Preparation of new MOF-808/chitosan composite for Cr(VI) adsorption from aqueous solution: Experimental and DFT study

In this study, a series of Zirconium-based MOF and chitosan composites (MOF-808/chitosan) were synthesized as efficient adsorbent for Cr(VI) ions elimination from aqueous solution. MOF-808/chitosan structure and morphology was characterized by FE-SEM, EDX, XRD, BET, zeta potential analysis, FT-IR, XPS techniques. The kinetic studies ascertained that Cr(VI) adsorption over MOF-808/chitosan followed pseudo-second-order kinetic model. The adsorption isotherms fitted the Langmuir isotherm model, implying on homogeneously adsorption of Cr(VI) on the surface of MOF-808/chitosan. According to the Langmuir model, the maximum capacity was obtained to be 320.0 mg/g at pH 5. Thermodynamic investigation proposed spontaneous (Delta G degrees < 0), disordered (Delta S degrees > 0) and endothermic (Delta H degrees > 0) for adsorption process. Besides, MOF-808/chitosan displayed an appropriate reusability for the elimination of Cr(VI) ions from their aqueous solutions for six successive cycles. DFT study of the adsorption process displayed and confirmed the role of hydrogen bonding and electrostatic attraction simultaneously.

Automated summary

In this study, Zirconium-based MOF and chitosan composites were synthesized as efficient adsorbents for removing Cr(VI) ions from aqueous solution. The structure and morphology of MOF-808/chitosan were characterized, and the adsorption process was found to follow pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic investigation indicated that the adsorption process was spontaneous, disordered, and endothermic. The DFT study confirmed the role of hydrogen bonding and electrostatic attraction in the adsorption process.