Abstract
Porous regenerated cellulose (RC) membranes were prepared with cotton linter pulp as a raw material. These membranes were first oxidized on both sides by a modified (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation system using a controlled oxidation reaction technique. Then, the oxidized RC membranes were functionalized with polyethylenimine (PEI) via the glutaraldehyde crosslinking method to obtain bifunctional (carboxyl and amino) porous RC membranes, as revealed by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and zeta potential measurement. The scanning electron microscopy (SEM) and the tests of the mechanical properties and permeability characteristics of modified RC membranes demonstrated that the porous structure and certain mechanical properties could be retained. The adsorption performance of the modified membranes towards dyes was subsequently investigated. The modified membranes displayed good adsorption capacities, rapid adsorption equilibrium and removal efficiencies towards both anionic (xylenol orange (XO)) and cationic (methylene blue (MB)) dyes, making them suitable bioadsorbents for wastewater treatment.
Highlights
Synthetic dyes are widely utilized in numerous industries owing to their high stability, relatively low costs and color uniformity characteristics [1,2]
Compared with the unmodified regenerated cellulose (RC), the FTIR spectra of the TEMPO-oxidized regenerated cellulose (TORC) membranes showed a new peak at 1736 cm−1, which was attributed to the C=O stretching frequency of the carboxyl group [32], thereby revealing a successful TEMPO-oxidation process
In the case of the PEI-TORC membranes, new absorption bands were observed at ca. 1653 cm−1 corresponding to the C=N stretching vibration, which was formed in the glutaraldehyde crosslinking process
Summary
Synthetic dyes are widely utilized in numerous industries (e.g., textile, paper, leather tanning, plastics, rubber, cosmetics and printing) owing to their high stability, relatively low costs and color uniformity characteristics [1,2]. Biodegradable and biocompatible cellulose-based materials have been developed in recent decades taking advantage of the wide availability (i.e., the most abundant renewable biopolymer in nature) and low cost characteristics of this polymer. These materials have been used for water treatment purposes especially, as a new class of versatile adsorbents for the removal of dyes. During the modification process, celluloses are often subjected to strong acid or oxidant, etc., treatments, so leading to the degradation of cellulose macromolecules [24], which further may damage the porous structures of the cellulose membranes and even destroy membranes themselves These facts can significantly limit the application of cellulose membranes for adsorption purposes. With the aim to further evaluate the potential application of the modified RC membranes for water treatment purposes, the porosity, pure water permeability characteristics and the mechanical properties of the modified RC membranes were tested
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