A novel method to prepare high chitosan content blend hollow fiber membranes using a non-acidic dope solvent for highly enhanced adsorptive performance

A novel method was developed to prepare chitosan (CS) and cellulose acetate (CA) blend hollow fibers with high CS contents as adsorptive membranes through the use of a non-acidic organic dope solvent. CS was synthesized into nano-particles (about 50-150 nm) by the addition of a surfactant, sodium dodecyl sulfate (SDS), into a CS solution. The CS/SDS nano-particles were dispersed uniformly into a common non-acidic organic solvent, N-methyl-2-pyrrolidone (NMP) that subsequently dissolved CA as the matrix polymer to obtain the CS/CA blend dope solution for spinning the blend hollow fibers. A high CS content was achieved in the blend dope solution (up to 5 wt%) and thus in the resultant blend hollow fibers (up to 29.4 wt%) with water being used as a cheap and effective coagulant. FTIR analysis indicated that SDS interacted with CS and made it dispersible in non-acidic organic solvents, such as NMP. SEM observation showed that the blend hollow fibers had highly porous and macrovoids-free structures and material test confirmed the reasonably good mechanical strength of the blend hollow fibers (e.g., tensile stress at break greater than 1-2 MPa). Adsorption study for copper ion removal demonstrated the high adsorption capacity of the blend hollow fibers (up to 31 mg Cu2+/g blend hollow fibers or 105.4 mg Cu2+ in terms of per gram CS at pH 5), attributed to the high CS content and, possibly, improved accessibility of CS in the blend hollow fiber membranes. The new preparation method provides the great advantage of making high CS content blend hollow fiber membranes with potentially more choice of polymers as the matrix polymer to achieve enhanced adsorption capacity, improved material property and reduced preparation cost. (c) 2007 Elsevier B.V. All rights reserved.