Silver-loading asymmetric cellulose acetate (CA) hollow fiber membrane was spun via the dry jet-wet spinning technique. The spinning solution was prepared by dissolving AgNO3 and CA in N,N-dimethylformamide (DMF). The silver ions were reduced in the spinning dope into silver nano-particles. The morphology of the resulting hollow fibers was examined using a scanning electron microscope and the silver content in the fiber was measured using an inductively coupled plasma atomic emission spectrometer. The antibacterial activities were evaluated. These hollow fibers had a sponge-like structure and dense inner and outer surfaces. At a 50 k magnification, the pore on the skin layer was not observable, while the nodule size was smaller than 10 nm. The residual silver content of as-spun hollow fiber was about 60% of the original silver added in the polymer solution. After immersing in water bath for 180 days, the silver content in the bulk of the hollow fibers decreased to 60% and the silver content on the surface reduced to 10%, yet still showed antibacterial activity against Escherichia coli and Staphylococcus aureus. After permeating with water for 5 days, the silver content in the hollow fibers decreased, and did not show antibacterial activity against E. coli and S. aureus. Thus, silver content must be periodically replenished after permeation. The proper range of AgNO3 in the spinning solution for CA hollow fiber should be about 100–1000 ppm. Copyright © 2005 John Wiley & Sons, Ltd.

The preparation and characterization of silver-loading cellulose acetate hollow fiber membrane for water treatment

Industrial wastewater often contains different complex impurities that are hazardous to the environment and human health, making wastewater treatment a necessity prior to its disposal This review focuses on cell immobilization in the biological wastewater treatment, in which microorganisms are utilized for the biodegradation and removal of different types of contaminants, depending on the type of contaminat Cell immobilization provides the ability to successfully limit the mobility of the cells using synthetic or natural polymers, which can then be used as biocatalysts instead of free cells We provide a comprehensive evaluation of major cells immobilization aspects, starting from the definition of the technology and focusing on a critical and technical analysis of the currently used immobilization techniques including adsorption, covalent binding, entrapment and encapsulation Biological water treatment systems using immobilized cells have the potential to be utilized in the degradation of various types of wastewater contaminants This resulted in remarkable advances in the immobilization techniques, used materials, and properties of immobilized systems Cell immobilization techniques are becoming well developed, new techniques are being studied by researchers, and the trend of advances in this area is expected to continue increasing in the coming years Studies proved that immobilization is an effective and promising technique to enhance biological wastewater treatment processes Immobilized cells could increase the removal efficiency of water contaminants, particularly nutrients, by more than 60% In this review, the main factors in the development of immobilized cells are highlighted, starting from the selection of immobilization support and providing a detailed description of the immobilization techniques The application of cells immobilization for different wastewater treatment processes is illustrated Different examples of wastewater biotreatment are presented, including refractory organics wastewater, wastewater containing heavy metal ions, nitrogen and phosphorous wastewater as well as the removal of dye and color in textile industry wastewater The review ends with a brief overview of future perspectives of research on cells immobilization

Immobilization of microbial cells for the biotreatment of wastewater: A review

Characterization and inhibitory effect of antibacterial PAN-based hollow fiber loaded with silver nitrate

Degradation of phenol by Rhodococcus erythropolis UPV-1 immobilized on Biolite in a packed-bed reactor.

An immobilized-cell membrane bioreactor was fabricated to investigate degradation of phenol at high concentrations using Pseudomonas putida American Type Culture Collection 49451. In the case of suspension cultures, P. putida utilized phenol at concentrations below 1,000 mg/L, but experienced substrate inhibition at higher concentrations. On the other hand, cells immobilized in 25% by weight polysulfone fibers degraded phenol at concentrations above 1,000 mg/L. At an initial phenol concentration of 1,200 mg/L, phenol was fully degraded within 95 h in the immobilized system, whereas no cell growth and phenol degradation were observed in the free suspension system at 1,000 mg/L phenol. In the immobilized system, it was observed that cells diffused from the membranes when phenol concentrations reached noninhibitory levels in a few experiments. In such cases, the time taken for complete degradation was shorter with cell diffusion because suspension cells were responsible for the rapid phenol degradation. Furt...

Immobilized-Cell Membrane Bioreactor for High-Strength Phenol Wastewater

The objective of this study is to investigate the feasibility of developing cellulose acetate (CA) membranes to partially immobilize Pseudomonas putida (ATCC 49451) and to evaluate the inhibitory effect of phenol on the immobilized bacteria by monitoring their growth in partially immobilized and free-suspension systems. The cellulose acetate membranes used in this study were wet spun from 20 wt % of CA in 1-methyl-2-pyrrolidone (NMP)/acetone (30 : 70) solvent using water as the bore fluid as well as the external coagulant. Scanning-electron microscopy (SEM) characterization of the newly developed CA hollow fibers suggests that the fiber cross section consists of multilayer microporous structures useful for cell immobilization. Experiments were conducted using the bacteria to degrade phenol at initial phenol concentrations of 300 mg/L and 1000 mg/L. In a free suspension (no membrane) system, it was observed that the bacteria were able to grow optimally at 300 mg/L of phenol, and degraded phenol almost completely in about 26 h. However, neither cell growth nor phenol degra- dation occurred when initial concentration of phenol was increased to 1000 mg/L. In a cell-immobilized membrane system, the cell growth and phenol concentration profiles in the medium were very similar to those obtained in a free suspension culture if phenol concentration was 300 mg/L. However, when the initial phenol concentration was increased to 1000 mg/L, data obtained in a cell-immobilized membrane system were discernibly different from that obtained in the suspension culture. In the former case, phenol concentration decreased in the beginning of test, indicating that the carbon source has been consumed and immobilized cells within the membrane had begun to multiply. As soon as the phenol concentration decreased to about 700 mg/L (at which concentration, substrate inhibition was not as severe as 1000 mg/L),partial immobili- zation occurred when some cells diffused out of the membrane into the medium and optical density became measurable in the medium. It was found that cell growth contin- ued for the next 32 h, reaching an optical density in the medium of 0.42 absorbance units and a significant amount of phenol was degraded. q 1998 John Wiley & Sons, Inc.

Sock Khiang Goh

Papers

Development of Cellulose Acetate Membranes for Bacteria Immobilization to Remove Phenol