Tuning adsorption capacity of metal–organic frameworks with Al3+ for phosphorus removal: Kinetics, isotherm and regeneration

The separation and recycling of phosphate from sewage are indispensable to be explored due to eutrophication and phosphorus deficiency. Herein, iron-aluminum metal organic framework (Fe-Al-MOF) was successfully synthesized via solvothermal one-step treatment. The Fe-Al-MOF was measured using scanning electron microscopy (SEM), infrared spectrometry (IR), thermogravimetric analysis (TGA) and X-ray powder diffractometer (XRD). Fe-Al-MOF was selected to explore phosphate adsorption performance and its mechanism. The results showed that Fe-Al-MOF adsorbent demonstrated an excellent phosphate sorption capacity of 38.33 mg P/L, strong interference immunity in the presence of co-existing ions and optimal pH adapted to real wastewater. The experimental data was in accordance with the Langmuir model and the pseudo-second-order model, indicating monolayer adsorption as well as physical and chemical adsorption. More importantly, Fe-Al-MOF could reserve over 80% after four continuous regeneration cycles in comparison with the first adsorption capacity, showing its economics. A series of characterizations declared that chemical adsorption, ligand exchange and electrostatic attraction were main adsorption mechanisms by Fe-Al-MOF. Overall, Fe-Al-MOF has high stability, good reusability and high economy to apply for controlling wastewater and eutrophication.