Sustainable Novel Bamboo-Based Membranes for Water Treatment Fabricated by Regeneration of Bamboo Waste Fibers

The waste fiber byproduct of the bamboo construction industry was used as the sustainable feedstock for the fabrication of cellulose-based membranes using 1-butyl-3-methylimidazolium chloride [C4mim]­[Cl]­([C4mim]­[Cl]) ionic liquid (IL) as a “green” and environmentally friendly solvent. The lignin and hemicellulose fractions of the bamboo waste fibers were removed, and the extracted cellulose was used at different concentrations (3, 5, and 10 wt %) for the fabrication of membranes using the phase inversion technique. The intrinsic properties of the fabricated membranes such as morphology, crystallinity, surface charge, roughness, and chemistry were characterized using scanning electron microscopy, powder X-ray diffraction (XRD), zeta potential, atomic force microscopy (AFM), and water contact angle, respectively. The transformation of cellulose I to cellulose II with a different crystallinity index was observed for each membrane based on the initial concentration of cellulose digested by [C4mim]­[Cl]. The performances of the bamboo-based membranes in the removal of different dyes (methylene blue, methylene orange, and crystal violet) from water were studied regarding membrane permeance, antifouling, and rejection. In general, the bamboo-based membranes performed similarly or better than comparable cellulose-based membranes in water flux, antifouling, and rejection, which confirmed the successful conversion process of waste materials (bamboo waste fibers) to a high-value-added product (membrane) through sustainable green technology. The size exclusion was observed as the main mechanism for dye rejection, and solute diffusion was identified as the dominant transport mechanism through the bamboo-based membranes. The physical membrane structure (dense layer) and the dye size were the two governing factors of rejection, and the surface charge and hydrophilicity are the governing factors of the antifouling capability of the membranes. The 10% bamboo-based membranes and 3% bamboo-based membranes showed the highest dye rejection (87%) and water flux 600 LMH, respectively.