Efficient removal of Co(II) from aqueous solution by flexible metal-organic framework membranes

In this work, flexible surface-supported metal-organic framework (MOF) membranes were successfully prepared on fabric by a simple method and used for cobalt adsorption for the first time. MIL-101-NH2 crystals were deposited in-situ on the fabric by hydrothermal synthesis. SEM and XRD results demonstrated that the MOF membranes were robust, stable, and consistent. The influences of pH, temperature, and initial cobalt concentration on the cobalt adsorption capacity of the membranes were investigated. The maximum Co(II) adsorption capacity was found to be 116.3 mg g−1, and the MOF membranes retained excellent adsorption capacity even after ten cycles. The Co(II) adsorption process on the membranes was endothermic and spontaneous and followed pseudo-second-order chemisorption. The XPS analysis implied that the formation of Co2+ and -NH2 complexes dominated the cobalt adsorption process. The application of MOF membranes in Co(II) adsorption simplified the MOF powder recycling process indicating that the easily-prepared and environment friendly flexible MOF membranes have a great potential for engineering applications in cobalt adsorption.