Removal of pharmaceutical and dye compounds from aqueous solution by nanostructured metal-organic framework based MIL-53 (Fe)

Abstract

Introduction: The main approach in this research is the synthesis and investigation of materials based on the metal-organic framework MIL-53(Fe) in the field of water treatment and improving their properties and features by modifying and compositing with other materials and finally their use in the pollutant removal systems.

Method: Initially, MIL-53(Fe) was synthesized via a hydrothermal method. Three varying amounts of precursors and solvent were used to prepare this framework which is denoted as MIL-53A, MIL-53B, and MIL-53C. All as-synthesized samples were modified with different amounts of APTMS. Also, the Surface functionalized Metal-Organic Framework and Biological Macromolecule (SFMOF/BM) as an eco-friendly biocomposite was synthesized. Chitosan was used as a linear polysaccharide and biological macromolecule. The properties of synthesized adsorbents were surveyed by various techniques containing XRD, FESEM, TEM, EDX, BET, TGA, FTIR, and Raman analyses. Adsorption experiments were carried out to rationalize the differences in behavior and efficiency of the synthesized adsorbents in removing organic pollutants using Metronidazole (MNZ), tetracycline (TC), and Direct Red 23 (DR23) as model pollutants. The ideal conditions for maximum DR23 removal from aqueous solutions were studied and optimized. In addition, adsorption kinetics and isotherm models were obtained and discussed. Finally, the reusability of the adsorbents was investigated through the regeneration of the saturated adsorbents

Results: According to the presented results, it was observed that the adsorption capacity of pure MIL-53(Fe) is noticeably different from each other. Also, surface modification with an amine functional group significantly improved the adsorption efficiency. SFMOF/BM adsorbent displayed remarkable performances in adsorption capacity and removal efficiency among all the synthesized adsorbents in this study. The data clearly showed that the adsorption is pH-sensitive, signifying that electrostatic interaction is the dominant adsorption mechanism. In addition, the other interactive forces viz. H-bonding and π-π interaction may further explain the DR23 adsorption on MOFs. The Langmuir isotherm and PSO kinetics were best fitted for the experimental data. The SFMOF/BM biocomposite with adsorption capacities of 12,500 exhibited the highest adsorption capacity among all samples. The high reusability and stability of SFMOF/BM even after five cycles adds to its advantage as a robust adsorbent material.

Conclusion: Because of the high adsorption capacity, easy regeneration of the saturated adsorbent, and its reusability, it can be concluded that the developed SFMOF/BM biocomposite adsorbent could be considered a promising novel adsorbent for water treatment applications to remove organic pollutants (dye and pharmaceuticals).