Tuning the morphology and adsorption capacity of Al-MIL-101 analogues with Fe3+ for phosphorus removal from water

In this work, water-stable Al-MIL-101 analogues were successfully synthesized by adjusting the Fe/Al ratio to obtain excellent phosphorus removal efficiencies. The introduction of Fe3+ into the precursor solution allowed the final structure of aluminum metal-organic frameworks (Al-MOFs) to be tuned without introducing Fe into the final structure. The formation of Al-MIL-101 analogues with different morphologies and surface areas was accomplished by adjusting the Fe/Al molar ratio in the precursor solution. Compared with pure Fe-MIL-101 or Al-MIL-101, Al-MIL-101 analogues exhibited ultra-fast phosphorous adsorption kinetics and high phosphorous adsorption capacities. Al-MIL-101, produced with an Fe/Al feed molar ratio of 0.5, achieved a maximum phosphorus uptake capacity of 90 mg P/g, which is much higher than the phosphorus absorption reported in most literatures. More importantly, the Al-MIL-101 analogue obtained using an Fe/Al molar ratio of 0.5 exhibited an excellent phosphorus removal efficiency, even after multiple adsorption/desorption cycles. These results indicate that Al-MOFs produced by adjusting the Fe amount in the precursor solution are promising candidates for the removal of phosphate from water.