adsorption of cr(vi) from aqueous environment onto metal-organic framework mof-808: synthesis, kinetics, equilibrium and thermodynamics

Unlike the removal of organic contaminants from aqueous solution, heavy metals are not easily degraded and remain a persistent threat to the environment [1]. the cr (vi), as one of the heavy metals is one kind of dangerous water pollutants authenticated by the world health organization (who) [2]. in recent years, numerous techniques have been developed for the removal of cr(vi) from aqueous solution. among various developed techniques for cr(vi) removal, adsorption has attracted more attention due to its high efficiency, simplicity, low energy consumption and easy recyclability [3]. metal organic framework (mof) has received extensive attention due to its unique crystal structures and excellent properties [4]. in the present study, we have successfully synthesized water-stable mof-808 material, which was developed into an effective cr(vi) removal material from water. the experimental results suggest that mof-808 fast response and high capture capability for cr(vi). the maximum absorption capacity of mof-808 at 298 k and ph = 5 was 280 mg/g for cr(vi) and adsorption equilibrium was reached after 20 min. pseudo-second-order kinetic (r2 = 0.9945) and langmuir isotherm model (r2 = 0.9995) are more suitable for describing the adsorption process of cr(vi) on mof-808, which indicates that the process is a physically controlled monolayer adsorption. thermodynamic investigation proposed spontaneous (δg° < 0), disordered (δs° > 0) and endothermic (δh° > 0) for adsorption process. besides, mof-808 displayed an appropriate reusability for the elimination of cr(vi) ions from their aqueous solutions for 6 successive cycles. in general, mof-808 has been shown well adsorption properties and reusability, and our finding might provide a new idea for developing efficient and reusable adsorbent to remove cr(vi) from wastewater.