Preparation and performance of homogeneous braid reinforced cellulose acetate hollow fiber membranes

Homogeneous braid reinforced (HBR) cellulose acetate (CA) hollow fiber membranes were fabricated through dry-wet spinning process which consisted of CA separation layer and CA hollow tubular braids. The performance of various CA concentration membranes were characterized in terms of pore size distribution, pure water flux (PWF), protein solution flux (PSF), mechanical strength, and membrane morphologies were observed by a scanning electron microscope. The results showed that the HBR CA hollow fiber membranes, especially with high CA concentration in the dope solutions, possessed dense and smooth outer surface. The tensile strength of HBR CA hollow fiber membranes which exceeded 11 MPa mainly depended on the tubular braids. With the increase of CA concentration, the tensile strength and bursting strength of the membranes increased. In addition, there was effective interfacial bonding state between the separation layer and the tubular braid when the CA concentration was higher than 10 wt%. The increase of CA concentration brought about the decrease of membrane pore size and the increase of protein rejection. Considering the PWF, rejection and stable PSF, the best CA concentration in the dope solutions was 10 wt%. Then the membrane fouling and cleaning processes for the activated sludge solution were studied by comparing with reinforced polyvinylidene fluoride (PVDF) hollow fiber membrane. The lower flux decline in the filtration of activated sludge solution and higher recovery in the flux indicated that the HBR CA hollow fiber membrane had better anti-fouling properties than the PVDF membrane.