Ultrarapid and Sustainable Synthesis of Trimetallic-Based MOF (CrNiFe-MOF) from Stainless Steel and Disodium Terephthalate-Derived PET Wastes

Abstract

Designing easy and sustainable strategies for the synthesis of metal−organic frameworks (MOFs) from organic and inorganic wastes with the efficient removal of phosphate from water remains a challenge. The majority of the reported works have utilized costly precursors and nonsoluble ligands for the synthesis of MOFs. Herein, we have developed a low-cost, simple, and sustainable alternative approach using the coprecipitation method in water at room temperature for the synthesis of a new adsorbentbased trimetallic MOF. Poly(ethylene terephthalate) and stainless steel wastes were used as sources of water-soluble disodium terephthalate ligand and three metallic species (chromium, nickel, and iron salts) for the fabrication of trimetallic MOF (CrNiFe-MOF), respectively. The newly developed MOF demonstrates a superior space-time yield of 5760 g m −3 day −1 , reaching a level allowing the industrialization production of this sustainable MOF. The scanning electron microscopy and adsorption studies revealed that the developed trimetallic MOF consists of aggregated nanoparticles and the presence of defective as well as mesoporous structures. This MOF showed an enhanced adsorption capacity of phosphate from real eutrophic water samples and higher stability in a range of pHs. The density functional theory calculations evidenced that the phosphate ions preferentially adsorb over H 2 O toward the metal oxo-trimers, with the adsorption energies increasing from H 3 PO 4 to PO 4 3− species in line with an improvement of the adsorption performance of CrNiFe-MOF when the pH increases, i.e., when HPO 4 2− and PO 4 3− become more predominant. These calculations also supported that the incorporation of Cr metal sites in the oxo-trimer is expected to boost the phosphate affinity of the MOF. Finally, our work provides an easy and eco-friendly approach for MOF designing to enhance phosphate removal from water.

Sustainable and shaped synthesis of MOF composites using PET waste for efficient phosphate removal

“…PET hydrolysis was performed under alkaline conditions following our published work. 24 The bottles were washed and rinsed with water and ethanol and then dried. PET flakes were obtained by cutting the bottles into 5 Â 5 mm-sized pieces.…”