-MOF could be completely achieved under optimum conditions. FTIR, XPS and DFT analyses revealed that the particle size and hydrophobicity of oxyanions-loaded Fe-MOF increased by sodium dodecyl sulfate (SDS) collector via chemisorption and electrostatic interactions. The collision and attachment models analysis of bubbles with particles demonstrated that the separation efficiencies of collector modified oxyanions-loaded Fe-MOFs were significantly enhanced with increasing bubble mineralization. EDLVO theoretical calculations and bubble-particle carrying ability analysis demonstrated that the gravitational interactions between oxyanions-loaded Fe-MOF particles and particles/bubbles were intensified by the collector. The gravitational interaction further induced particle aggregation and enhanced the carrying capacity of individual bubbles. This work provides a feasible strategy for the removal of oxyanions and the separation of oxyanions-loaded microfine Fe-MOF in the adsorption process.