**1. Introduction**

A separation process, which is often called the "downstream process", plays a key role of product manufacturing through chemical or biochemical reaction as well as a synthesis process called the "upstream process" [1]. To ensure quality and cost of final products, the separation process is important and has been developed in line with the social demands [2]. For chemical and biochemical industries, the separation process aims to purify objective substances, eliminate undesirable substances, and fractionate each component from their mixture. As environmental awareness around the world increases recently, new separation technologies, such as wastewater treatment [3], advanced desalination [4], air cleaning [5] *etc.*, are in great demand. In addition, materials used in such separation processes are not only expected to be efficient, low cost, easy operation, but also required to be environmentally-friendly.

Chitin and chitosan obtained from crustaceans possess sufficient environmental adaptability as well as an attractive potential to build various types of functional media, e.g., membranes [6–10], micro/nanoparticles [11, 12], and nanofibers [13–16]. Many studies have devoted to develop the novel media adapting separation processes using chitosan. The separation performance of such chitosan media should be strongly influenced from chemical properties characterized by deacetylation degree (*DD*) at amino groups in the chitosan molecular chain. Nevertheless, it was less mentioned that the *DD* could steer not only the structure of the prepared chitosan gels but also the characteristics as separation media.

This chapter describes the preparation and physicochemical properties of novel chitosan-based media and demonstrates the promising ability of chitosan with focus on principal studies for environmentally-friendly separation processes. The essential factors which regulate the performance of separation media prepared from chitosan, such as *DD*, molecular weight, and options of cross-linker, are explained. In particular, the notable impacts of *DD* on the mass transfer mediated by chitosan membrane, the mechanical property, and the antibacterial activity, are introduced based on our previous research [17–19]. Separation media prepared from chitosan are often combined with various adsorbents [20, 21], carbon nanotubes [22, 23], or other functional materials [24, 25]. In such case, the behavior of mass transfer into the chitosan hydrogel is complicated to quantitatively evaluate. The present chapter shows the determination of effective diffusion coefficient of cesium ions in chitosan membrane immobilizing Prussian Blue particles [20]. Furthermore, the chitosan aerogels with macro-porous structure is proposed for selective separation for anionic dye from aqueous phase. Chitosan nanofibers incorporated with polyethylene terephthalate (PET) non–woven are also covered to describe in an application of air filtration.

poly(β-(1 ! 4)-*N*-Acetyl-D-glucosamine). Chitosan, poly(β-(1 ! 4)-D-

*Chemical conversion among chitin, chitosan, and furthermore functional separation media.*

activity, antioxidant properties, and an affinity for proteins [7, 26].

formation of a water-insoluble gel structure without cross-linker due to

ation of amino groups in glucosamine units.

*DOI: http://dx.doi.org/10.5772/intechopen.95839*

typical examples [10, 32, 33].

**2.2 Deacetylation degree**

**203**

**Figure 1.**

glucosamine), is obtained mainly by transforming partial deacetylation of chitin in an alkaline condition, such as using sodium hydroxide aqueous solution. It has been reported that chitosan and its oligosaccharides not only possess hydrophilicity, nontoxicity, biodegradability, and biocompatibility, but also possess antimicrobial

*Innovative Separation Technology Utilizing Marine Bioresources: Multifaceted Development…*

Chitosan is insoluble in water at neutral pH or in any organic solvent. Consequently, an acidic aqueous solution, such as acetate buffer solution, is usually employed to dissolve chitosan, whereby the acid dissociation constant of chitosan is found as pKa ≈ 6.5 [30]. Chitosan can be dissolved in acidic solutions by proton-

Deprotonating a chitosan solution through an acid–base neutralization leads to

intermolecular hydrogen bonding [8]. The salt (*e.g.* NaCl) coexisting with chitosan in an acidic solution acts as counter ions and disrupts intramolecular hydrogen bonding, and then the flexibility of chitosan molecular chains increases [31]. In addition, pH neutralization influences the formation of a polymeric network [9]. Therefore, the neutralization condition should be optimized. From the convenient gelling process, chitosan hydrogels have been developed widely as immobilizing matrices, with enzymes, carbon nanotubes, and electroconductive polymers as

Deacetylation degree (*DD*) is the most important factor to regulate physicochemical properties. The deacetylation degree of chitosan samples was determined using the colloidal titration method-based experimental conditions in previous works [34, 35]. We dissolved chitosan powder (0.5 g) in 5% acetic acid solution, and then increased the total weight of chitosan–acetic acid solution to 100.0 g by adding acetic acid. We mixed a 1 g sample of this chitosan–acetic acid solution to 30 ml of deionized water. The titrant was 0.0025 N potassium polyvinyl sulfate (PVS-K), and the indicator was 1% toluidine blue. The terminal point of titration was clearly
