Hierarchically porous carbon derived from pore remodeling of waste polymeric membranes for high-efficiency adsorption applications

Abstract

It is extremely significant but technically challenging to construct a hierarchically porous carbon with prominent superiority in substance affinities and mass transfer for improving the adsorption performance. Herein, the waste-derived carbon (AC-KOH) with multimodal pore structures was successfully synthesized by thermally remodeling the pores of waste hollow fiber membranes collected from sewage-treatment plants. Mechanism study revealed that KOH etching in the original pores of polyvinylidene fluoride (PVDF) film leaves micropores, while the development of meso‑macropores is induced by polyethylene terephthalate (PET) liner pyrolysis and subsequent re-crosslinking and cyclization surrounding KOH. The synergism of macro-meso-micropores enabled the fast diffusion of molecules from the bulk solution to adsorption sites, thereby AC-KOH exhibited fast adsorption kinetics for removing four types of phenolic pollutants and small dye molecules (molecular weight <350 g/mol). More importantly, hierarchically porous AC-KOH displayed a 24 times higher kinetic constant than that of PVDF-AC with mono-micropores for the adsorption of larger Congo red molecules (697 g/mol), with a maximum adsorption capacity of 2519.2 mg/g, which is much higher than many reported adsorbents. This work offers a sustainable way toward waste membrane reutilization and demonstrates a new design strategy for constructing hierarchical pores to overcome the technical challenges of adsorption.