Phosphate Adsorption on Cerium/Terephthalic Acid Metal–Organic Frameworks (Ce-MOF) Driven by Effective Electrostatic Attraction and Ligand Exchange in a Wide pH Range

Graphical The pH value not only influences the surface charges of an adsorbent, but also affects the form of phosphate, which might decrease the adsorption efficiency of an adsorbent. Herein, an effective adsorbent was developed to realize phosphate adsorption by different adsorption mechanisms (electrostatic attraction or ligand exchange) in a wide pH range. Eutrophication has posed a threat to aquatic ecosystems, so it's urgent to remove excessive phosphate from water. In this study, we developed an adsorbent material, cerium/terephthalic-acid metal-organic-frameworks (Ce-MOF), to remove phosphate from different water systems. The optimal Ce-MOF presented a maximum phosphate adsorption capacity of 377.2 mg/g, approximately 3.7 times higher than that of the commercial phosphate adsorbent (Phoslock: 101.6 mg/g). Experimental and computational analysis suggested that pH dominated the adsorption process. The main forces driving the adsorption process changed from the synergistic effect of electrostatic attraction and ligand exchange at lower pH to only ligand exchange at the increased pH values. Hence, the Ce-MOF is applicable for phosphate adsorption in a wide pH range. Impressively, the adsorbent remained an excellent phosphate adsorption performance in the real water containing various interfering ions and organic matters, indicating the potential of Ce-MOF for the practical use to solve the water eutrophication issue.