Chitosan Based Membranes for Separation, Pervaporation and Fuel Cell Applications: Recent Developments

Abstract

Growing public health and environmental awareness accompanied by increasing number of stricter environmental regulations on wastes discharge. Attention has been focused on the use of biopolymers from renewable resources as alternatives to synthetic polymers [1]. Biopolymers are produced in nature by living organisms and plants, participate in the natural biocycle and are eventually degraded and reabsorbed in nature. The most widespread biopolymers are polysaccharides among them chitosan(CS) is most valuable, whose swellability in water and viscous solution/gel-forming properties were utilized by manufacture for number of industrial and consumer products. CS (primary derivative of chitin) is commercially available basic polysaccharide [2,3]. The basicity of CS responsible for singular chemical and biological characteristics, biocompatibility, antibacterial properties, heavy metal ion chelation ability, gel-forming properties, hydrophilicity, affinity to proteins and good membrane forming capability. In this chapter we will discuss for modification of CS and its exploitation for advance membrane separation applications. The membrane processes were classified by Howell includes [4]: 1. Cleaner industrial process: adsorption, ultrafiltration and electro-ultrafiltration. 2. Energy: fuel cell applications 3. Pervaporation: separation of organic solvents from their azeotropic mixtures. 4. Water: virus–free supply, water reuse and micro-pollutant-free water Chitosan is obtained by varied extent N-deacetylation and characterized by degree of deacetylation (Fig. 1). It is a copolymer of N-acetyl glucosamine and glucosamine and insoluble in water. CS readily dissolves in acidic solutions due to the presence of amino groups and 80–85% degree of deacetylation is necessary to obtain a soluble product. Commercially, CS is obtained from low cost shells of shellfish (mainly crabs, shrimps, lobsters and krills), the wastes of the seafood processing industry [2-6]. Chemical and biological properties of CS attributable to the presence of amino and hydroxyl groups [2,3,58]. These groups allow chemical modifications of chitosan: acylation, N-phthaloylation, tosylation, alkylation, Schiff base formation, reductive alkylation, O-carboxymethylation, Ncarboxyalkylation, silylation, and graft copolymerization [3,9]. Modifications of CS will help