Gadolinium(III) terephthalate metal-organic framework for rapid sequestration of phosphate in 10 min: Material development and adsorption study

Phosphorus with concentration above a few ppm in waters can easily cause eutrophication and poor water quality (e.g. algal blooming). In this study, we synthesized a non-porous gadolinium terephthalic acid (Gd-PTA) metal-organic framework (MOF) for efficient and rapid removal of phosphorus. Gd-PTA was prepared with gadolinium as the core metal center and terephthalic acid as the organic ligand, by which a well defined structure of new MOF was established. The adsorption isotherm and kinetics were well described by Langmuir isotherm equation and the intraparticle surface diffusion model, respectively. The maximum adsorption capacity was as high as 206.13- PO 4 3 − mg/g, which outperforms many reported and/or commercially available adsorbents (normmaly 5–150  PO 4 3 − mg/g). The adsorption was completed at the end of 10-min contact time, much faster than many reported adsorbents for uptake of anions (normmaly hours to days). The MOF performed very well in the uptake in phosphate containing solution with initial pH 3 to 9 and ionic strength (NaNO 3 ) of 0–1 M, and in the presences of competiting sulphate, nitrate, carbonate and humic acid (each with 30, 50, and 100 mg/L). The absorption of phosphate was mainly controlled by ion exchange between phosphate and organic ligand of MOF as well as the interaction between unsaturated metal center of coordination and phosphate. This study demonstrates that the newly developed MOF reported here is a promising adsorbent for cost-effective treatment of phosphorus in water and wastewater.