Electrospun nanofibers of chitosan/polyvinyl alcohol/UiO-66/nanodiamond: Versatile adsorbents for wastewater remediation and organic dye removal

The appeal of metal–organic frameworks (MOFs) in wastewater treatment is tempered by their polycrystalline, powdery state, and challenges associated with their deployment. In the case of UiO-66, one of the most stable and widely-used MOFs, a low tendency for removing some organic contaminants has been observed on top of the mentioned issues. To address these challenges, herein, we take two complementary steps, i.e., hybridization of UiO-66 with organic nanodiamond (ND) followed by the integration of the hybrid nanoparticles in electrospun polymeric nanofibers based on chitosan/polyvinyl alcohol (PVA). We present the electrospinning of polymer/MOFs as a promising technique to fabricate highly efficient adsorbents for water remediation. We use the electrospun chitosan/PVA nanofibers (ECPN) as a versatile host for MOF nanoparticles that remove cationic methylene blue and anionic Congo red dyes. Four nanofiber composites containing thermally oxidized nanodiamond (TOND), ND, UiO-66, and TOND@UiO-66 are utilized to unravel the effect of nanoparticles type and loading on dye adsorption capacity. It is shown that incorporation of a small loading of nanoparticles in ECPN significantly enhaces the maximum dye adsorption capacity. More importantly, the rationally engineered hybrid TOND@UiO-66 nanoparticles exhibit the best performance in dye adsorption; for instance, an 80 % increase in maximum dye adsorption capacity, from 769 to 1429 mg/g, is recorded for ECPN loaded with TOND@UiO-66 compared to the unfilled ECPN. On top of that, the designed adsorbent showed appreciable regeneration ability after 6 adsorption–desorption cycles. All in all, this study offers a new generation of engineered advanced materials to remove emerging contaminants from water streams.