A novel method of cellulose membrane fabrication and its applications.

摘要

Membranes are primarily used for separations. Compared with conventional separation processes, membrane separation processes are often more capital and energy efficient. Cellulose is one of the most popular materials in membrane fabrication industries for its natural and re-usable characteristics. However, the process of dissolving cellulose is challenging. In manufacturing, the viscose process is widely used in cellulose dissolution, which is known as toxic to the environment. Recently, some researches studied the dissolution ability of NaOH toward low DP(degree of polymerization) cellulose, and microcrystalline cellulose was found able to be dissolved in aqueous NaOH. The dissolution process was simple and environmentally acceptable. The dissolving capacity of the aqueous NaOH system coupled with a novel freeze-thaw method towards microcrystalline cellulose has been studied. An optimal condition to successfully dissolve cellulose could hence be determined among those investigations.; The optimal cellulose dissolution condition was then applied to cellulose product fabrication. A novel technique to fabricate semi-permeable cellulose membrane by employing an environmentally friendly cellulose dissolution process is developed. The newly fabricated membrane was subjected to an ultrafiltration process in which membrane properties, water permeation rate and separation performance were determined. By coordinating separation tests of molecular selectivity, this new membrane demonstrated the ability to sieve molecules above MWCO (molecular weight cutoff) 50,000. This new membrane was also fabricated into different morphologies and introduced to the real applications, e.g., protein purification and concentration. The results indicated that this new membrane could achieve the separation goals as commercial membranes did.; In addition, the cellulose regeneration process was derived to make cellulose particles with drug encapsulated, which could be used as the drug carrier in oral administration or enzyme immobilization. Without polymerization, cellulose mirobeads with drugs loaded could be produced specifically by water-in-oil dispersion and cellulose regeneration. These drug containing particles were characterized from drug release profiles and by studying the release kinetics. From the drug release results, regenerated cellulose and this microencapsulation method reveals their high potential been applied in enzyme immobilization and drug delivery.