TEMPO-oxidized and carbon dots bound cellulosic nanostructured composite for sustainable fully biobased membranes for separation of nano/micro-sized particles/molecules

Membrane separation is a highly energy-efficient method for eliminating pollutants, ranging from micrometer-sized particles to angstrom-sized hydrated ions, from water. Nevertheless, the existing membrane technology , which uses costly synthetic materials, has become unsustainable for the most impoverished populations in the society. Thus, in the present study, a fully biobased sustainable functional membrane was developed for the effective separation of impurities from wastewater. A 2,2,6,6-Tetramethylpiperidin-1-oxyl (TEMPO) oxidation and integration of carbon dots (CDs) to cellulose nanofiber (CNF), resulted in significant improvements in the functional properties of membranes. The effectiveness of this modification resulted in a remarkable augmentation in surface ζ-potential as –68.5 mV for pristine CNF to −102 mV for CDs blended CNF. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) studies confirmed the existence of essential functional groups that enabled better interactions within the composite membranes . The functionalization of CNF membranes resulted slightly lower in water flux from 1536 L/m 2 /h for pristine membranes and 1089 L/m 2 /h for TEMPOoxidized and 1402 L/m 2 /h for CDs integrated membranes. This hypothesis further confirmed that the tuned membranes were denser with a decreased pore size of 19.96 Å for pristine and 17.49 Å for TEMPO functionalized CNF membranes. We demonstrated that functionalized cellulose nanofiber membranes have high filtration efficiency for heavy metals (Fe 3+ , Cu 2+ ), dyes (methylene blue and dyes from garment industry wastewater), and protein (bovine serum albumin). Moreover, such biobased composite membranes can be reused, thereby exerting a significant influence on the circular economy.