Ice-templated porous polymer/UiO-66 monolith for Congo Red adsorptive removal

Chitosan/MOF composite porous monolith used in water remediation as adsorbent can realize high-efficient removal of pollutant in water and facile recycling from water. However, dissolution of chitosan (without crosslinking) in acidic aqueous solution will cause breakage of composite monolith. Herein, we report a chitosan/UiO-66 monolith prepared by ice-templating method. Specially, a pre-crosslinking treatment (by glutaraldehyde) is employed before the monolith formation, which obviously boosts its stability in aqueous solution. The composite monolith is evaluated by SEM, N 2 adsorption, XRD, and batch adsorption tests for Congo Red (CR). The results show that the composite monolith possesses a typical ice-templating structure with hierarchical (mirco- / meso- and macro-) pores. UiO-66 particles are embedded on the surface of chitosan matrix, and the crystal structure of UiO-66 is not changed obviously by the crosslinking and freezing process. The composite monolith exhibits high adsorption efficiency (90% of CR was removed from its aqueous solution in 60 min) and the maximum adsorption capacity of 246.21 mg/g (derived from Langmuir model) can be reached. After adsorption, the monolith is collected by a facile procedure and recovered using ethanol for evaluating its reusability. After 4 cycles, the CR removal efficiency of the composite monolith still remains ~90% of the initial efficiency. This work demonstrates that the simple crosslinking procedure before monolith formation can ensure the intact shape of the chitosan/MOF monolith during adsorption.