Chemical Fiber Separation Methods

Chemical treatments, such as alkalization, bleaching with sodium hypochlorite (NaClO) or chlorite (NaCl02), are applied on the fiber bxmdles to extract the technical fiber that can stand the loads of tension and torsion. Chemical treatments are effective in removing the extra celulosic materials and exposing the cellulose. However, if the alkalization conditions are too strong, this may cause damage in the fiber [15]. 

Bacci et al. [39] treated nettle stalks with boiling soda solution xmtil the bark, the source of fiber, was easily removed from the core of the stalk than performed alkalization treatment on the bark. Enzymatical fiber retting maybe faster and more reproducible than the traditional biological fiber retting methods and is extensively studied for flax and hemp extraction enhancement [39]. 

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Hollow-fiber ultrafiltration can be a very usefiil tool in obtaining size-fractionated samples for chemical and physical analyses of humic and fulvic acids in surface and groundwaters. The technique is very reproducible because it is strictly a physical separation, it minimizes the potential artifacts associated with the more classical chemical separation techniques. The separation method assumes a spherical structure for the cutoffs and therefore is an empirical approach. Nevertheless, hollow fibers can be used much as 0.45 im filters are used to separate particulate versus dissolved material with a great deal of success. 

Separation of biomass components is the very important initial step for the upcoming efficient utilization of biomass sources. Several physical and chemical separation methods are currently employed to overcome the recalcitrance of lignocelluloses. These methods include acid hydrolysis, alkaline hydrolysis, ammonia fiber expansion, hot water, organic solvent, and ionic liquid separation technologies. In this section of the chapter, all of the above separation methods are discussed. 

The commonly used separator material now is the surface treated polypropylene. The surface treatment helps in making the polypropylene permanently wettable. Surface treatments involve the grafting of a chemical such as acrylic acid to the base fibers to impart wettability and is accomplished using a variety of techniques such as UV or cobalt radiation. Another method of imparting wettability to the polypropylene is a sulfonation treatment where the base fiber material is exposed to fuming sulfuric acid. The separator surface is designed to be made hydrophilic to the electrolyte. 

Reverse osmosis is nsed as a method of desalting seawater, recovering wastewater from paper mill operations, pollution control, industrial water treatment, chemical separations, and food processing. This method involves application of pressure to the surface of a saline solution, thus forcing pure water to pass from the solution through a membrane that is too dense to permit passage of sodium and chlorine ions. Hollow fibers of cellulose acetate or nylon are used as membranes, since their large surface area offers more efficient separation. 

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