Highly Porous MOF Adsorbent for Wastewater Treatment

Abstract

Heavy metal detoxification is one of the major challenges in our generation.Metals such as Cu(II), Pb(II) and Ni(II) have a toxic effect to human health.Therefore, it is necessary to eliminate such metal ions from aqueous solutions.In this study, we report a newly developed cadmium metal organic framework (MOF) adsorbent for Cu(II), Pb(II) and Ni(II); namely cadmium benzene 1,2,4,5-tetracarboxylate (Cd-H4bta MOF).This material was synthesized by refluxing; benzene 1,2,4,5-tetracarboxylic acid (H4bta) was reacted with cadmium salt in dimethylformamide medium.The produced material was characterized by scanning electron microscopy, nitrogen adsorptiondesorption analysis, thermogravimetric analyzer, X-ray diffraction and Fourier transformed infrared spectroscopy.Scanning electron microscopy images revealed that the highly porous rhombic prism crystals of variable sizes were synthesized and its morphology is reported for cadmium coordination compounds.TGA-DTA profiles showed the thermal behaviour of this material to be highly stable.Our proposed adsorbent material i.e., Cd-H4bta MOF consist of cadmium ions.Before use Cd-H4bta MOF stability test in aqueous solution was conducted and it was found the material is insoluble and does not leach cadmium ions, therefore it is suitable and safe for aqueous solution use.Its adsorption capabilities to remove Cu(II), Pb(II) and Ni(II) ions from aqueous solutions were investigated using batch experiments by varying parameters such as initial concentration of metal ions and contact time; thereafter isotherms and kinetics were determined.The metal ions measurements before and after adsorption were carried out through atomic absorption spectroscopy.The Cd-H4bta MOF adsorption capacities for Cu(II), Pb(II) and Ni(II); were 183.43, 171.42 and 120.31 mg/g respectively.Kinetics data of all targeted metals, followed pseudo second order model.The results indicated that Cd-H4bta MOF is a promising adsorbent for Cu(II), Pb(II) and Ni(II) ions in aqueous media