Impact of functionalized and structurally tuned cellulosic composite membranes on removal of metal ions, dye, drug, and proteins

Abstract

Accomplishing on demand molecular separation with high selectivity and good permeability is desirable for molecules/pollutants, chemical and pharmaceutical processing. The major challenge for sub-micron filtration of particles and molecules in the fabrication of high-performance membranes with tunable pore-size and designed functionality. Here, a top-down approach is demonstrated to produce a membrane using functional and structural tuning. In detail, a composite cellulosic membrane with long pine fiber (LPF) and high-grade cellulosic microfibers (CMF) was fabricated and further tuned by in-situ TEMPO oxidation. The efficacy of this functional tuning was demonstrated by a two-fold increase in surface ζ-potential (-60 mV) and carboxylic group density (133.4 ± 2.1 μmole/g). To test our hypothesis further, functionalized composite membrane was structurally tuned by surface coating route, cellulose nanocrystals (CNC) were coated on oxidized composite membranes, indeed, the coated composite membranes was denser with decrease average pore-size to 0.52μm, furthermore, two-layered (1–1.5 μm coated and a base layer) structure could be easily seen by SEM analysis. Likewise, all fabricated composite membranes were tested for the removal of metal ions (Cr3+ and Mg2+), drug (porphyrin), dye (methyl blue), and proteins (Lysozyme, Cytochrome C, Bovine serum Albumin, Myoglobin). Results illustrates that structural tuned composite membrane was more effective compared to functional tuned one. Charge molecules/pollutants start separation with adsorption followed by molecular sieving. Furthermore, such biobased composite can also be reused and recycled and could have a high impact in circular economy.