Preparation and Application of Chitosan-Based Membrane: Focusing on Dye Removal

Abstract

AbstractWater pollution is caused by the direct discharge of harmful dyes into the environment and is a major global problem. Dyes if present in the water can be toxic to the aquatic organisms and humans. Dyes are recalcitrant in nature, and they can resist attack by heat, light, and microorganisms. Hence, most of the reactive dyes are non-biodegradable and their removal from the aqueous solution is very difficult, and therefore, a necessary measure must be applied in order to tackle the existence of the water pollution problem. Adsorption is a well-known technology that is adopted in the academia and industries for removal of dyes from solution. The adsorption of dyes on adsorbents is a simple and economical procedure that is widely used for large and small-scale removal of dyes. In the current chapter, we reviewed the extraction of chitin from the shells of marine animals, the preparation of chitosan by deacetylation reaction, structure and properties of the chitosan biopolymer. Chitosan films could be prepared by casting technology via dissolution of chitosan in a suitable solvent followed by simple evaporation technique. The chapter highlights that chitosan films have superior physicochemical characteristics than raw chitosan biopolymer; the mechanical strength of reported chitosan films might be as high as 28 MPa. Among the different chitosan films, this chapter has comprehensively presented the discussion on preparation, characterization, and dye removal application of various classes of chitosan composite membranes. The tensile strength of chitosan composite film could reach 35 MPa approximately, thus suggesting the composite films based on chitosan could be considered as good adsorbents for dye removals from water. The maximum adsorption capacity (Qmax) of the reviewed composite film could reach 655 mg g−1, but comparatively lower than Qmax of chitosan-magnetic cyclodextrin composite by a mammoth difference of 2125 mg g−1. Both of the chitosan-based composites are recyclable through multiple adsorption–desorption cycles. Despite the good adsorption and regeneration and reuse capabilities of chitosan-based composite films, and in order to enhance their dye removal capacities, the present chapter has strongly recommended further works to explore more of magnetic chitosan-based composite membranes with superior adsorptive behaviors for consideration of future practical dye removal application from wastewater. Finally, the characterizations of such adsorbent systems should be comprehensively investigated before and after dye removal to understand the details on mechanism of the removal of dyes from water.KeywordsWater pollutionChitosanChitosan filmsChitosan composite membranesTensile strengthAdsorptive behaviorDyes removalMaximum adsorption capacity (Qmax)MechanismRecycling