Alternating spin-and-spray electrospun scaffold membranes with fractionated MIL-101(Cr) adsorbent for high-performance single-pass dye adsorption process

Abstract

Adsorption is an attractive process for wastewater treatment, owing to its technical simplicity and ease of implementation. However, the adsorption process is often challenged by unoptimized efficiency, especially when the high-performing adsorbents are compacted into a packed bed column design. Herein, an electrospun nanofibrous porous scaffold is rationally designed to fractionate packing and reduce hydraulic resistance of a chromium benzene dicarboxylate-based metal–organic framework (MIL-101(Cr)) used as an adsorbent for the removal of anionic dyes. The MIL-101(Cr) adsorbent was in situ loaded via a spray-assisted method onto the electrospun scaffold in an alternating spray-and-spin fashion to deconstruct the packing and offer fractionated loading of the adsorbent materials. As compared to its unfractionated counterpart, well-fractionated MIL-101(Cr) exhibited an order of magnitude higher adsorption capacity over time with high dye removal towards Methyl Orange (MO), Acid Fuchsine (AF,) and Rose Bengal (RB). In a single pass filtration experiment, the PAN/MOF(50) ESNF-AS scaffold performed at 8808, 5066, and 7574 Lm−2h−1bar−1 water permeabilities at 2 psi with exceptional > 99 % dye removal for MO, AF, and RB dye, respectively. In addition, the spent MIL-101(Cr) adsorbent in the electrospun scaffold was able to be regenerated by alkaline and acid washing and showed good recyclability, suggesting the chemical and structural robustness of the scaffold design. This approach is highly versatile and can be adopted on different adsorbents to target the removal of different contaminants from wastewaters for a more sustainable future.